Issuu on Google+

Data Processing For Technical Students Written by Barr N. Maurice

Systems Engineer

First Edition

1


BRIEF CONTENTS Introduction: Data processing basics

3

Chapter 1: Computer Basics

4

Chapter 2: Hardware and Software basics

8

Chapter 3: Input, Processing, Output and Storage

18

Chapter 4: Communication basics

38

Chapter 5: Programming Basics

49

Chapter 6: Applications 50 Chapter 7: Digital Systems

63

Questions and Answers

66

2


INTRODUCTION What Is Data Processing

Data Processing can be sub divided into Data and Processing so as to ease its interpretation. Generally data is widely used in our day to day activity, references and situations such as a database, a databank ,a data center etc. but it is always good to know exactly what data is all about and how it is link to these situations. Data comes from a Latin word Datum which means something e.g. a piece of information, and it’s now used as a singular where it means “information�. So we can Define Data as raw facts and figures which have no meaning and have not been put into a context (given a purpose) e.g. This is a set of data: 85, 60, 65, 90, 70, 50, 40. As it is, it has no meaning; the numbers could mean anything (within reason). As for Processing it is a series of steps taken in order to achieve a particular end e.g. the process for a computer to boot to the desktop generally have some steps that it has to follow before the user finally click on My Computer on the desktop. So from these divisions above, we can confidently define data processing as: The steps or series of steps taken in order for data which are the raw facts with no meaning to be massaged ,converted to understandable information or given a purpose. We should not be confuse with Word Processing which on the other end are the series of steps taken for a series of text strings,images,numbers to be formatted (arranged) to understandable, readable and presentable form. E.g. formatting an Income Statement Document, Formatting Curriculum Vitae etc. Data Processing is the back-bone of ICT (Information and Communication Technology) and we must know that the development of an ideal information system heavily rely on a good and sound knowledge in Data Processing. These steps in data transformation and modification will need other elements which we are going to explain as we are going deeper into the subject. Before we get further into this topic , we must first touched other elements that relates and contribute to data processing as a whole such as knowing exactly what a computer is all about, categories of computers ,generations , hardware and software , storage devices,network,Computer Programming ,Spreadsheet Application and Word Processing Applications and lastly we have to talk much about Relational,Flat,Hierachical and other database concepts . In data processing we shall talk much about the different elements or components that make up data processing , and we shall also differentiate between data processing and electronic data processing , which is the use of data processing tools such as excel to process and format data that can be used in transactional matters such as a stock manager created in Excel , creating an account or debiting an account in Le Sage System software and creating a student enrollment database in Microsoft access are the various components of electronic data processing . Notwithstanding, data processing merge our Computer science and data/information to justify the users processes and conversion of raw facts into useful information.

3


Chapter 1 COMPUTER BASICS Before we delve into this chapter, it is good that we do some junior computer lessons such as knowing what a computer is all about, characteristics, input and output devices, computer peripherals, memory and much more. This will go a long way in strengthening and increasing our knowledge on this topic. Before now , Computers where considered a mysterious device , used by Aliens or very intelligent beings as we can call them for some time travel or complex experiments, and we even considered those who used these devices to be so intelligence , which at lesser extend was true since the first models needed so much expertise. But nowadays we can spot a computer unit everywhere, in bookshops, banks, provision stores, government offices, schools and most importantly in every home. It is now considered an inevitable device to own. We have computers in various sizes, colors, design, speed, prices and so on, but the fact remains that it is an electronic device with immense potential and use. 1.1 What is a Computer? A computer is an electronic device that executes the instructions in a program. To expatiate this definition, a computer is an electronic device for storing and processing data, typically in binary form, according to instructions given to it in a variable program. From the definition, calling a computer an electronic device automatically tells us that it has small components such as microchips and transistors that control and direct electric current and hence without current a computer cannot function. And further more talking of the fact that a computer is capable of storing and processing data , shows how complex in nature a computer is , and its use in our day to day operation as calculator, a messenger and so on and so forth . A typical computer has four basic functions:    

Accept Data – Input Processes Data – Processing Produces Output – Output Stores Results – Storage We generally term the above functions of a computer an Information Cycle as such all computer or generally all electronic devices performs this functions in a cyclical manner such as , you must input information such as scanning a picture to edit and store or print it out later, for a calculator, you must input values so that the calculator calculates it and prints out the result .

Input

Processing

Storage Output The Information Processing Cycle

Some Beginning Terms 4


It is always good to correctly understand a term in Computer so that you can match it to particular term and not confuse it with a similar term. So in our basics, we are going to explain some common terms we shall be using most often. 1. Hardware: The physical parts of the computer. E.g. we have the monitor, the Mouse, the Keyboard, the CD/DVD ROM, the RAM, the Processor, Floppy Disk, The Hard drive, the extension cards such as Sound Card, Video Card, USB Card, etc. 2. Software: The programs (instructions) that tell the computer what to do such as Microsoft Office Package, Le Sage, the Operating System etc. 3. Data: Individual facts like first name, price, quantity ordered 4. Information: data which has been massaged into a useful form, like a complete mailing address 5. Default: the original settings; what will happen if you don't change anything.

1.2 What makes a computer powerful? Sometimes it is always good to ask yourself the question, how is it possible for a computer to do complex task at so little time. Imagine sending an email from Cameroon to a relative who lives in Maryland USA, as you finish typing your mail, as soon as you click on send , your relative immediately receives the mail ,just like magic isn’t it ?. The process from above to decrypt it is as complex as the universe itself as there are millions if not billions of different task that mail has to complete before arriving and be read at the other end of the world. Well, let’s not worry about the process but the possibility of the computer to be that complex. a) Speed: A computer can do billions of actions per second, thus it is capable of not only handling one task at a time, but also to handle so many task or processes at a time called Multitasking by a single computer processor. Talking about speed, the computer’s processor generally handles this aspect by being able to do so many operations, calculations generally refer to as its arithmetic and logic control (ALU) and also being able to register these tasks at amazing frequencies generally calculated as a frequency of time and measured in Hertz, Megahertz, Gigahertz with recent processors called Duo (two), the i5 and i7 that runs at very terrific speeds. b) Reliability: Apart of its speed, a computer is very reliable in its activities such as calculations, timing, and statistical values and much more. The only problem is that, if wrong information in inputted into the computer, definitely wrong information will be sent out i.e. garbage in, garbage out. So that’s why we have to learn how to use a computer and its related programs. c) Storage: The computer is capable of storing huge amount of information, and easily releases this information for further use. The unit in a computer for storage are divided into some sub units such as primary storage devices like RAM (Random access memory) which is often refer to as a Volatile storage meaning that information is loss as soon as there is no current and the Secondary Storage like the Floppy Diskettes, Hard Drives,CD-ROMS/DVDROMS which are referred to as Nonvolatile Storage meaning that information stored remains intact even when there is no current . Optical disc are part of this Secondary storage devices and they are referred to as optical because there require electromagnetic radiation for their operation. The unit of storage in Computer is measured in Bytes which refers to 8 bits and ranges from Megabytes = 1000000 bytes GigaByte = 1000000000 bytes TeraByte = 1000000000000 bytes

5


A. PERSONAL OR MICRO COMPUTER

Computers for personal use come in all shapes and sizes, from tiny PDAs (personal digital assistant) and smart phones to hefty PC (personal computer) towers. More specialized models are announced each week - trip planners, expense account pads, language translators... To make things even more interesting, categories are blending together. Phones are getting really,

really smart. Fig. 1 Descriptions of Personal Computers When talking about personal computers (PCs), most people probably think of the desktop type, which are designed to sit on your desk. (Bet you figured that one out!) The tower and the smaller mid- and mini-tower style cases have become popular as people started needing more room for extra drives inside. Repairmen certainly appreciate the roominess inside for all the cables and circuit boards ... and their knuckles. A workstation is part of a computer network and generally would be expected to have more than a regular desktop PC of most everything, like memory, storage space, and speed. It's hard to tell the difference any more. A variety of laptops/notebooks and similar PCs, like the netbook, that serve as a middle ground between the bulkier, heavier desktops and the extreme portability of PPCs, HPCs, and smart phones. A laptop computer is intended to be portable, with a built-in screen. A netbook is even lighter, with a smaller screen, less storage, and is missing features like a built-in DVD drive. Companies keep improving features and components, like laptop batteries, and are producing more varieties and styles of these smaller computers daily, or so it seems. The market for the smallest PCs is expanding rapidly. Simplified versions of your regular software are becoming available for the small types of PC like the palmtop (PPC) and handheld (HPC) and for smart phones. You can carry a tiny computer like a Palm Pilot, Blackberry, or a smart phone around and enter new phone numbers and appointments and those great ideas you just had. Later you can move this information to your main computer. More and more of these small devices can connect wirelessly to the Internet. Using web applications, like Google Docs and Microsoft Office Web Apps, you can use a browser to view and even edit documents that are stored online, and, of course, check your email. No local program is required! You just need a data plan that you can afford! With a Tablet PC you use an electronic stylus to write on the screen, just like with a pen and paper, only your words are in digital ink. The Tablet PC saves your work just like you wrote it (as a picture), or you can let the Hand Recognition (HR) software turn your chicken-scratches into regular text. Your second grade teacher was right. Good handwriting is important!

Fig. 2 Mini and Micro Computers B. Main Frame The main frame is the workhorse of the business world. A main frame is the heart of a network of computers or terminals which allows hundreds of people to work at the same time on the same data. It requires a special environment - cold and dry. Most main frame computers look like a bunch of tall cabinets. Not very exciting. These where the first category of Computers 6


designed and used tremendous amount of power for its large parts and needed experts to work on which was a serious down side of this model as compared to the personal computer which is portable, easy to manage and energy efficient.

Fig. 3 Main Frame Computer C - Supercomputers The supercomputer is the top of the heap in power and expense. These are used for jobs that take massive amounts of calculating, like weather forecasting, engineering design and testing, serious decryption, economic forecasting, etc.

Fig. 4 Supercomputer Topic Questions 1. Differentiate between Software and Hardware. - Software are the programs or instructions that permits a computer to function and a hardware are those physical parts that makes up a computer and can be touched. 2. Classify Computers according to their speed and size. - Super Computer, Mainframe, Mini and Micro Computers 3. Give two examples of portable devices - Laptop and netbook and even smartphones can be termed portable devices. 4. What makes computers so powerful? - Speed, Reliability and Storage capacity 5. Give one difference between data and information? - Data is raw facts and information is transformed data

7


Chapter 2 HARDWARE AND SOFTWARE Following along from chapter one , we introduced what a computer is , what makes a computer to possess such power in calculation and also we talked about different types of computers such as Mini and Microcomputers, Main frames and Super Computer . In this chapter we are going to talk about Hardware and Software and clearly define what differentiates them from one another and we are going to also talk about input, output and processing devices. 2.1 What is Computer Hardware? A computer hardware are the machines, wiring , and other physical components of a computer or other electronic system which are visible and sometimes can be physically touched or move about e.g. Memory,Processor,DVD-ROM ,CD-ROM, Casing etc. The Hardware is what defined an electronic device as without these components, all the programs written can’t be executed nor installed, and we can also say that it is the backbone or skeleton of the electronic world. In a computer, we have several components that are coupled together make up a computer unit such as; a) The motherboard: which is a printed circuit board containing the principal components of a microcomputer or other device, with connectors into which other circuit boards can be slotted. b) Central Processing Unit - Though the term relates to a specific chip or the processor a CPU's performance is determined by the rest of the computer's circuitry and chips. Currently the Pentium chip or processor, made by Intel, is the most common CPU though there are many other companies that produce processors for personal computers. Examples are the CPU made by Motorola and AMD.

With faster processors the clock speed becomes more important. Compared to some of the first computers which operated at below 30 megahertz (MHz) the Pentium chips began at 75 MHz in the late 1990's. Speeds now exceed 3000+ MHz or 3 gigahertz (GHz) and different chip manufacturers use different measuring standards (check your local computer store for the latest speed). It depends on the circuit board that the chip is housed in, or the motherboard, as to whether you are able to upgrade to a faster chip. The motherboard contains the circuitry and connections that allow the various components to communicate with each other. c) Keyboard - The keyboard is used to type information into the computer or input information. There are many different keyboard layouts and sizes with the most common for Latin based languages being the QWERTY layout (named for the first 6 keys). The standard keyboard has 101 keys. Notebooks have embedded keys accessible by special keys or by pressing key combinations (CTRL or Command and P for example). Ergonomically designed keyboards are designed to make typing easier. Hand held devices have various and different keyboard configurations and touch screens. Some of the keys have a special use. They are referred to as command keys. The 3 most common are the Control (CTRL), Alternate (Alt) and the Shift keys though there can be more (the Windows key for example or the Command key). Each key on a standard keyboard has one or two characters. Press the key to get the lower character and hold Shift to get the upper. Others include AZERTY layout etc. d) Removable Storage and/or Disk Drives - All disks need a drive to get information off - or read - and put information on the disk - or write. Each drive is designed for a specific type of disk whether it is a CD, DVD, hard disk or floppy. Often the term 'disk' and 'drive' are used to describe the same thing but it helps to understand that the 8


e)

f)

g)

h)

i)

disk is the storage device which contains computer files - or software - and the drive is the mechanism that runs the disk. Digital flash drives work slightly differently as they use memory cards to store information so there are no moving parts. Digital cameras also use Flash memory cards to store information, in this case photographs. Hand held devices use digital drives and many also use removable or built in memory cards. Mouse - Most modern computers today are run using a mouse controlled pointer. Generally if the mouse has two buttons the left one is used to select objects and text and the right one is used to access menus. If the mouse has one button (Mac for instance) it controls all the activity and a mouse with a third button can be used by specific software programs. One type of mouse has a round ball under the bottom of the mouse that rolls and turns two wheels which control the direction of the pointer on the screen. Another type of mouse uses an optical system to track the movement of the mouse. Laptop computers use touch pads, buttons and other devices to control the pointer. Hand helds use a combination of devices to control the pointer, including touch screens. Note: It is important to clean the mouse periodically, particularly if it becomes sluggish. A ball type mouse has a small circular panel that can be opened, allowing you to remove the ball. Lint can be removed carefully with a tooth pick or tweezers and the ball can be washed with mild detergent. A build up will accumulate on the small wheels in the mouse. Use a small instrument or finger nail to scrape it off taking care not to scratch the wheels. Track balls can be cleaned much like a mouse and touch-pad can be wiped with a clean, damp cloth. An optical mouse can accumulate material from the surface that it is in contact with which can be removed with a finger nail or small instrument. Monitors - The monitor shows information on the screen when you type. This is called outputting information. When the computer needs more information it will display a message on the screen, usually through a dialog box. Monitors come in many types and sizes. The resolution of the monitor determines the sharpness of the screen. The resolution can be adjusted to control the screen's display.. Most desktop computers use a monitor with a cathode tube or liquid crystal display. Most notebooks use a liquid crystal display monitor. To get the full benefit of today's software with full colour graphics and animation, computers need a color monitor with a display or graphics card. Printers - The printer takes the information on your screen and transfers it to paper or a hard copy. There are many different types of printers with various levels of quality. The three basic types of printer are; dot matrix, inkjet, and laser.  Dot matrix printers work like a typewriter transferring ink from a ribbon to paper with a series or 'matrix' of tiny pins.  Ink jet printers work like dot matrix printers but fires a stream of ink from a cartridge directly onto the paper.  Laser printers use the same technology as a photocopier using heat to transfer toner onto paper. Modem - A modem is used to translate information transferred through telephone lines, cable, satellite or line-of-sight wireless. The term stands for modulate and demodulate which changes the signal from digital, which computers use, to analog, which telephones use and then back again. Digital modems transfer digital information directly without changing to analog. Modems are measured by the speed that the information is transferred. The measuring tool is called the baud rate. Originally modems worked at speeds below 2400 baud but today analog speeds of 56,000 are standard. Cable, wireless or digital subscriber lines can transfer information much faster with rates of 300,000 baud and up. Modems also use Error Correction which corrects for transmission errors by constantly checking whether the information was received properly or not and Compression which allows for faster data transfer rates. Information is transferred in packets. Each packet is checked for errors and is re-sent if there is an error.

9


j)

k) l)

m) n)

o)

p)

q) r) s)

t)

Anyone who has used the Internet has noticed that at times the information travels at different speeds. Depending on the amount of information that is being transferred, the information will arrive at it's destination at different times. The amount of information that can travel through a line is limited. This limit is called bandwidth. There are many more variables involved in communication technology using computers, much of which is covered in the section on the Internet. Scanners- Scanners allow you to transfer pictures and photographs to your computer. A scanner 'scans' the image from the top to the bottom, one line at a time and transfers it to the computer as a series of bits or a bitmap. You can then take that image and use it in a paint program, send it out as a fax or print it. With optional Optical Character Recognition (OCR) software you can convert printed documents such as newspaper articles to text that can be used in your word processor. Most scanners use TWAIN software that makes the scanner accessable by other software applications. Digital cameras allow you to take digital photographs. The images are stored on a memory chip or disk that can be transferred to your computer. Some cameras can also capture sound and video. Case - The case houses the microchips and circuitry that run the computer. Desktop models usually sit under the monitor and tower models beside. They come in many sizes, including desktop, mini, midi, and full tower. There is usually room inside to expand or add components at a later time. By removing the cover off the case you may find plate covered, empty slots that allow you to add cards. There are various types of slots including IDE, ASI, USB, PCI and Firewire slots. Depending on the type notebook computers may have room to expand . Most Notebooks also have connections or ports that allows expansion or connection to exterior, peripheral devices such as monitor, portable hard-drives or other devices. Cards - Cards are components added to computers to increase their capability. When adding a peripheral device make sure that your computer has a slot of the type needed by the device. Sound cards allow computers to produce sound like music and voice. The older sound cards were 8 bit then 16 bit then 32 bit. Though the human ear can't distinguish the fine difference between sounds produced by the more powerful sound card they allow for more complex music and music production. Colour cards allow computers to produce colour (with a colour monitor of course). The first colour cards were 2 bit which produced 4 colours [CGA]. It was amazing what could be done with those 4 colours. Next came 4 bit allowing for 16 [EGA and VGA ] colours. Then came 16 bit allowing for 1064 colours and then 24 bit which allows for almost 17 million colours and now 32 bit and higher allow monitors to display almost a billion separate colours. Video cards allow computers to display video and animation. Some video cards allow computers to display television as well as capture frames from video. A video card with a digital video camera allows computers users to produce live video. A high speed connection is required for effective video transmission. Network cards allow computers to connect together to communicate with each other. Network cards have connections for cable, thin wire or wireless networks. For more information see the section on Networks. Cables connect internal components to the Motherboard, which is a board with series of electronic path ways and connections allowing the CPU to communicate with the other components of the computer. Memory - Memory can be very confusing but is usually one of the easiest pieces of hardware to add to your computer. It is common to confuse chip memory with disk storage. An example of the difference between memory and storage would be the difference between a table where the actual work is done (memory) and a filing cabinet where the finished product is stored (disk). To add a bit more confusion, the computer's hard disk can be used as temporary memory when the program needs more than the chips can provide. Random Access Memory or RAM is the memory that the computer uses to temporarily store the information as it is being processed. The more information being processed the more RAM the computer needs. One of the first home computers used 64 kilobytes of RAM memory (Commodore 64). Today's modern computers need a minimum of 256 Mb (recommended 1 Gb or more) to run Windows or OS x with modern software. 10


RAM memory chips come in many different sizes and speeds and can usually be expanded. Older computers came with 512 Kb of memory which could be expanded to a maximum of 640 Kb. In most modern computers the memory can be expanded by adding or replacing the memory chips depending on the processor you have and the type of memory your computer uses. Memory chips range in size from 1 Mb to 32 GB and more. As computer technology changes the type of memory changes as well making old memory chips obsolete. Check your computer manual to find out what kind of memory your computer uses before purchasing new memory chips. 2. What is Computer Software? The software is the information that the computer uses to get the job done. Software needs to be accessed before it can be used. There are many terms used for the process of accessing software including running, executing, starting up, opening, and others. Computer programs allow users to complete tasks. A program can also be referred to as an application and the two words are used interchangeably. Examples of software programs or applications would be the Operating Systems such as DOS, Windows, UNIX, Mac OS and various others, Word processors (typing letters), Spreadsheets (financial info), Databases (inventory control and address book), Graphic Programs, Internet Browsers, Emails and many others. As well any document that you create, graphic you design, sound you compose, file you make, letter you write, email you send or anything that you create on your computer is referred to as software. All software is stored in files. Software is stored on a disk, card, tape or one of the dozens of other storage devices available. There are millions of different pieces of software available for almost every conceivable need. Software is available commercially through stores and mail order and also available on the Internet. Software is also available through an Open Source license which allows anyone to use the Open Source software free of charge as long as the license is maintained. If you can't find the application that you need software development companies can custom designed software for you. The largest software companies offer packages of software or suites that include many of the programs that the average person or business needs. Software packages or suites contain programs that work together and share information, making it easier to combine that information in versatile ways. For example when writing a letter you can get the mailing address from an address book, include a letterhead from a graphics program and include a financial chart from a spreadsheet and combine this collection of information in the body of the letter. The three basic types of software are; commercial, shareware and open source software. Some software is also released into the public domain without a license. Commercial software comes prepackaged and is available from software stores and through the Internet. Shareware is software developed by individual and small companies that cannot afford to market their software worldwide or by a company that wants to release a demonstration version of their commercial product. You will have an evaluation period in which you can decide whether to purchase the product or not. Shareware software often is disabled in some way and has a notice attached to explain the legal requirements for using the product. Open Source software is created by generous programmers and released into the public domain for public use. There is usually a copyright notice that must remain with the software product. Open Source software is not public domain in that the company or individual that develops the software retains ownership of the program but the software can be used freely. Many popular Open Source applications are being developed and upgraded regularly by individuals and companies that believe in the Open Source concept. 2-1 System Software 11


System software is a catch-all term for the programs that handle the running of your computer's hardware. The two main categories are: -

Operating System such as Windows XP, Windows 2008 server, Vista, Seven, Linux Red hat, Unix, Mac OS Lion, Mac OS Mountain etc. Utility Programs include WinZip, WinRAR, Antivirus, Uninstallers, Drivers etc.

2-1-1 Operating System Operating Systems between the hardware and the application software lies the operating system. The operating system is a program that conducts the communication between the various pieces of hardware like the video card, sound card, printer, the motherboard and the applications. What can a computer do without an operating system? Not much!! Let's look at what happens when you turn on your computer, before the operating system is involved. The first screen you see when you turn your computer on will be about the BIOS (Basic Input/output System) of your computer. The BIOS is a set of instructions on a ROM chip (Read-Only Memory) that controls how the hardware and the operating system communicate. It's a very limited set of instructions. Notice the instruction to "Hit DEL if you want to run Setup." Other keys might be used for a different brand of BIOS. Don't do this unless you know what you are trying to do. Setup allows you change certain features of your computer at a very basic level, but doing it wrong can keep it from working right or even at all! Older BIOS might not understand your newest, spiffiest piece of hardware. In this case you would have to get a new motherboard or updated BIOS. A newer motherboard will have BIOS that can be updated using software. It may require making a physical change on the inside of your computer, running a special software program, then resetting the motherboard back the way it was. (This is a task only for the brave and technically skilled since you can ruin a motherboard very easily!) After the BIOS have gone through its morning wake-up routine, you'll see on your screen something about running the POST (Power on Self-Test). This is a set of tests of the hardware. If, for example, your keyboard is not plugged in or is broken, you will see a message about "Keyboard failure" and the computer will stop where it is in the POST. There are tests included for the hard drives, memory, and the buses, too. This is only a quick check-up though and does not guarantee that everything is perfect. That's it for what the computer can do without an operating system. It can wake up and twitch a little, but it can't move or talk yet. Its nervous system is not working. Next the computer looks for some kind of operating system. It will usually be set up to look in the floppy drive first and then on the hard drive. This way if your hard drive fails, you have a way to get the system working enough to diagnose the problem. Enough of the operating system to get started will fit on a 3½" floppy disk. This part of the operating system has various names. Kernel, master program, supervisor, control program are a few. In PCs using DOS or Windows the term kernel is used. When the kernel is loaded, the computer looks for three files: Command language interpreter: The command language interpreter is the program that turns your keystrokes into all those 1's and 0's for the processor to swallow. For DOS and Windows 95 the program is command.com. Config.sys: From the config.sys the computer finds what devices are connected, such as a mouse, CD drive, or scanner. The file tells where to look for the directions, called drivers, for using these devices. Here is an example of a config.sys that might be used with Windows 95, with explanations in blue on the right. The blue parts can't be in the real file. Win95 doesn't require a config.sys unless there are devices that you want to run in DOS mode.

12


Autoexec.Bat: This file does optional tasks like loading programs that you want to start every time your computer is turned on. You may see a lot of messages on the screen as the various programs are started. This file also tells the computer where to look for files, called the path. Many programs add their own directories to the path when they are installed. The path can get too long to function right! Here's an example of an autoexec.bat that might be used under Windows 95, with explanations on the right in blue. The blue parts can't be in the real file. Win95 doesn't require an autoexec.bat but you might want to change some of the defaults or to have some things to run in DOS mode.

2-1-2 Functions of the OS All operating systems must handle the same basic tasks. These functions can be divided into three groups:

A- Allocating System Resources: The operating system directs the traffic inside the computer, deciding what resources will be used and for how long. Time in the CPU is divided into time slices which are measured in milliseconds. Each task the CPU does is assigned a certain number of time slices. When time expires, another task gets a turn. The first task must wait until it has another turn. Since time slices are so small, you usually can't tell that any sharing is going on. Tasks can be assigned priorities so that high priority (foreground) tasks get more time slices than low priority (background) tasks.

A-1. Memory: Memory must be managed also by the operating system. All those rotating turns of CPU use leave data waiting around in buffers. Care must be taken not to lose data!! One way to help out the traffic jam is to use virtual memory. This includes disk space as part of main memory. While it is slower to put data on a hard disk, it increases the amount of data that can be held in memory at one time. When the memory chips get full, some of the data is paged out to the hard disk. This is called swapping. Windows uses a swap file for this purpose.

A-2. Input and output Flow control is also part of the operating system's responsibilities. The operating system must manage all requests to read data from disks or tape and all writes to these and to printers. To speed up the output to printers, most operating systems now allow for print spooling, where the data to be printed is first put in a file. This frees up the processor for other work in between the 13


times data is going to the printer. A printer can only handle so much data at a time. Without print spooling you'd have to wait for a print job to finish before you can do anything else. With it you can request several print jobs and go on Working. The print spool will hold all the orders and process them in turn. B- Monitoring System Activities B-1 System performance: A user or administrator can check to see whether the computer or network is getting overloaded. Changes could be made to the way tasks are allocated or maybe a shopping trip is in order! System performance would include response time (how long it takes for the computer to respond when data is entered) and CPU utilization (comparing the time the CPU is working to the time it is idle.) B-2 System Security: Some system security is part of the operating system, though additional software can add more security functions. For multiple users who are not all allowed access to everything, there must be a logon or login procedure where the user supplies a user name or ID and a secret password. An administrator must set up the permissions list of who can have access to what programs and what data. C- File and Disk Management Keeping track of what files are where is a major job. If you can't find a file, it doesn't help to know that it is safe and secure somewhere. So an operating system comes with basic file management commands. A user needs to be able to create directories for storing files. (Dumping everything in one pile soon becomes the needle-in-the-haystack story.) A user needs to copy, move, delete, and rename files. This is the category of operating system functions that the user actually sees the most. A more technical task is that of disk management. Under some operating systems your hard disk can be divided up, or partitioned into several virtual disks. The operating system treats each virtual disk as though it were a physically separate disk. Managing several physical and/or virtual disks can get pretty complex, especially if some of the disks are set up with different operating systems. (Some folks are never satisfied with just one of anything!) 2-1-3 Types of System Software There are two basic types of operating systems: Single program: A single program operating system allows only one program to run at a time. This means that if you are working in a spreadsheet and want to write a memo, you must shut down the spreadsheet application and open up a word processor. This is annoying, especially if you need to quote some data from the spreadsheet in your memo! So new operating systems were designed that allowed multiple programs to run at the same time. Multitasking: The simplest form is multi-tasking. What this really means is that the programs are taking turns with the processor. It allows a single user to have the spreadsheet and the word processor open at the same time, and even more. Now the user can see to copy data from one to the other. Much better!! The computer must decide on how many time slices each program gets. The active program gets the most. Next is a program that are doing things but which aren't the foreground program. Last is programs that are open but aren't doing anything. They need a little bit of time every now and then to see if they are supposed to do something yet. The next step up in complexity is multiple users. On a network several users can be using the same computer or even the same program on that computer. This is called time-sharing. If a computer has multiple CPUs, it can do multiprocessing. Rather than a single CPU giving out turns to various programs, the different CPUs can work simultaneously. Speed increases immensely. Of course cost does, too! It is possible for a computer to use more than one operating system through the use of virtual machines. “Virtual� means it's not really there. But programs written for different operating systems are fooled into thinking their required operating system is present. 14


2-1-4 Common Operating Systems for Desktop Computers Originally the operating system was created by each company that manufactured a processor and motherboard. So each operating system was proprietary, that is, unique to each manufacturer. Problem: changing to a new computer meant your software had to be replaced! Not good marketing. So there was pressure early on to standardize things so that software could be transferred to the new (and of course better!) computer. This required more standardization in operating systems. The winner in the PC market was MS-DOS, Microsoft's Disk Operating System, and its twin at IBM, PC-DOS, also written by Microsoft. Now it's hard to recall those days when each computer had its own unique operating system. 2-1-5 Common DOS (Disk Operating System) Commands: CD: Change directory, when you want to move from one directory to another e.g cd c: will take you the the root directory c. Dir: show directory e.g c:\users>dir Help: shows all the command available in dos to use e.g c:\users>help Format: very dangerous command , it permits the user to erase all information found on the specified drive e.g c:FORMAT C: SCANDISK/CHKDSK: Use to verify the integrity and repair errors found on the drive. Very essential especially when your computer suddenly goes off. C:\chkdsk MKDIR: Helps to create a new directory e.g . C:\mkdir barr COPY: Helps to copy files from folders to folder or drive to drive DEL: deletes one or more files For more DOS commands you just need to type c:\help on your command prompt and you will get advice on how to use these commands and more . Windows versions : They include (95, 98, Me, NT, 2000, XP, Vista, and 7) are operating systems on their own. The earlier versions of Windows use DOS as the operating system and add a graphical user interface which will do multitasking. But with Windows 95 Microsoft released an operating system that can take advantage of the 32-bit processors. Apple Macintosh: is a multitasking operating system that was the first graphical interface to achieve Commercial success. The Mac was an immediate success in the areas of graphics production, and still commands the lion's share of that market. Apple made a major marketing error when they decided to keep their hardware and software under tight control rather than licensing others to produce compatible devices and programs. While the Apple products were of high quality, they were always more expensive than comparable products that were compatible with Microsoft's DOS operating system. The current version is Mac OS X, which is version 10. Since January 2002, all new Mac computers use Mac OS X. Subversions are named Jaguar, Panther, Tiger, Leopard, Lion and recently Lion Mountain. UNIX: is an operating system developed by Bell Labs to handle complex scientific applications. University Networks are likely to use UNIX, as are Internet Service Providers. A lot of people have experience with UNIX from their college work. Many computer old-timers love UNIX and its command line interface. But all those commands are not easy to remember for newcomers. X-Windows is a graphical interface for UNIX that some think is even easier to work with than Windows 98. Linux: is an operating system similar to UNIX that is becoming more and more popular. (And it has the cutest logo!) It is an open-source program created by Linus Torvalds at the University of Finland, starting in 1991. Open source means that the underlying computer code is freely available to everyone. Programmers can work directly with the code and add features. They can sell their customized version of Linux, as long as the source code is still open to others. 2-2 Utilities Software A utility program performs tasks related to the maintaining of your computer's health - Hardware or data. Some are included with the operating system. But someone always thinks they have a better version for you to buy. And they are frequently right! 15


They include: i) File Management programs: make it easier to manage your files. In the high days of DOS it didn't take much to improve on the text-only type-it-all-yourself methods that DOS provided. Many programs were written to help the user find files, create and organize directories, copy, move, and rename files. Some even used the mouse to point and click to accomplish these tasks. You don't appreciate the vastness of the improvement until you've tried to do these things by typing the commands. The newer graphical interfaces that come with current operating systems have reduced the need for alternate file management programs. ii) Disk Management programs: involve formatting and defragmenting disks. Defragmenting means putting files on the disk so that the whole file is in sequence. This reduces the time to access the file. Some disk management programs even let you specify that certain files that are accessed often, like the operating system itself and frequently used programs, are at the front of the disk. Anything that speeds things up will have customers. iii) Memory Management software: handles where programs put their current data in RAM. They move certain memory-resident items out of the way. This can effectively increase the memory available by getting all the unused pieces together in one spot, making a useable amount. iv) Backup program, which also restores the backed up data, is a must if you have any data at all that you want to keep around for a while. The software will compress the data to take up the least space v) Data Recovery programs are for those who just said "Whoops!" They attempt to recover deleted or damaged (corrupted) files. Use immediately or forget about it! vi) Data Compression programs squeeze out the slack space generated by the formatting schemes such as WinZip and WinRAR. vii) Security Software: This category includes a number of different kinds of programs, all of which are trying to protect your computer and your data from attacks and damage and being controlled without permission. No one program can protect against all of the bad guys out there. Using a set of overlapping programs is the best way to keep your computer and its data safe. Malware is what we call the whole category of things that try to do bad things to your computer or your data. Malware: What you need protection from  Viruses copy themselves to other disks to spread to other computers. They can be merely annoying or they can be vastly destructive to your files.  Trojans hide inside something else to sneak in unwanted programs. You don't know that they are there, like the famous Trojan horse. These are often used to capture your logins and passwords.  Worms are unwanted programs that are transferred over network or Internet connections to spread themselves quickly.  Spyware programs lurk on your computer to steal important information, like your passwords and logons and other personal identification information and then send it off to someone else.  Zombie programs take control of your computer and use it and its Internet connection to attack other computers or networks or to perform criminal activities.  Phishing (pronounced like the word 'fishing') is a message that tries to trick you into providing information like your social security number or bank account information or logon and password for a web site. The message may claim that if you do not click on the link in the message and log onto a financial web site that your account will be blocked, or some such disaster.  Spam is email that you did not request and do not want. One person's spam is another's useful newsletter or sale ad. Spam is a common way to spread viruses, trojans, and the like.  Browser hijacking occurs when one of the nasties takes control of your browser, sending you to sites that you did not mean to go to. This may be a porn site or it may look like a real banking, sales, or credit card site. The purpose is to steal your personal and financial information.  Anti-virus programs monitor the computer for the activity of viruses and similar nasties. 16


 Anti-spyware programs similarly monitor your computer, looking for known trouble-makers as well as suspicious behavior.  Anti-spam software tries to identify useless or dangerous messages for you.  A firewall blocks attempts to access your files over a network or internet connection. Your network router or modem or both may have a hardware firewall built into it. That will block incoming attacks. But you still need a software firewall on your computer to block outgoing attacks. Your computer can become infected through shared disks or even from another computer on the network. So you need to monitor what your computer is putting out over the network or internet also. QUESTIONS AND ANSWERS 1. Name 3 things the operating system does? Answer: - Manages the disks and files - Manages the computer's resources - Manages the computer's memory 2. A proprietary operating system is? Answer: Unique to a Manufacturer. 3. Name what function of a computer BIOS? Answer: Check for the presence of peripherals like mouse, sound card, and scanner 4. Windows versions before Windows 95 where? Answer: Are proprietary operating systems and the first successful graphical operating systems 5. What is a Backup Program? Answer: A backup program is a program that copies and stores selected files for recovery purposes. 6. What harm can a computer virus cause to your computer? Answer: i) Can Damage your files including system files. ii) Can damage hardware such as hard drives. iii) Can damage your computer software programs. 7) Define an Operating System?

17


CHAPTER 3 3- INPUT, PROCESSING, OUTPUT AND STORAGE

In this chapter we are going to study the various components of computer, by categorizing them into sub groups and also by relating them to overall success of a computer system. 3-1 Input What is input? Basically, everything we tell the computer is input . Before we move further into the topic , its good that we revise some basic concepts that I thought we might have forgotten ; i) Data means the raw facts given to the computer. ii) Programs are the sets of instructions that direct the computer. iii) Commands are special codes or key words that the user inputs to perform a task, like RUN "ACCOUNTS". These can be selected from a menu of commands like "Open" on the File menu. They may also be chosen by clicking on a command button. Iv) User response is the user's answer to the computer's question, such as choosing OK, YES, or NO or by typing in text, for example the name of a file. 3-1-1 Types Of Input Keyboard: The first input device we will look at is the Keyboard. The image used on the next page to illustrate the various keys may not look like the keyboard you are using. Several variations are popular and special designs are used in some companies. The keyboards shown below put the function keys in different places. The Enter and Backspace keys are different shapes and sizes. One has arrow keys while the other doesn't. It's enough to confuse a person's fingers!!

The backslash key has at least 3 popular placements: at the end of the numbers row, above the Enter key, and beside the Enter key. We also have the Windows keyboards which have two extra keys. One pops up the Start Menu and the other displays the right-click context sensitive menu. Ergonomic keyboards even have a different shape, curved to fit the natural fall of the wrists. Mouse: A ball underneath rolls as the mouse moves across the motion of the mouse. Buttons on the mouse can be clicked or doubleclicked to perform tasks, like to select an icon on the screen or to open the selected document. Many recent mice have a scroll wheel as the middle button. There are new mice that don't have a ball at all. They use a laser to sense the motion of the mouse instead. Advantage: Moves cursor around the screen faster than using keystrokes. Disadvantage: Requires moving hand from keyboard to mouse and back. Repeated motion can lead to carpal tunnel syndrome

18


Trackball :Instead of moving the whole mouse around, the user rolls the trackball only, which is on the top or side. Advantage: Does not need as much desk space as a mouse. Is not as tiring since less motion is needed. Disadvantage: Requires fine control of the ball with just one finger or thumb. Repeated motions of the same muscles is tiring and can cause carpal tunnel syndrome.

Glidepad :Uses a touch sensitive pad for controlling cursor. The user slides finger across the pad and the cursor follows the finger movement. For clicking there are buttons, or you can tap on the pad with a finger. The glidepad is a popular alternate pointing device for laptops. Advantage: Does not need as much desk space as a mouse. Can readily be built into the keyboard. Has finer resolution. That is, to achieve the same cursor movement onscreen takes less movement of the finger on the glidepad than it does mouse movement. Can use either buttons or taps of the pad for clicking. Disadvantage: The hand tires faster than with a mouse since there is no support. Some people don't find the motion as natural as a mouse. Game Devices :Cursor motion controlled by vertical stick (joystick) or arrow buttons (gamepad) Advantage: A joystick gives a more natural-feeling control for motion in games, especially those where you are flying a plane or spaceship. Both have more buttons for special functions than a mouse and can combine buttons for even more actions. Disadvantage: More expensive Bulky Better ones require an additional peripheral card for best performance.

Pen Input Used esp. in Personal Digital Assistants (PDA) Also called a stylus. Pen Input is used for: Data Input - by writing. PDA recognizes your handwriting. (If only your friends could, too!) Pointing Device - Functions like a mouse in moving a cursor around the screen and clicking by tapping the screen. Command Gestures - You can issue commands by moving pen in patterns. So a certain kind of swirl would mean to save the file and a different kind of swirl could mean to open a new file.

Advantage: Can use handwriting instead of typing Can use gestures instead of typing commands Small size Disadvantage: Must train device to recognize handwriting. Must learn gestures or train device to recognize the ones you create Can lose the pen which is not usually attached to the device Touchscreen Make selection by just touching the screen. Advantage: It's natural to do - reach out and touch something. Disadvantage: It's tiring if many choices must be made. It takes a lot of screen space for each choice since fingers are bigger than cursors. Digitizers and Graphics Tablets 19


Converts drawings, photos, etc. to digital signal. The tablets have special commands Advantage: Don't have to redraw graphics already created Most find it easier to draw with a stylus than with a mouse. Disadvantage: Expensive A terminal consists of a keyboard and a screen so it can be considered an input device, especially some of the specialized types. Some come as single units. Terminals are also called: - Display Terminals - Video Display Terminals or VDT A dumb terminal has no ability to process or store data. It is linked to minicomputer, mainframe, or super computer. The keyboard and viewing screen may be a single piece of equipment. An intelligent, smart, or programmable terminal can process or store on its own, at least to a limited extent. PCs can be used as smart terminals. A point-of-sale terminal (POS) is an example of a special purpose terminal. These have replaced the old cash registers in nearly all retail stores. They can update inventory while calculating the sale. They often have special purpose keys. For example, many restaurants have separate touchpads for each food item available. Credit card readers, fingerprint scanners, and the like are special purpose devices that send data to a computer for recognition. Multimedia is a combination of sound and images with text and graphics. This would include movies, animations, music, people talking, sound effects like the roar of a crowd and smashing glass. So when talking about input devices, we should include multimedia because the process for which sound is captured into the computer for processing is via an input device. The following are sound input devices; Microphones, Pianos, Drums, and Guitars: Recording sounds for your computer requires special equipment. Microphones can capture sounds from the air which is good for sound effects or voices. For music the best results come from using a musical instrument that is connected directly to the computer. Software can combine music recorded at different times. You could be a music group all by yourself - singing and playing all the parts! Data entry - Talking data into the computer when your hands and eyes are busy should certainly be more efficient. You'd have to be very careful about your pronunciation! Command and control - Telling the computer what to do instead of typing commands, like saying "Save file". Be careful here, too. The dictionary of understood words does not include some of the more "forceful" ones. Speaker recognition - Security measures can require you to speak a special phrase. The computer must recognize your voice to let you in. Speech to text - Translating spoken words direct to type would suit some authors just fine. You'd have to watch out for those "difficult to translate" phrases like "hmmm" and "ah, well, ... ummm." How do they change voice to data?? 1. Convert voice sound waves to digital form (digital signal processing -DSP) 2. Compare digitized voice input to stored templates 3. Check grammar rules to figure out words 4. Present unrecognized words for user to identify Video Input A digital camera takes still photos but records the pictures on computer disks or memory chips. The information contained can be uploaded to a computer for viewing. 20


A video camera or recorder (VCR) can record data that can be uploaded to the computer with the right hardware. Though it is not digital data, you can still get good results with the right software. Both of these take huge amounts of storage. Photos make for very large files. A web cam is a tiny video camera designed especially to sit on your computer. It feeds pictures directly to the computer - no tape or film to develop. Of course you are limited by the length of the cable that connects the camera to the computer. But like any camera, it will take a picture of what you point it at! So what do people do with a web cam? They use it for video conferencing over the Internet or Skype video phone calls. They show the world what's going on outside their window (weather, traffic). They take digital pictures and make moviesfamily, pets, snow storms, birthday parties, whatever. General Devices ScannerThe scanner works like a copy machine. It creates a digital image of what it scanned. Scanned text cannot be edited at this point. Flatbed scanners open wide enough to allow you to lay a document or book flat on the glass surface. You can even make a scan of your hand! A document scanner can only scan individual sheets of paper, not books or objects. Bar-Code Scanner Hand-held or fixed devices that can read the bar codes on packages. Credit Card Reader Swipe the credit card through the device, which reads the magnetic numbers in the magnetic strip on the card. 3-2 PROCESSING 3-2-1 what is processing? Processing is the thinking that the computer does - the calculations, comparisons, and decisions. People also process data. What you see and hear and touch and feel is input. Then you connect this new input with what you already know, look for how it all fits together, and come up with a reaction, your output. "That stove is hot. I'll move my hand now!" The kind of "thinking" that computers do is very different from what people do. Machines have to think the hard way. They do one thing at a time, one step at a time. Complex procedures must be broken down into VERY simple steps. Then these steps can be repeated hundreds or thousands or millions of times. All possible choices can be tried and a list kept of what worked and what didn't. People, on the other hand, are better at recognizing patterns than they are at single facts and step-by-step procedures. For example, faces are very complex structures. But you can identify hundreds and even thousands of different faces with just a glance. A human can easily tell one face from another, even when the faces belong to strangers. You don't recognize Mom's face because you remember that Mom's nose is 4 cm long, 2.5 cm wide, and has a freckle on the left side! You recognize the whole pattern of Mom's face. There are probably a lot of folks with noses the size and shape of Mom's. But no one has her whole face. But a computer must have a lot of specific facts about a face to recognize it. Teaching computers to pick Mom's face out of a crowd is one of the hardest things scientists have tried to do yet with computers. But babies do it naturally! So computers can't think in the same way that people do. But what they do, they do excellently well and very, very fast. 3-2-2 Digital Data Modern computers are digital that is; all info is stored as a string of zeros or ones - off or on. All the thinking in the computer is done by manipulating these digits. The concept is simple, but working it all out gets complicated. 1 bit = one on or off position 1 byte = 8 bits So 1 byte can be one of 256 possible combinations of 0 and 1. Numbers written with just 0 and 1 are called binary numbers. Each 1 is a power of 2 so that the digits in the figure represent the number: = 27 + 0 + 2 5 + 0 + 2 3 + 22 + 0 +0 = 128 +0 +32 + 0 + 8 + 4 + 0 + 0 21


= 172 Every command and every input is converted into digital data, a string of 0's and 1's. 3-2-3 Digital Codes All letters, numbers, and symbols are assigned code values of 1's and 0's. A number of different digital coding schemes are used by digital devices. Three common code sets are: ASCII (used in UNIX and DOS/Windows-based computers) EBCDIC (for IBM System 390 main frames) Unicode (for Windows NT and recent browsers) The ASCII code set uses 7 bits per character, allowing 128 different characters. This is enough for the English alphabet in upper case and lower case, the symbols on a regular English typewriter, and some combinations reserved for internal use. An extended ASCII code set uses 8 bits per character, which adds another 128 possible characters. This larger code set allows for foreign languages symbols like letters with accents and several graphical symbols. ASCII has been superseded by other coding schemes in modern computing. But it is still used for transferring plain text data between different programs or computers that use different coding schemes Unicode uses 16 bits per character, so it takes twice the storage space that ASCII coding, for example, would take for the same characters. But Unicode can handle many more characters. The goal of Unicode is to represent every element used in every script for writing every language on the planet. 3-2-3 Parity With all these 0's and 1's, it would be easy for the computer to make a mistake! Parity is a clever way to check for errors that might occur during processing. In an even parity system an extra bit (making a total of 9 bits) is assigned to be on or off so as to make the number of on bits even. So in our example above 10101100 there are 4 on bits (the four 1's). So the 9th bit, the parity bit, will be 0 since we already have an even number of on bits. In an odd parity system the number of on bits would have to be odd. For our example number 10101100, there are 4 on bits (the 1's), so the parity bit is set to on, that is 1, to make a total of 5 on bits, an odd number. If the number of on bits is wrong, an error has occurred. You won't know which digit or digits are wrong, but the computer will at least know that a mistake occurred. Memory chips that store your data can be parity chips or non-parity chips. Mixing them together can cause odd failures that are hard to track down. 3-3 CPU (CENTRAL PROCESSING UNIT) The CPU, or Central Processing Unit, is the part of the computer where work gets done. In most computers, there is one processing chip. It generally referred to as the heart of the computer because all instructions are performed at this level. It comprises of a memory unit, a control Unit CU and an Arithmetic and Logic Unit generally referred to as the ALU Main Memory: Main Memory stores the commands that the CPU executes and the results. ALU: stands for Arithmetic/Logic Unit This is the part that executes the computer's commands. A command must be either a basic arithmetic operation: + - * / or one of the logical comparisons: > < = not =. Everything else has to be broken down into these few operations. Only one operation is done in each Machine Cycle. The ALU can only do one thing at a time but can work very, very fast.

Applications These are the various programs that are currently running on the computer. 22


By taking turns with the Machine Cycle, modern computers can have several different programs running at once. This is called multi-tasking. Each open application has to have some data stored in Main Memory, even if the application is on rest break and is just sitting there. Some programs (graphics programs are notorious for this) require a lot of the Main Memory space, and may not give it up even if they are shut down! Rather rude, actually!! Control Unit This is the part of the computer that controls the Machine Cycle. It takes numerous cycles to do even a simple addition of two numbers.

CPU: Stands for Central Processing Unit .This is the part of the computer that does the "thinking." Input/output Storage: When you enter new data, the keystrokes must be stored until the computer can do something with the new data. When you want data printed out or displayed, it must be stored somewhere handy first. Main Memory (Primary Memory): This is where the computer stores the data and commands that are currently being used. When the computer is turned off, all data in Main Memory vanishes. A data storage method of this type is called volatile since the data "evaporates." Operating System: This is the instructions that the computer uses to tell itself how it "operates". It's the answer to "Who am I and what can I do?" Some common operating systems are DOS, various versions of Windows, OS/2, UNIX, LINUX, System 7. These all behave in very different ways and have different hardware requirements. So they won't all run on all machines. Only the parts of the operating system that are currently being used will be loaded into Main Memory. Unused Storage :One hopes that there is always some storage space that is not in use. If space runs out in Main Memory, the computer will crash, that is, stop working. There are programs that sense when space is getting short and warn the user. The user could then close some of the open applications to free up more space in Main Memory. Sometimes the warning is too late to prevent the crash. Remember that all the data in Main Memory vanishes when the power goes off. Thus a crash can mean a lot of lost work. Working Storage :The numbers and characters that are the intermediate results of computer operations must be stored until the final values are calculated. These values "in progress" are kept in temporary locations. For example, if the computer is adding up the numbers 3, 5, and 6, it would first add 3 to 5 which yields a value of 8. The 8 is stored in working storage. Then the 8 and 6 are added and the new value 14 is stored. The value of 14 is now available to be displayed on the screen or to be printed or to be used in another calculation. Machine Cycle:The computer can only do one thing at a time. Each action must be broken down into the most basic steps. One round of steps from getting an instruction back to getting the next instruction is called the Machine Cycle. The Machine Cycle - Fetch - get an instruction from Main Memory - Decode - translate it into computer commands - Execute - actually process the command - Store - write the result to Main Memory

23


For example, to add the numbers 5 and 6 and show the answer on the screen requires the following steps: 1. Fetch instruction: "Get number at address 123456" 2. Decode instruction. 3. Execute: ALU finds the number. (which happens to be 5) 4. Store: The number 5 is stored in a temporary spot in Main Memory. 5 - 8 Repeat steps for another number (= 6) 9. Fetch instruction: "Add those two numbers" 10. Decode instruction. 11. Execute: ALU adds the numbers. 12. Store: The answer is stored in a temporary spot. 13. Fetch instruction: "Display answer on screen." 14. Decode instruction. 15. Execute: Display answer on screen.

Speed :The immense speed of the computer enables it to do millions of such steps in a second. In fact, MIPS, standing for millions of instructions per second, is one way to measure computer speeds. Memory Addresses:We need a method of naming the places where Main Memory stores data. Each location needs a unique name, just like houses in a town need a unique street address.

Rather than a street name and house number, memory addresses are just numbers. A memory address holds 1 byte of data where 1 bit = 0 or 1, on or off 1 byte = 8 bits 1 kilobyte (K or KB) = 1024 bytes 1 megabyte (MB) = 1024 kilobytes You might wonder why 1024 instead of 1000 bytes per kilobyte. That is because computers don't count by tens like people. Computers count by twos and powers of 2. 1024 is 2 x 2 x 2 x 2 x 2 x 2 x 2 x 2 x 2 x 2, that is 2 times itself ten times. It's a rather convenient size number (for computers!). Update: Things are changing faster than I can type! The explanation above is no longer entirely true (July 2000). Different scientific and technical areas are using the words differently. For data storage devices and telecommunications a megabyte is 1 000 000 bytes. For data transmission in LANs a megabyte is 1 048 576 bytes as described above. But for data storage on a floppy disk a megabyte is 1 024 000 bytes! Processor Speed:We all are impatient and want our computer to work as fast as possible, and certainly faster than the guy's at the next desk! Many different factors determine how fast your computer gets things done. Processor speed is one factor. But what determines the processor's speed? Processor Speed affected by: 1) System clock rate = rate of an electronic pulse used to synchronize processing (Only one action can take place between pulses.) Measured in megahertz (MHz) where 1 MHz = 1 million cycles per second or gigahertz (GHz) where 1 GHz = 1 billion cycles per second. This is what they are talking about if they say a computer is a 24


2.4 GHz machine. It's clock rate is 2.4 billion cycles per second. Bigger number = faster processing Bus width = the amount of data the CPU can transmit at a time to main memory and to input and output devices. (Any path bits travel is a bus.) An 8-bit bus moves 8 bits of data at a time. Bus width can be 8, 16, 32, 64, or 128 so far. Think of it as "How many passengers (bits) can fit on the bus at once to go from one part of the computer to another." Bigger number = faster transfer of data Word size = a word is the amount of data the CPU can process at one time. An 8-bit processor can manipulate 8 bits at a time. Processors can be 8-, 16-, 32-, or 64-bit so far. Bigger the number = faster processing Physical Components There are several physical components of a computer that are directly involved in processing. The processor chip itself, the memory devices, and the motherboard are the main ones. Microprocessor- a single silicon chip containing CPU, ALU, and some memory. The ROM (Read Only Memory) contains the minimum instructions that the computer needs to get started, called booting. What a user does on the computer cannot change what is stored in ROM. There may also be another chip dedicated to calculations. The microprocessor chip is located on a large circuit board called the main board or motherboard. The physical size of a computer chip is very small, as the ant below illustrates. Processor speed is measured in Megahertz (MHz) or Gigahertz (GHz). Memory Devices: Vacuum tube - oldest type. Didn't hold up long and generated a lot of heat. Core - small metal rings. Magnets tip a ring to left or right, which represents on and off. Relatively slow. Semiconductor - integrated circuit on a chip. This is what modern computers use for memory. Pictured below is a 72-pin SIMM.

Memory Speed RAM (Random Access Memory) is what the computer uses as Main Memory. Memory speed measures the time it takes to move data in or out of memory. It is measured differently for different kinds of memory chips: in nanoseconds (ns ) (smaller is faster) for EDO and FPM 1 ns = 1 billionth of a second. in megahertz (MHz) (higher is faster) for SDR SDRAM, DDR, SDRAM, and RDRAM. The capacity of a memory chip is measured in megabytes or gigabytes. For example, 256 MB of RAM is required to run Windows XP and 512MB is much better. For Windows 7 the requirements are 1 gigabyte (GB) RAM (32-bit) or 2 GB RAM (64-bit). Several such memory boards can be installed in the computer to increase the amount of RAM available. Motherboards have only so many slots for memory so there are limits. Some motherboards require that all slots be filled and that all slots contain the same size memory board. It can get frustrating as there are no warning labels about this! Motherboard:Here we see a diagram and a photo of a motherboard (or main circuit board). This one is suitable for a Pentium CPU. Nothing has been plugged in or attached yet.

25


Topic Questions 1. Define Processing and differentiate between electronic data processing with data processing? Ans: 2. Name the processes that an ideal information cycle has? Ans: Input ,Processing,Output and Storage 3. The Computer processor has how many parts? Ans:ALU,CU, and the Main Memory(Registers) 4. CPU stands for ? Ans: Central Processing Unit 5. What are the prime functions of the arithmetic/logic unit Ans: They do both calculation and Logical Comparison. 6. The name of the location of a particular piece of data is its Ans: Address 7. A megabyte is actually equal to ____ kilobytes. Ans: 1024 8. The clock rate of a processor is measured in Ans: megahertz or gigahertz 9. What is the use of a Computer Motherboard? Ans: Housed on the components such as the Processor, Memory, Chips and resistors etc. of the computer 10. Differentiate between a volatile and a nonvolatile Memory - losses information when there is no current for volatile memory while non-volatile memory such as the ROM(BIOS) does not loss information when there is no current . 4- Output What is An Output? Output is data that has been processed into useful form, now called Information. It can be viewed using a computer Monitor, or printed out using a printer. Types of Output -Hard copy: Printed on paper or other permanent media. -Soft copy: Displayed on screen or by other non-permanent means. Categories of Output - Text documents: including reports, letters, etc. - Graphics: including charts, graphs, pictures - Multimedia: which is a combination of text, graphics, video, audio The most often used means of Output are the printer for hard copy and the computer screen for soft copy. Let's look at the features of each. The job of a printer is to put on paper what you see on your monitor. How easy this is to do and how Successfully it is done determines whether or not you are happy with your printer. Monitor screens and printers do not use the same formatting rules. In the olden days of computers, 26


the way something looked on the screen could be VERY different from how it would look when printed. Early word processors didn't have a way to show what the printed version would look like. Now a word processor that doesn't have print preview, would be laughed off the shelf. Nowadays we expect to see a WYSIWYG view (What You See Is What You Get), where you see almost exactly what the document will look like in print, while you are still working on it. How fast? The speed of a printer is measured in: cps = characters per second lpm = lines per minute ppm = pages per minute The faster the printing, the more expensive the printer. What paper type used? Continuous-Form Paper: Advantage: Don't need to put in new paper often Disadvantage: May need to separate the pages and remove the strips of perforations from the edges. Single Sheet Advantage: Can change to special paper easily, like letterhead, card stock, or envelopes. Disadvantage: Must add paper more often What print quality? LQ Letter Quality = as good as best typewriter output NLQ Near Letter Quality = nearly as good as best typewriter output Draft used internally or for a test print The better the quality, the slower the printing. A more numerical measure of print quality is printer resolution. Measured in dots per inch (dpi), this determines how smooth a diagonal line is when printed. A resolution of 300 dpi will produce text that shows jagged edges only under a magnifying glass. A lower resolution than this will produce text with stair-step edges, especially at large sizes. Even higher resolutions are needed to get smooth photo reproduction. Professionals in graphics use 1200 to 2400 dpi printers. Draft quality on such a printer would be 600 dpi. What will it print? Printers vary in what varieties of type they can print. You must know the limits of your printer to avoid unhappy surprises! Modern printers can handle most anything, but older printers may not. Yes, there are still old, clunky computers and printers in use out there in the real world. Typeface Set of letters, numbers, and special characters with similar design Styles Bold, italic, underlined... Size Is measured in points One point = 1/72 of an inch like: 12 pt 18 pt 24 pt 36 pt Use 10 or 12 pt for writing a letter or report. Font A complete set of letters, etc. in the same typeface, style, and size Color Printing in color takes longer, uses more expensive inks/toner, looks best on more expensive papers, but can add a lot to the quality of the output Graphics Pictures add a lot to a document, but not all printers can print graphics. What kind of cable connection? 1. Serial cable: Sends data only 1 bit at a time Printer can be up to 1000 feet away from the computer. Maximum data transfer speed = 115 kilobits/s (.115Mbits/s)

27


2. Parallel cable: Sends data 8 bits at a time Printer must be within 50 feet of the computer. Maximum data transfer speed: 115 kilobytes/s (.115MBYTES/s). This is 8 times faster than the maximum serial speed. Newer printers may need bi-directional cable so that the printer can talk back to the computer. Such a cable is required if the printer can give helpful error messages. It's startling, but nice, the first time your computer politely says "Ink is getting low" or "Please place paper in the AutoSheet feeder." Oddly, Windows XP does not support spooling for a parallel connection to a printer. Spooling is what allows you to do other things on the computer while the printer is processing and printing the document. WinXP does spool when the printer uses a USB connection.

3. USB cable Printer must be within 5 meters (16.5 feet) of the computer, when connecting straight to the computer. [You can hook up several 5 m. cables and USB hubs in a chain - up to 25 meters.] Maximum data transfer speed: 12 megabits/s (1.5 MBYTES/s) Lots faster!

The new USB (Universal Serial Bus) connection is likely your best choice, if your printer can use it. It is faster and a USB connector can be unplugged and re-plugged without turning off the system. USB ports are rapidly replacing parallel ports. The printer cannot handle the data as fast as the USB port can send it. The real limit on how fast a printer works is in how fast printer can get the characters onto the paper. Serial cable may have to be used if a printer is shared in a fairly large office, due to the length of cable needed. Screen Features The device which displays computer output to us has various names: Screen: from "computer screen" or "display screen" Monitor: from its use as a way to "monitor" the progress of a program VDT = video display terminal from early network terminals CRT = cathode ray tube from the physical mechanism used for the screen. VDU = visual display unit to cover all the mechanisms from desktop CRTs to LCD flat screens on laptops to LED screen on palmtops. LCD screen: LCD (Liquid Crystal Display) screen is very flat and thin. LCD displays are made of two layers of a polarizing material with a liquid crystal solution in between, divided into tiny cells. An electrical signal to a cell makes the crystals line up in a way that keeps light from going through entirely or just partly. When the screen is black, all the crystals lined up so that no light gets through.

To make color an LCD screen uses 3 colored subcells for each cell: Red, Green, and Blue. This RGB system can create all the other colors by combining how much of each of these colors you see.The signal for a picture cleverly light ups just the right subcells in just the right strengths to show the desired color. Your eye blends the colors in the cells together and you see a picture. LCD screens used to be hard to see unless you were directly in front of the screen. Recent developments have fixed this issue. CRT screen:A CRT monitor screen uses a cathode ray tube. The screen is coated on the inside surface with dots of chemicals called phosphors. When a beam of electrons hits a dot, the dot will glow. 28


On a color monitor these phosphor dots are in groups of three: Red, Green, and Blue. This RGB system can create all the other colors by combining what dots are aglow. There are 3 signals that control the 3 electron beams in the monitor, one for each RGB color. Each beam only touches the dots that the signal tells it to light. All the glowing dots together make the picture that you see. The human eye blends the dots to "see" all the different colors. A shadow mask blocks the path of the beams in a way that lets each beam only light its assigned color dots. (Very cool trick!)

Screen Features Size : Desktop screens are usually 15 - 23 in. by diagonal measurement. (This is how TV screens are measured, too.) Larger sizes are available, at a significantly higher cost. Prices are dropping, however. Resolution: Determines how clear and detailed the image is. Pictures on a screen are made up of tiny dots. 1 dot on screen = 1 pixel (from "picture element") The more pixels per inch, the clearer and more detailed the picture. One measure of this is the dot pitch, the distance between the dots that make up the picture on the screen. However, different manufacturers measure differently. Most measure from dot center to the center of the nearest same color dot. Some measure from the center of a dot to an imaginary vertical line through the center of the nearest dot of the same color, giving a smaller number for the same dots as the previous method. Some monitors use skinny rectangles instead of dots and so must use a different method altogether. So, dot pitch has become less useful as a measure of monitor quality. A dot pitch of .28 is very common and .26 should be good for nearly all purposes, however it is measured. Refresh Rate: How often the picture is redrawn on the monitor. If the rate is low, the picture will appear to flicker. Flicker is not only annoying but also causes eye strain and nausea. So, a high refresh rate is desirable. 60 times per second is tolerable at low resolutions for most people. 75 times per second or more is better and is necessary for high resolutions. Type Old types = CGA, EGA, VGA Current type = super VGA Determines what resolutions are available and how many colors can be displayed. Type Stands for Resolution(s) CGA Color Graphics Adapter 320 x 200 EGA Extended Graphics Adapter 640 x 350 VGA Video Graphics Adapter 640 x 480 SVGA Super VGA 800 x 600, 1024 x 768, or 1280 x 1024 etc. New systems now come with super VGA with a picture size of 800 x 600 pixels (as a minimum) and 16 million colors . Color: The number of colors displayed can vary from 16 to 256 to 64 thousand to 16.7 million. The more colors, the smoother graphics appear, especially photos. The number of colors available actually depends more on the video card used and on how much memory is devoted to the display. It takes 8 bits to describe 1 pixel when using 256 colors. It takes 24 bits per pixel when using 16 million colors. So a LOT of memory is needed to get those millions of colors. Video cards now come with extra memory chips on them to help handle the load. Cursor/ Pointer :The symbol showing where you are working on the screen. In the olden days of just DOS, there were few choices for the cursor. The invention of the blinking cursor was a tremendous event. Under Windows there are a huge number of basic to fantasy cursors to choose from. Scrolling Moving the lines displayed on the screen up or down one line at a time Type of Screens -Monochrome one color text on single color background, i.e. white letters on blue, or green characters on black 29


-Color various colors can be displayed. (This one is easy!) -CRT Formerly most common type of monitor, which uses a cathode ray tube. -Liquid Crystal Display (LCD) Used in laptops esp. Large LCD monitors are the most common now. -Plasma Screens Used for very large screens and some laptops. Flat, good color, but much more expensive. Other Output devices include; Special tasks require special equipment. There are a number of special-use output devices. More are announced every day. From recording earthquake tremors to displaying CT scans, from recording analysis in a sound studio to displaying metal fatigue in aircraft structures, we have more and more special tasks that use computers and thus require print or screen display. Examples: -Data projectors: Projects the image onto a wall screen -Microfilm (COM): Computer Output Microfilm The computer directly generates the microfilm images. TOPIC QUESTIONS AND ANSWERS 1. When a computer prints a report, this is called Ans : Output 2. Output which is made up of pictures, sounds, and video is called Ans: Multimedia 3. An individual dot on a computer screen is called a Ans: Pixel 4. A screen which can only display white letters on a blue background is called Ans: Monochrome 5. Lists 4 output Devices you know Ans: Monitors, Projectors, Printers and Microfilm 6. Differentiate between a Parallel and Serial data Cable Ans: Serial is 1 bit and parallel is 8 bits 7. Give 3 types of Monitors you know? - Monocrome,CRT,plama screens,LCD

5- Storage What is Storage? Storage refers to the media and methods used to keep information available for later use. Some things will be needed right away while other won't be needed for extended periods of time. So different methods are appropriate for different uses. Earlier when learning about processing, we saw all the kinds of things that are stored in Main Memory.

Main Memory = Primary Storage Main memory keeps track of what is currently being processed. It's volatile, meaning that turning the power off erases all of the data. For Main Memory, computers use RAM, or Random Access Memory. These memory chips are the fastest, but most expensive, type of storage. Auxiliary Storage = Secondary Storage Auxiliary storage holds what is not currently being processed. This is the stuff that is "filed away", but is ready to be pulled out when needed. It is nonvolatile, meaning that turning the power off does not erase it. Auxiliary Storage is used for: ď&#x192;&#x2DC; Input - data and programs ď&#x192;&#x2DC; Output - saving the results of processing 30


So, Auxiliary Storage is where you put last year's tax info, addresses for old customers, programs you may or may not ever use, data you entered yesterday - everything that is not being used right now. Of the various types of Auxiliary Storage, the types used most often involve some type of magnetic disk. These come in various sizes and materials, as we shall see. This method uses magnetism to store the data on a magnetic surface. Advantages: high storage capacity, reliable and gives direct access to data A drive spins the disk very quickly underneath a read/write head, which does what its name says. It reads data from a disk and writes data to a disk. (A name that actually makes sense!) Types of Magnetic Disks 1. Hard Disks : These consist of 1 or more metal platters which are sealed inside a case. The metal is one which is magnetic. The hard disk is usually installed inside the computer's case, though there are removable and cartridge types, also. Technically the hard drive is what controls the motion of the hard disks which contain the data. But most people use "hard disk" and "hard drive" interchangeably. They don't make that mistake for floppy disks and floppy drives, described below. It is clearer with floppies that the drive and the disk are separate things.

2. Diskette / Floppy Disk (nearly extinct!) Sizes: 5Âź" (really old stuff)

3½" (pretty much gone now)

Both sizes are made of mylar with an oxide coating. The oxide provides the magnetic quality for the disk. The "floppy" part is what is inside the diskette covers - a very floppy piece of plastic (i.e. the mylar). These disks are rapidly vanished. New computers often come without a floppy disk drive at all unless you ask for one. Other Removable Magnetic Media Several other kinds of removable magnetic media are in use, such as the Zip disk. All of these have a much higher capacity than floppy disks. Each type of media requires its own drive. The drives and disks are much more expensive than floppy drives and disks, but then, you are getting much larger capacities. There are other kinds of storage devices that are not magnetic, such as flash drives, or are not disks, such as magnetic tape. Storage: Disk Format All magnetic disks are similarly formatted, or divided into areas, called -tracks -sectors -cylinders The formatting process sets up a method of assigning addresses to the different areas. It also sets up an area for keeping the list of addresses. Without formatting there would be no way to know what data went with what. It would be like a library where the pages were not in books, but were scattered around on the shelves and tables and floors. You'd have a hard time getting a book together. A formatting method allows you to efficiently use the space while still being able to find things. A. Tracks: A track is a circular ring on one side of the disk. Each track has a number. The diagram shows 3 tracks. 31


B. Sectors :A disk sector is a wedge-shape piece of the disk, shown in yellow. Each sector is numbered. On a 5¼" disk there are 40 tracks with 9 sectors each. On a 3½" disk there are 80 tracks with 9 sectors each. So a 3½" disk has twice as many named places on it as a 5¼" disk.

A track sector is the area of intersection of a track and a sector, shown in yellow

Clusters A cluster is a set of track sectors, ranging from 2 to 32 or more, depending on the formatting scheme in use. The most common formatting scheme for PCs sets the number of track sectors in a cluster based on the capacity of the disk. A 1.2 gig hard drive will have clusters twice as large as a 500 MB hard drive. 1 cluster is the minimum space used by any read or write. So there is often a lot of slack space, unused space, in the cluster beyond the data stored there. There are some new schemes out that reduce this problem, but it will never go away entirely. The only way to reduce the amount of slack space is to reduce the size of a cluster by changing the method of formatting. You could have more tracks on the disk, or else more sectors on a track, or you could reduce the number of track sectors in a cluster.

Cylinders A cylinder is a set of matched tracks. On a double-sided floppy, a track from the top surface and the same # track from the bottom surface of the disk make up a cylinder. The concept is not particularly useful for floppies. On a hard disk, a cylinder is made of all the tracks of the same # from all the metal disks that make up the "hard disk". If you put these all together on top of each other, you'd have something that looks like a tin can with no top or bottom - a cylinder.

The computer keeps track of what it has put where on a disk by remembering the addresses of all the sectors used, which would mean remembering some combination of the cylinder, track, and sector. Thank goodness we don't have to remember all these numbers! Where the difference between addressing methods shows up is in the time it takes for the read/write head to get into the right position. The cylinder method writes data down the disks on the same cylinder. This works faster because each metal platter has a read/write head for each side and they all move together. So for one position of the read/write heads, the computer can put some data on all the platters before having to move the heads to a new position. What happens when a disk is formatted? 1. All data is erased. Don't forget this!! 2. Surfaces are checked for physical and magnetic defects. 3. A root directory is created to list where things are on the disk. Disk Capacity The capacity of a magnetic disk depends on several factors. We always want the highest amount of data stored in the least possible space. (People are so greedy this way!) So the capacities of storage media keep increasing while cost keeps decreasing. It's a lovely situation for the user! 32


Capacity of a Disk depends on: 1. # of sides used: single-sided

double-sided

2. Recording density - how close together the bits can be on a track sector of the innermost track

3.Number of tracks on the disk

Capacity of Disks - 5Ÿ" floppy - 360 KB or 1.2 MB - 3½" floppy - 720 KB or 1.44 MB Hard disk -early ones = 20 MB -currently (July 2010) up to 3 TB Internal hard drive , where 1 TB = 1 terabyte = 1000 GB Caring for Disks There are fewer precautions for hard disks since they are more protected by being sealed in air-tight cases. But when damage does occur, it is a more serious matter. Larger amounts of data can be lost and hard disks are much, much more expensive that floppy disks. Hard disks can have problems from magnetic fields and heat like floppies do, but these are very rare Most problems occur when the read/write head (looks like a pointer in the photo) damages the metal disk by hitting or even just touching it. This is called a head crash. When the computer is on, the hard disk is spinning extremely fast. Any contact at all can cause pits or scratches. Every scratch or pit is lost data. Damage in the root directory turns the whole hard disk into a lovely doorstop! It's completely dead. So the goal here is to keep that read/write head where it belongs, just barely above the hard disk, but never, ever touching it. Don't -Jar the computer while the disk is spinning. -Turn the computer off and quickly back on before spinning has stopped. -Drop it - ever Caring for Data Besides protecting the physical medium you are using to store data, you must also consider what you can do to safeguard the data itself. If the disk is kept from physical harm, but the data gets erased, you still have a major problem. So what can you do to safeguard the data on which you rely?? Write protect This keeps your files from being overwritten with new ones. -Removable media including USB drives: 33


-Look for a tiny write-protect switch on the device. -Hard disks and devices without a switch: Make files Read-Only and/or Hidden to keep them from being overwritten. This is done by changing the file attributes using whatever system you have for managing files. -Assign a password to each file, which can be done with some programs and some USB drives. -Encrypt the files. This will require special software and remembering the decryption key. Backup Make multiple copies of important data often. The more important the files are, the more copies in more places you need. Anti-malware Use a set of programs that continuously look for an attack by a virus, Trojan, or worm . Computer viruses/Trojans/worms are sneaky computer programs that can erase your data and even your whole system. Many are merely annoying and are created as practical jokes. But there are a number of very damaging malware programs out there, plus others that are out to steal your passwords or use your computer to damage or annoy others. Your computer gets one of these nasties by downloading an infected file from the internet (sometimes without your knowledge!) or your office network, or by first using a removable disk in an infected computer and then accessing a file on that removable disk with your own computer. This makes it difficult to keep them from spreading. Once you have disinfected your computer, it can get re-infected from a removable disk that was used between the time you were infected with the malware and when you disinfected it. A number of nasty viruses hide for quite a while before doing their nasty things. So you can infect a lot of your own backups and other disks and spread the infection, all unknowingly, to others. So run an antimalware program that actively looks for infections all the time. Don't wait until you have symptoms. A lot of damage can be done before you figure out that you have a problem. Other Storage mediums include Magnetic Tape similar to the VCR tapes. It is a slow method of backup and is mostly used for very large amount of backup in multinational companies and institutions. Optical Disks An entirely different method of recording data is used for optical disks. These include the various kinds of CD and DVD discs. You may guess from the word "optical" that it has to do with light. You'd be exactly right! Laser light, in fact. Optical disks come in several varieties which are made in somewhat different ways for different purposes. How optical disks are similar - Formed of layers -Data in a spiral groove on starting from the center of the disk -Digital data (1's and 0's) 1's and 0's are formed by how the disk absorbs or reflects light from a tiny laser. The different types of optical disks use different materials and methods to absorb and reflect the light. How It Works (a simple version) An optical disc is made mainly of polycarbonate (a plastic). The data is stored on a layer inside the polycarbonate. A metal layer reflects the laser light back to a sensor. To read the data on a disk, laser light shines through the polycarbonate and hits the data layer. How the laser light is reflected or absorbed is read as a 1 or a 0 by the computer. In a CD the data layer is near the top of the disc, the label side. In a DVD the data layer is in the middle of the disc. A DVD can actually have data in two layers. It can access the data from one side or from both sides. This is how a double-sided, double-layered DVD can hold 4 times the data that a single-sided, single-layered DVD can.

Materials The materials used for the data (recording) and metal (reflecting) layers are different for different kinds of optical disks. 34


Read Only: The most common type of optical disk is the CD-ROM, which stands for Compact Disc - Read Only Memory. It looks just like an audio CD but the recording format is quite different. CD-ROM discs are used for computer software. DVD used to stand for Digital Video Device or Digital Versatile Device, but now it doesn't really stand for anything at all! DVDs are used for recording movies and large amounts of data. The CDs and DVDs that are commercially produced are of the Write Once Read Many (WORM) variety. They can't be changed once they are created. The data layer is physically molded into the polycarbonate. Pits (depressions) and lands (surfaces) form the digital data. A metal coating (usually aluminum) reflects the laser light back to the sensor. Oxygen can seep into the disk, especially in high temperatures and high humidity. This corrodes the aluminum, making it too dull to reflect the laser correctly. CD-ROM and DVD-ROM disks should be readable for many, many years (100? 200?), but only if you treat them with respect. Write Once: The optical disks that you can record on your own computer are CD-R, DVD-R, and DVD+R discs, called writable or recordable disks. The metal and data layers are separate. The metal layer can be gold, silver, or a silver alloy. Go for the Gold: Gold layers are best because gold does not corrode. Naturally, the best is more expensive. Sulfur dioxide from the air can seep in and corrode silver over time. Rewrite: An option for backup storage of changing data is rewritable disks, CD-RW, DVD-RW, DVD+RW, DVD+RAM. The data layer for these disks uses a phase-changing metal alloy film. This film can be melted by the laser's heat to level out the marks made by the laser and then lasered again to record new data. In theory you can erase and write on these disks as many as 1000 times, for CD-RW, and even 100,000 times for the DVDRW types. Advantages of Optical Disks 1. Physical: An optical disk is much sturdier than tape or a floppy disk. It is physically harder to break or melt or warp. It's somewhat harder to lose than a USB flash drive. 2. Delicacy: It is not sensitive to being touched, though it can get too dirty or scratched to be read. It can be cleaned! 3. Magnetic: It is entirely unaffected by magnetic fields. 4. Capacity: Optical disks hold a lot of data, especial the double-sided DVDs. Plus, the non-data side of the disk can have a pretty label! Disadvantages of Optical Disks 1. Cost: The main disadvantage has been cost. The cost of a CD-RW drive has dropped drastically and quickly You have to be careful about the capacity and maximum recording speed. The boxes all look a lot alike! So for commercial use, the read/write drives are quite cost effective. For personal use, they are available and are cheap enough to use for data storage for everyone. 2. Duplication: It is not quite as easy or as fast to copy an optical disk as it isto copy files to a USB flash drive. You need the software and hardware for writing disks! (This is an advantage as far as commercial software providers are concerned!) But discs are easy to label and to store. Care of Optical Disks (CDs, DVDs) Your CDs and DVDs are not going to last forever. They certainly store data longer than other storage media! Mis-handling your optical disk can quickly make your data unreadable. Even fingerprints can do damage over time. Data loss comes from: 35


-Physical damage - breaking, melting, scratching... - Blocking of laser light by dirt, paint, ink, glue... - Corrosion of the reflecting layer Here are some do's and don'ts for keeping your CDs and DVDs healthy. Cleaning: o Keep it clean! o Handle by the edges or center hole. o Put it back in its case as soon as you are finished with it. No laying around on the desktop!! o Remove dirt and smudges with a clean cotton cloth by wiping from the center to the outer edge, NOT by wiping around the disk. Wiping in a circle can create a curved scratch, which can confuse the laser. o For stubborn dirt, use isopropyl alcohol or methanol or CD/DVD cleaning detergent. Labeling: o Don't use an adhesive label. The adhesive can corrupt your data in just a few months! o Don't write on or scratch the data side of the disk - ever! o Don't scratch the label side. o Don't write on the label side with a pencil or pen (scratches!) o Don't write on the label side with a fine-point marker or with any solvent-based marker. Use markers for CDs. (Solvent may dissolve the protective layer.) Storage: o Store optical disks upright on edge, like a book, in a plastic case designed specifically for them. Not flat for long periods! o Store in a cool, dark environment where the air is clean and dry. NO SMOKE! Low humidity. How you treat it: o Keep away from high heat and high humidity which accelerate corrosion. o Keep out of sunlight or other sources of ultraviolet light. o Keep away from smoke or other air pollution. o Don't bend it! o Don't use a disk as a coaster or a frisbee or a bookmarker! Recording - Check disk for flaws and dirt BEFORE recording on it. - Only open a recordable disk just before you plan to record on it. - After recording, make sure the disk works as you expect: Read data; run programs. Flash Memory Several different brands of removable storage cards, also called memory cards, are now available. These are solid-state devices (no moving parts) that read and write data electrically, instead of magnetically. Devices like digital cameras, digital camcorders, and cell phones may use CompactFlash, SmartMedia, Memory Stick, or another flash memory card. Laptop computers use PCMCIA cards, another type of flash memory, as solid-state hard disks. USB drive This new type of flash memory storage device does not yet have a generally accepted name. Each company calls it something different, including flash drive, jump drive, flash pen, thumb drive, key drive, and mini-USB drive. All are small, about the size of your thumb or a large car key, and plug into a USB port on the computer. No drivers are needed for recent versions of Windows. Plug it in and the computer reports a new drive! Such small flash drives can have storage capacities from 8 MB to 128 GB or more! Some flash drives include password protection and the ability to run software right off the USB drive. So cool! Removable hard drives Several types of special drives that compress data are available. An external hard drive can be used for backup, too. The image at the right is of an external Zip drive with a disk sticking out.

36


Mass storage: Businesses with very large sets of data that need easy access use sets of cartridges with robot arms to pull out the right one on command. Smart cards: A chip on the card itself tracks changes, like deducting purchases from the amount entered originally on the card. Smart cards are already used in Europe and at colleges instead of using a handful of coins at vending machines and at laundromats. Another use involves a new sensor technology which lets a smart card read your fingerprint right on the card. The digital image of the fingerprint is then transmitted to a database to compare it with the one on file for that card. You can prove you are really you!! Optical cards: A chip on the card holds information like health records and auto repair records. They can hold more data than the smart cards since they don't need to do any processing. Topic Questions and Answers 1. Define a Storage device and give 3 examples of a storage device ANS: Examples include USB flash Disk, DVD-ROM, Hard Drive, RAM, Smart Cards etc. 2. Differentiate between Primary Storage and Secondary storage devices. ANS: Primary we have RAM, secondary we have hard drives 3. The most commonly used auxiliary storage device(s) is/ are ANS: USB drives and tapes 4. What is the effect of formatting a hard drive of a computer? ANS: All data is erased 5. A gigabyte is equal to ANS: 1000000000 bytes 6. Tape storage is primarily used for ANS: BACKUP 7. The type of auxiliary storage which uses a laser is call ANS: OPTICAL DISK 8. What is the full meaning of DVD? ANS: Digital Versatile Disk (Digital Video Disk)

37


CHAPTER 4 COMMUNICATION Computer communication is the transmission of data and information over a communications channel between two computers, which can be several different things.

Communications between computers can be as simple as cabling two computers to the same printer. It can be as complex as a computer at NASA sending messages through an elaborate system of relays and satellites to tell a computer on Mars how to drive around without hitting the rocks. Depending on the context, for computer communications you might use the terms:   

Data Communications for transmission of data and information over a communications channel Telecommunications for any long-distance communications, especially television Teleprocessing for accessing computer files located elsewhere

Communications Channel A communications channel, also called a communications line or link, is the path that the data follows as it is transmitted from one computer to another. Below is an animation of a communications channel at work. A PC is sending a message to a host computer clear across the country. Notice the variety of transmission methods used: telephone lines, satellite links, microwave relay. This is a simplified version of what really goes on! (The animation runs 10 times and stops. To restart it, use your browser's Refresh command.)

Transmission Media :With such complex communications channels, we need to be aware of the capabilities and limitations of the various media in use. Transmission media just means the physical materials that are used to transmit data between computers. Cable For communications between computers that are linked by cable, there are three choices. 

Twisted wire (phone line) 38


Advantage: Easy to string ,Cheap Disadvantage: Subject to interference = static and garble  Coaxial cable (round insulated wire) Advantage: Not susceptible to interference and Transmits faster Disadvantage: Heavy & bulky Needs booster over distance  Fiber optic line (glass fibers) Advantage: Smaller Lighter and Faster No interference Disadvantage: Expensive and Harder to install and modify  Broadcast For longer distances or when cables are not practical, other transmission media come into play. We're getting really high tech here! It may seem odd to call microwaves, radio waves, or light a "physical" medium. All are electromagnetic in nature. Sometimes they are treated by scientists like streams of teeny, tiny particles and other times like waves on the beach. In their "particle" life, they do behave like a bunch of physical particles. So it's not quite as odd as it first appears. (But all those electromagnetic things are plenty odd!)  Wireless (infrared, light, radio) Advantage: Flexible and Portable Disadvantage: Slower data transfer than hard-wired methods and Subject to interference  Microwave Advantage: Speed of light and Uses a few sites Disadvantage: Line-of-sight only  Satellite Advantage: Always in sight Disadvantage: Expensive uplink and downlink facilities Signals Two types of signals are used for data transmission: Digital and Analog. A digital signal is a stream of 0's and 1's. So this type is particularly appropriate for computers to use. An analog signal uses variations (modulations) in a signal to convey information. It is particularly useful for wave data like sound waves. Analog signals are what your normal phone line and sound speakers use. Modems Often communications between computers use the telephone system for at least part of the channel. A device is needed to translate between the analog phone line and the digital computer. Such a device is the modem, which comes from Modulate/Demodulate, which is what a modem does. It modulates a digital signal from the computer into an analog one to send data out over the phone line. Then for an incoming signal it demodulates the analog signal into a digital one. Transmission Rate Confusion abounds when it comes to measuring the transmission rate of a modem. Throughput is the term for the entire process - how much data is moved during a certain amount of time. Since the modem is only part of the process of moving data, getting a faster modem may not speed up your data transfers. There are two different parts of the data transfer to measure: the digital process and the analog process. Digital The rate of digital transmission is measured in bits per second (bps). Common rates for regular modems are 28.8 Kbps, 33.6 Kbps, and 56 Kbps where the K stands for thousand. Completely digital devices (discussed below) are much faster. Faster is better, of course. 2400 bps would send a 20-page single-spaced report in 5 min. (This is SLOW!!) Analog 39


The analog side is measured in baud where 1 baud is one change in the signal per second. Most people use bps and baud as though they were the same. For speeds of 2400 bps and under, this is true, but is it not so for the higher speeds where more than one bit is transmitted per signal change. Physical types There are three physical types of modems:  External which plugs into a serial port on the back of the computer Advantages: Can be moved to a different computer easily. Does not take up a slot inside the computer. Lights on front are visible to show what the modem is doing. Disadvantages: Takes up deskspace. Adds more cables to the tangle.  Internal where the phone line plugs directly into card through the back of the computer Advantages: Saves deskspace. Saves a cable. Disadvantages: Requires an internal peripheral slot. (They get filled up.) Must use software display to see the lights that show what the modem is doing.  Acoustical where the telephone handset is placed into the device, which is connected to the computer (Old technology! Not many of these around any more.) Advantages: Can use a phone without having to move the phone wire. Disadvantages: Bulky. Connection much more prone to static and interference. Only a standard handset will fit. Digital Modems A digital modem does not have to convert between analog and digital signals. Technically it's not a "modem" at all since it is not modulating and demodulating. A digital modem is faster than an analog modem. To get the increase in speed you will have to pay extra (of course!). Digital modems are more expensive and so are digital data lines from the phone company. The phone company has to install additional equipment for some kinds of digital modems. Normally a digital modem can receive data at a much higher rate than it can send it out. That works out fine for most people because they are only sending out a few responses instead of whole web pages or data files. Types of Digital Modems ISDN modem (Integrated Services Digital Network) - a digital device using a digital phone line. It actually should be called a terminal adapter, but the name modem has stuck. An ISDN device is capable of higher rates than a normal modem, 64 Kbps for a single line and 128 Kbps for a bonded dual line. ISDN adapters cost more than normal modems and also require special arrangements with the phone company (and more $$ for them, of course!). Fiber optic line is best for the highest ISDN transmission rate, but the copper wires used in most homes and offices will work also. Note: To get the highest speeds out of your ISDN modem, you'll need a high speed I/O (input/output) card in the computer to which to connect the modem.  

DSL (commonly used for ASDL) (Asymmetric Digital Subscriber Line) - a new technology that allows a single regular telephone line to serve for normal phone calls and digital data at the same time. An ADSL modem receives data (downloading) at rates ranging from 384 Kbps to 8Mbps, depending on the particular kind of service. Even the slowest type is 4 times faster than the best ISDN! The sending (uploading) rate is much slower, thus the "asymmetric" part of the full name for this kind of service. That is not a problem for most people since they do not need to upload much data at a time. Besides great speed, ADSL does not require a separate phone line and you are connected all of the time. No more dialing up! You can use a regular phone on the same line and at the same time that you are surfing the Internet. No more busy signals to your friends and relatives! Cable modem Hooks up to your cable TV line and can receive up to 1.5 Mbps or more. You must have cable TV service with a cable company that also provides data service. You may need a special cable box to which you connect your TV and your computer. You will be sharing the line with all of the cable customers hooked up to your particular cable line. The actual transfer rate you get will depend on how many people are using the cable at the same time. Once cable modems become popular in your neighborhood, your speed will slow down noticeably. Most companies 40


now restrict the top speed level and balance the load better than they used to do. A cable modem connection is certainly faster than ISDN. Most cable accounts are faster than most DSL accounts. How Device Speeds Compare The table below will help you see just how much faster the different transfer rates are. To read the table, look at the speed in the top row, which is in kilobytes per second. Below it you will see how long it takes to transfer 1 MB, 10 MB, and 1000 MB at that speed. Check out the last row. This one really shows the difference between analog modems and the digital kind. The times go down from days to hours or even minutes! Remember that just because your device is able to send and receive at a certain rate does not mean that it will ever actually work that fast. There are many other factors in the communications channel that can reduce the transmission speed from the maximum.

Protocols To talk to each other, modems have to exchange a good bit of information, since there are so many different types and speeds of modems around. That's what the high pitched squeals and squawks are that you can hear when an analog modem is trying to connect. It's modem talk for "So, who are you? Do you speak my language? Well, maybe we can find a common language so these guys can get connected." A digital modem does not make noises (an advantage!) but it must do the same kind of negotiation with the device at the other end to come up with a common language, called a protocol. A protocol defines what information is exchanged and in what order. The names of the protocols are of the form v.##. So you'll see things like v.25bis, v.34, and v.120. Some protocols are more stable or faster than others at certain tasks. You can't just hook up your computer to a network or a modem and start sending and receiving data. The computer needs instructions on how to do this. You need some kind of communications software. Since there are a number of different communications tasks, there are different kinds of programs that manage those tasks. Dialing Dialing software tells the computer how to place a call on the phone line connected to it. It also displays messages about the progress of the call or lack thereof. A list of phone numbers for frequently called, or frequently forgotten, numbers is an important feature. File Transfer One of the most common uses of computer to computer communications is to transfer files from one to the other. Downloading means to transfer a file to your computer from elsewhere. Uploading means to transfer a file from your computer to another. Programs that manage this process include many file management features. You need to be able to see what files are available, their sizes, and the folders you can put the transferred file in. You may want to rename the file or create a new folder for your new file. Such a program will also handle the process of connecting to the other computer. Many of the names of these programs include the letters FTP, which stands for File Transfer Protocol. (Yes, another kind of protocol. And there are more!!) Data Encryption When sending data over a communications channel, there is always the possibility that someone will see your data that you didn't mean to. If your data is of a sensitive nature, like your credit card number, or if it is secret, like the formula for CocaCola, you'd probably like to keep strangers from reading it. 41


A data encryption program encodes your data, just like spies do. So to read it, a person would need the right decoding program and the right password or file to give that program so it would know what to do exactly. Networks A network is a set of computers which are linked together on a permanent basis. This can mean two computers cabled together on the same desk or thousands of computers across the world. Advantages: Enables users to share hardware like scanners and printers. This reduces costs by reducing the number of hardware items bought. Allows users access to data stored on others' computers. This keeps everyone up-to-date on the latest data, since it's all in the same file, rather than having to make copies of the files, which are immediately out-of-date. Can even let users run programs that are not installed on their own computers but are installed elsewhere in the network. This reduces the effort for networks administrators to keep programs configured correctly and saves a lot of storage space. Disadvantages: Accessing anything across a network is slower than accessing your own computer. More complexity adds new problems to handle. Less customization is possible for shared programs and folders. Everyone will have to follow the same conventions for storing and naming files so others can find the right files. LAN A LAN is a Local Area Network. This would include networks where the computers are relatively close together. So LANs would be within the same office, a single building, or several buildings close together. The graphic at the right shows two buildings with 4 departments connected as a LAN.

WAN A WAN is a Wide Area Network, which would be all networks too large to be LANs. There doesn't seem to be a clear line between the two designations. A WAN would be most useful for large companies with offices or factories in widely separated areas, like Microsoft, IBM, Ford, AT&T, etc. MAN A man stands for Metropolitan Area Network , and it is just like WAN and it is capable of linking different offices in different towns together Network Configurations (Topology) There are a number of ways that computers can be connected together to form networks. The pattern of connections depends in part on the distances involved since that determines what hardware must be used. It also depends on the degree of stability needed for the network. That is, how important is it that the whole system can't crash at the same time. These choices carry dollar costs, too. Better costs more, sometimes a LOT more. Each device in the network, whether it's a computer, printer, scanner, or whatever, is called a node. Star Topology

The star pattern connects everything to a host computer or a network hub, which handles the network tasks. All communications between computers go through the host/hub. This configuration is good for home networks, often using a 42


wireless hub. Using a very large host computer, it is good for businesses that have large amounts of rapidly changing data, like banks and airline reservation offices. Advantages: Gives close control of data. Each PC sees all the data. User sees up-to-date data always. If a computer other than the host fails, no other computer is affected. Disadvantages: If host computer or its software goes down, the whole network is down. (A backup computer system would be necessary to keep going while repairs are made.) Bus Topology The bus pattern connects the computer to the same communications line. Communications goes both directions along the line. All the computers can communicate with each other without having to go through the server. Advantages: Any one computer or device being down does not affect the others. Disadvantages: Can't connect a large number of computers this way. It's physically difficult to run the one communications line over a whole building, for example.

Ring Topology The ring pattern connects the computers and other devices one to the other in a circle. There is no central host computer that holds all the data. Communication flows in one direction around the ring. This configuration is good when the processing of data can be done on the local PC. Advantages: Requires less cabling and so is less expensive. Disadvantages: If one node goes down, it takes down the whole network. In the token ring form of a ring network, a token is constantly passed along the network. A device must wait until the token is at that device. Then it can attach the message it wants to send to the token. When the token reaches the intended recipient device on the network, it will release the message. The token circulates very fast, but this obviously means that most of the time a device will have to do some waiting before it can send out a message. Others include Wireless Topology, Hybrid Topologies such as the Star-ring, Mesh, etc. Connecting Networks Networks can be connected to each other, too. There are difficulties in doing so, however. A combination of software and hardware must be used to do the job. ď&#x201A;ˇ A gateway connects networks of different kinds, like connecting a network of PCs to a main frame network. This can be complex! ď&#x201A;ˇ A bridge connects networks of the same type. This job is simple. ď&#x201A;ˇ A router connects several networks. A router is smart enough to pick the right path for communications traffic. If there is a partial failure of the network, a router looks for an alternate route. Suppose the accounting, advertising, and shipping departments of a company each have networks of PCs. These departments need to communicate with each other, but only sometimes. It would be easier and cheaper to connect them to each other than to put them all on the same larger network. The best arrangement would be for the departmental networks to be of the same kind so that a bridge could be used. Topic Questions and answers 1. Define a Communication channel? Ans: The path that data travels between two computers,or devices. 2. Name two types of Transmission Media Ans: Coaxial Cable, and Twisted Wire. 3. What is the main advantages of Optic fibres above all other transmission media Ans: Capable of having no interference. 4. The main function of a Modem is Ans: change incoming analog signals to digital signals and outgoing digital signals to analog signals

43


5. What is the meaning of File Transfer? Ans: To move a copy of a file from one computer to another over a communications channel 6. Define A LAN? ANS: Local Area Network 7. Sharing of hardware resources like a scanner could be done with what type of network architecture? Ans: Local Area Network 8. Give one disadvantage of a Star Topology? Ans: The breakdown host/hub breaks down the whole network. 10. Give three uses of a Computer network? Ans: Sharing of resources such as printers, Sharing of Files and Folders, Easy deployment of software applications.

CHAPTER 5 Programming Do you wish you could change some of your software to work just the way you want it to? Do you sometimes think "I could do better than THIS!" when your software crashes? Well, maybe you can!! It will take some work, of course. What you'd have to learn is how to program your computer. While I can't teach you how to do that in this series of lessons (Breathe a sigh of relief now!), you can learn a little about what programming is all about. What is a computer program? Simply put, a computer program is a set of detailed directions telling the computer exactly what to do, one step at a time. A program can be as short as one line of code, or as long as several millions lines of code. (We'll hope those long ones do a lot of different and complex things!) . Language Types Programming has changed a lot since the first computers were created. The original programs were very simple and straight forward compared to today's elaborate databases, word processors, schedulers, and action games. Different computer languages have been created with which to write these increasingly complex computer programs. They can be categorized based on how close to normal speech they are, and thus how far from the computer's internal language. Machine Languages The language of the CPU (The central processing unit of the computer, which is the part that does the "thinking"). The lowest level language. Composed of 0's and 1's Assembly Languages Abbreviations for machine language High-Level Languages Use program statements - words and algebra-type expressions. Developed in the 50's and 60's. After a program is written in one of the high-level languages, it must be either compiled or interpreted. A compiler program rewrites the program into machine language that the CPU can understand. This is done all at once and the program is saved in this new form. A compiled program is generally considerably larger than the original. An interpreter program translates the program statements into machine language one line at a time as the program is running. An interpreted program will be smaller than a compiled one but will take longer to execute. 4th Generation Languages = 4GL. Very high-level languages. These are results oriented and include database query languages. There are fewer options for programmers, but the programs are much easier to write than in lower level languages. These too must be compiled or interpreted. Natural Languages 5th Generation Languages. We don't really have any programming languages yet that use natural language. In such a language you would write statements that look like normal sentences. For example, instead of odd-looking code you would write "Who are the salesmen with sales over 20,000frs CFA last month?"

44


Many computer languages are available for writing computer programs. They each have advantages for certain kinds of tasks. Let's check out some examples of the various types of computer languages and see what they are used for. Machine Language = the native tongue of the CPU. Each design for a CPU has its own machine language. This is the set of instructions that the chip uses itself. So it is made up of sets of 0's and 1's, that is binary numbers. Very hard for people to work with.

Here's another example of machine language. The segment of Java code: int counter = 0; counter = counter + 1; might be translated into machine language as: 000101000100010001000100001000101010111110 000001110101000111110000100010000010101010 Assembly Language = Codes or abbreviations for the machine language instructions In an assembly language each machine language instruction is assigned a code. So instead of having to remember a string of 0's and 1's, the programmer would only need to remember short codes like ADD, MOV, or JLE. Certainly an improvement over 000101000100010001000100001000101010111110!! But not really "user friendly" either. The assembly language program below reads two characters and prints them on the screen. The text to the right of the semicolons ( ; ) is ignored by the computer. It's there to explain the program to anyone looking at the code. Notice that each little step must be coded. All this just to display 2 characters!

FORTRAN = Formula Translation FORTRAN was created around 1957 to help scientists, engineers, and mathematicians write programs that describe complex situations, like nuclear power plant monitoring, nuclear explosions, and space flight. This is still a widely used language. It was the first successful high-level program. Newer versions have been released. The most recent standard version is Fortran 2008 which was finalized Sept. 2010. (Originally FORTRAN in all caps was required but recent version names can use normal case.) The example Fortran program below accepts the bus number 99 and displays the command "TAKE BUS 99" PROGRAM IDEXMP INTEGER BUS_NUM BUS_NUM = 99 WRITE(*,*) ' TAKE BUS ', BUS_NUM 45


END COBOL = Common Business Oriented Language COBOL was written about 1960 with business applications in mind. It has a very English-like structure, using sentences and paragraphs, though they are certainly different from those in a novel. This helps business people who are not high-powered programmers to be able to write or edit a program. But it has the disadvantage of tending toward wordy, lengthy programs. It is a good language for direct, simple programs. COBOL was used to create many programs for the main frames of large companies. These programs were upgraded during the Y2K fixes for the year 2000. So it seems likely that COBOL programs will be around for a long time yet. The example below accepts two numbers, multiplies them, and displays the numbers and the result. Look at the PROCEDURE DIVISION to see where the calculation is done. $ SET SOURCEFORMAT"FREE" IDENTIFICATION DIVISION. PROGRAM-ID. FragmentA. AUTHOR. Michael Coughlan.

DATA DIVISION. WORKING-STORAGE SECTION. 01 Num1 PIC 9 VALUE ZEROS. 01 Num2 PIC 9 VALUE ZEROS. 01 Result PIC 99 VALUE ZEROS. PROCEDURE DIVISION. Calc-Result. ACCEPT Num1. MULTIPLY Num1 BY Num2 GIVING Result. ACCEPT Num2. DISPLAY "Result is = ", Result. STOP RUN. BASIC = Beginner's All Symbolic Instruction Code This language was written in 1964 (truly the age of dinosaurs for computers!) for college students to use to learn programming concepts. Originally BASIC was intended only for classroom use. But the language has proven to be highly useful in the real world. A wide variety of "dialects" of BASIC developed through the years. Visual Basic is now very popular for programming Windows applications. Microsoft Visual Basic for Applications is an example of a subset of BASIC that is modified to help users write small subprograms called scripts or macros for use with applications like MS Word. Some applications used to have their own variety of BASIC for writing their macros, like Word Basic and Excel Basic. The creators of BASIC wanted a language that felt more like regular English. So while it doesn't LOOK much like English, it uses enough of the syntax of English to give it a more natural feel than many other computer languages. The short program below is written in BASIC. It accepts a distance in miles, yards, feet, and inches and converts it to kilometers, meters, and centimeters. Notice how the programmer can write equations to do the calculations. ' English to Metric Conversion ' J. S. Quasney ' **************************** PRINT : PRINT "English to Metric Conversion" PRINT INPUT "Miles: ", Miles INPUT "Yards: ", Yards INPUT "Feet: ", Feet INPUT "Inches: ", Inches Inches = 63360 * Miles + 36 * Yards + 12 * Feet + Inches 46


Meters# = Inches / 39.37# Kilometers = INT(Meters# / 1000) Meters# = Meters# - 1000 * Kilometers Final.Meters = INT(Meters#) Centimeters = Meters# - Final.Meters Centimeters = 100 * Centimeters Centimeters = INT((Centimeters + .005) * 100) / 100 PRINT PRINT "Kilometers:"; Kilometers PRINT "Meters:"; Final.Meters PRINT "Centimeters:"; Centimeters END C - Originally created for writing system software, C has evolved into C++. Both are widely used by programming professionals for all sorts of programs. The program below is written in C++. It accepts 3 numbers and checks to see if the third is equal to the difference of the first two. #include <iostream.h> void main() { int a, b, c; cout << "Please enter three numbers\n"; cout << "a: "; cin >> a; cout << "\nb: "; cin >> b; cout "\nc: "; cin >> c; if (c=(a-b)) { cout << "a: "; cout << a; cout << " minus b: "; cout << b; cout << " equals c: "; cout << c << endl; } else cout << "a-b does not equal c:" << endl; Java- The language Java is used to write both full computer applications and small applets for web pages. Its goal is to create applications that will run on any computer unlike other languages which are not cross-platform. For example, MS Word for Windows will not run on a Macintosh or Unix computer. You must buy the version of MS Word that is written for your particular operating system. (By the way, don't confuse Java with JavaScript, a scripting language commonly used on web pages. The only thing they share is the letters in their names! JavaScript started life as LiveScript in about 1994. Netscape bought it and renamed it, apparently for marketing reasons.) The example below draws a box on an HTML page and counts the number of times you have clicked inside the box. import java.applet.*; import java.awt.*; public class exfour extends Applet { 47


int i; public void init() { resize(300,300); } public void paint(Graphics g) { g.drawString("You clicked the mouse "+i+" Times",50,50); } public boolean mouseUp(Event e, int x, int y) { i++; repaint(); return true; } }

Creating What is involved in writing a computer program? What kinds of decisions must be made? Who is involved? Is it hard? (I'll bet you can guess the answer to that last one!) The process of creating a computer program is not as straight-forward as you might think. It involves a lot of thinking, experimenting, testing, and rewriting to achieve a high-quality product. Let's break down the process to give you an idea of what goes on. What Task? The first decision to make when creating a computer program is: What is this program supposed to do? The more detailed this description is, the easier it will be to get good results. What Language? The choice of what computer language to use has important consequences for how easy the program will be to write and maintain. The graphic shows some of the most commonly used languages and what tasks they are usually used for.

The languages are grouped by how complex they are for the writer. The simplest with the least power are at the bottom. Simple languages for simple tasks. (But how simple is any of this, really??) Things to consider in choosing a language Works with what you've got  Existing standards in your company  Existing hardware  Existing software with which to interact  Programmers' current knowledge Will work in the future  With variety of hardware  Changes easy to make in programs  Errors easy to find in programs 48


Who's Involved? What people are involved in the creation of a new computer program? ď&#x201A;ˇ The End User sets the tasks to be done. What does the customer want to do?? ď&#x201A;ˇ A Systems Analyst designs the overall requirements and sets the strategy for the program. ď&#x201A;ˇ A Programmer writes the actual code to perform the tasks. There may be a huge team of dozens of people involved. Or perhaps one programmer decides that he can write a program that is the answer to what users complain about. It may be done in a highly structured series of conferences and consumer surveys. Or perhaps someone is listening to what people say as they go about trying to work. Somehow the needs of the end users must be understood as well as the limitations of the code and the hardware. Costs come into play, too. (Sad but true.) All of these people must communicate back and forth throughout the process. No program of any size will be without unexpected problems. So it's test and fix and test again until the program actually does what it was intended to do. Program Development A program goes through the following steps over and over during its development, never just once.

1. 2. 3. 4. 5.

Set & Review goals: What is it supposed to do? Design: Create the strategy to achieve goal. Coding: Write the program. Testing: Try it out with real people. Documentation: What you did and why. How to use it.

One of the techniques used during the design phase is to flowchart the program, as on the right. Different shapes represent different kinds of steps, like input and output, decisions, calculations. Such charts help keep the logic clear, especially in complex programs. Each time through the development loop, the program must be debugged. This means testing the program under all conditions in order to find the problems so they can be handled. There will always be problems. Sometimes it's just a typo, and sometimes it's a flaw in the logic, and sometimes it's an incompatibility with the hardware or other software. Handling such situations can be the most time-consuming part of the whole process! Proper documentation can make or break a program. This includes explanations to the end user of how to use the program and also internal notes to programmers about what the code is doing and why. It is amazing how quickly the original coder can forget why he wrote the code that way! Programs often need to be maintained, that is, changes must be made. For example, the sales tax rate might change or zip codes may get more digits. With proper internal documentation, a different programmer can make these adjustments without damaging the program. Topic Questions and answers 1. Who designs the structure of a computer program? Ans: System Analyst 2. Checking a computer program for errors is called? Ans: Debugging 3. The computer itself uses what type of computer program? Ans: Machine Language 4. The term BASIC is an acronym for? Ans: Beginner's All-purpose Symbolic Instruction Code 5. A programming language which looks like normal English is called? Ans: A natural Language 6. The process of writing the computer instructions is called? Ans: Coding

49


7. The most widely used language for business programs is called ? Ans: FORTRAN 8. Why is Documentation of computer programs so important ? Ans: So that the user can easily learn how to use the program, other programmers could easily understand correct errors if need be and lastly so that other programmers can also understand why the program is built that way.

CHAPTER 6 APPLICATIONS An application is another word for a program running on the computer. Whether or not it is a good application depends on how well it performs the tasks it is designed to do and how easy it is for the user to use. That involves the user interface - the way the user tells the software what to do and how the computer displays information and options to the user. Text Interface A text interface was all that was available in the beginning. The example below is of PKZIP, which squashes files into smaller size to save space. Notice in the center the command you would have to type to use this program. An actual command line would look something like: c:\>pkzip c:\myfiles\newfile.zip c:\docs\report14.doc A text-based interface means typing in all the commands. If you mis-type, you have to backspace to your error, which erases what you already typed. It's hard to have fun this way! Add-on programs were written, of course, so you could edit what was typed - to the joy of all who had to work with long command lines. Modern text interfaces have lots of cool shortcuts and features. But you still have to spell and type well. Text Interface with Menus Improvements arrived with the addition of menus aaround the screen. The example to the right is of an old bulletin board companywould post messages and reply to other people's messages. Notice the list of commands in the popup menu in the center. You would use the arrow keys to move up the Enter key to execute the command. Various menus were usually available by using the ALT key in centre key. Graphical Interface A graphical user interface (GUI - sometimes pronounced GOO-ee) uses pictures to make it easier and It is more user friendly. The example below is from an old versions of Windows. The use of drop-down menus, windows, button and icon marketed by Apple on the Macintosh computer. These ideas are now as standard for graphical interface Common features of a graphical interface: The image below is an animation. It may take a moment to complete loading, then the image will change (Yes, the style in the animation is old, but the parts are the same for the newer, smoother versions):

There are many different kinds of applications, all with lots of spiffy features. Word processing is the application that is used most often and most widely. We will start with i to learn about the terms and features that are common to most applications, as well as some that are specific to word processing. Then we will look at other major applications and what they do. Examples of word processing programs: Microsoft Word, WordPerfect, Lotus WordPro, and Open Office Writer. Word Processing 50


Word processing is the most used computer application! It has replaced the typewriter as the main way words are put on paper. Documents can be revised and corrected before they are ever printed. An existing document can be used as a template, or pattern, for a new one. So the user doesn't have to recreate standard documents from scratch each time. This is a major time-saver and helps keep things consistent. Purpose: To produce documents Main advantage: Can easily change what has been done Can reuse existing documents as a template Steps to produce a document Create Edit Format Print Save (often!!) Let's look at the terms involved in these steps more closely. Most of these terms also apply to the other standard applications, so we will not redefine them for all. 1. Create You create a document when you open a blank document and enter text. Features/Terms: Word wrap - automatically wrapping the text to the next line so it all fits within the screen's width. Change the size of the screen and the text moves to fit in the space. Cursor - Symbol for where text will appear like: Enter textType new text Scrolling - moving document around within window Select - Highlight text, usually by dragging. Commands and keystroke combinations will apply to the selected material. Edit - make changes Cut - remove selection from document and store temporarily on the Clipboard, which is a section of computer memory. The Windows Clipboard can hold only one thing at a time. The Office Clipboard from Office XP and later versions can hold many items. Copy - duplicate selection onto Clipboard Paste - place contents of the Clipboard at cursor location Undo - reverses whatever change you just made Some programs will only "undo" the last change. Others keep a list and can undo more, depending on how many changes the program tracks. Insert - add text at location without overwriting existing text Overwrite - typing overwrites existing text, replacing whatever characters were there already Delete - remove text (not saved anywhere) Search - look for specific word(s) or character(s) Replace - can replace specific word(s) or character(s) with stated text Template - a document that serves as a pattern for a new document Thesaurus - looks for synonyms for selected word Spelling check - looks for spelling errors Grammar check - looks for grammar/style errors (of limited help) Do it! Would you like to play around with the basic word processing skills? Try the Do It! practice page. Both versions will open in a new window. Do It! - framed Do It! - no frames For a full set of lessons on word processing, go to the section: Working with Words

2. Format Once a document has been created, or during the process, you arrange how it will look by selecting the kind of letters and their sizes and colors, how much space is left and where, how things line up. This is formatting the document. Features/Terms: 51


Typeface - set of characters of similar design like: Point size - one point = 1/72 of an inch like: 12 pt. 18 pt. 24 pt. 36 pt. Font - combo of typeface & point size, includes styles such as BOLD, italics, underline Margins - space at the page borders Justification - left center right justify Spacing - space between letters and lines Borders/shading - lines around table or page; background color Headers/footers - info to repeat on each page Style sheets - saved sets of formats to reuse Columns - columns of text side by side as in a newspaper Tables - items listed in rows and columns Graphics - pictures and charts Print - When a document is finished, it may be printed onto paper. Features/Terms: Choose number of copies/pages to print Choose Orientation: Portrait / Landscape Print Preview - shows you how it will look in print Desktop publishing does on the computer what used to be done with scissors and glue and other non-computer methods - put together text and graphics for printing. High-end word processors can do much of what a desktop publishing program does, at least for fairly simple documents. The difference between Where you are: them has become a bit blurred. Look at a national magazine and try to duplicate the layout and graphics quality in a word processor! You will see that there IS a difference. For professional publications, a desktop publishing program gives the precise control needed and also advanced capacities such as preparing four-color separations for commercial printing.

Levels of Software "Desktop publishing" covers a wide range of activities and difficulty levels: 1. Professional Create for commercial printing - magazine, company annual report, newspaper, book, full-color advertising 2. Small business/home office Use a wizard or template to create a brochure, business card, or ad and print on your own printer 3.Specialty programs Make your own greeting cards, calendars, or labels. Print T-shirts. Major players in the desktop publishing game include Microsoft Publisher, Corel Ventura, QuarkXpress, and several Adobe products - PageMaker, FrameMaker, InDesign Purpose: To prepare documents with graphics with precise control of the layout Major Advantages: Ability to place text and graphics precisely on page Ability to chain sections together like newspaper columns Advanced tools for professional work Features/Terms: Layout - arranging text and graphics Clip art - pre-drawn pictures to add to page WYSIWYG - What You See Is What You Get pronounced "wiz-e-wig" How page displays on screen is the same as how it prints separations- For full color in high quality printing, the paper goes through the printing press 4 times, once for each of the colors cyan, magenta, yellow, and black (CMYK color system). The print shop must create separate versions of your document, called separations, for each color. 52


SPREADSHEET A spreadsheet is the application of choice for most documents that organize numbers, like budgets, financial statements, grade sheets, and sales records. A spreadsheet can perform simple or complex calculations on the numbers you enter in rows and columns. Examples of spreadsheet programs: MS Excel, Lotus 1-2-3, Quattro Pro, and Open Office Calc. Purpose: Organizing numbers Major Advantages: Can calculate for you using formulas Auto-update of related numbers when data changes Can display data in graphs and charts Features/Terms: Rows & columns - Creates a grid Cell- Intersection of row and column. Can contain text or numbers or a formula. Formula -Calculates value to put in cell, like a total, an average, interest amount, etc. =SUM(C21:C45) =Average(B3:W394) =.095*LoanTotal chart - Graphical representation of the data Do It! Would you like to see a spreadsheet at work? You can open an actual spreadsheet by clicking one of the icons in the first row below. Depending on your software, you will either get an Excel window or the spreadsheet will open in a new browser window which will have new toolbars and menu commands. If you do not have the software to actually open the spreadsheet, use the second set of links to open images that show how a spreadsheet looks. The images also open in a new window.

Look for the spreadsheet features listed above. [rows, columns, cells, formulas, and charts] Databases A database is a collection of data that you want to manage, rearrange, and add to later. It is a good program to use to manage lists that are not entirely numbers, such as addresses and phone numbers, inventories, and membership rosters. With a database you could sort the data by name or city or postal code or by any individual item of information recorded. You can create forms to enter or update or just display the data. You can create reports that show just the data you are interested in, like members who owe dues. Both spreadsheets and databases can be used to handle much the same information, but each is optimized to handle a different type most efficiently. The larger the number of records, the more important the differences are. Examples of databases: MS Access, dBase, FoxPro, Paradox, Approach, Oracle, Open Office Base. Purpose: Managing data Major Advantages: Can change way data is sorted and displayed Features/Terms: A flat database contains files which contain records which contain fields

53


A relational database contains tables which are linked together. Each table contains records which contain fields. A query can filter your records to show just the ones that meet certain criteria or to arrange them in a particular order.

Types of databases 1. Flat database: The earliest and simplest databases are flat databases. A flat database may still be all you need for your purpose. Advantages: Easy to set up Easy to understand Disadvantages: May require entering the same information in many records. A text database is hard to read. A single record in a spreadsheet database may not fit across the screen. A text database is a plain text file where the fields are separated by a particular character like a vertical bar | or a comma , or a semi-colon ; . The example below puts a vertical bar between each field. The first record shows the names of the fields. A text database is hard to read in this raw form. A database program can show each record separately in a more readable display. It is hard to create a report that contains just the parts you want to see.

A spreadsheet can work as a flat database. Each field is in a separate column and each row is a single record. The example below shows how quickly a record gets wider than the screen. You cannot use two rows for one record.

2. Relational database: Microsoft Access and Oracle and other relational databases are more advanced and more efficient. This kind of database uses a set of tables which are linked together. Using a well-designed relational database can greatly reduce the amount of data you must enter each time you add a record. For large numbers of records, a relational database can search through the records faster. Advantages: Reduces the duplication in data entry. Faster searches. Can create forms and reports that display only the data you want to see. Can create queries to answer questions that are hard or impossible to answer in flat databases. 54


Disadvantages: Can be complex to set up, using many tables. It is harder to understand how all the parts relate to each other. Below is an illustration of the tables in a small database that records information about insurance agents and policy holders. This particular insurance office works with several different insurance companies. There are 7 tables in the database. The lines show which fields in each table are the same. These link the tables together.

Each agent can be licensed with several different companies and in several different states. In a flat database you would have to have a record for each agent for every company and state he is licensed with, repeating the agent info for each record. If the agent moved to a new house, you would have many records to update with his new address. Argh! Too much typing!! With a relational database, there will be only one place to update. You can design a form so that you can do this all in one spot! This is much easier than repeating so much information for each record as you would do in a flat database. The images below show the two screens for the Agent Info Form. This form can be used for entering new agents as well as for displaying the current ones.

Queries You often want to look at just part of the data in a database. You can reorder or filter your data using Structural Query Language (SQL). You might want a list of people who have a particular postal code, for example. Happily there are visual methods you can use to create your query, like the example below from MS Access. You can drag the fields from the list at the top and drop them in the columns at the bottom. You can add sorting orders or criteria, like picking a particular postal code. The query below brings together the fields from the Agent Info table that is needed for mailing labels.

The actual SQL code for this query looks a lot different from the Design view above! No wonder a drag and-drop method was created.

GRAPHIC PROGRAMS Graphics programs deal with pictures, either static or moving, flat or 3D. There are an amazing number of different formats for images in the world and no one program can handle them all. Adobe Photoshop is the most widely used graphics program for professionals. PaintShopPro and Adobe PhotoShop Elements are popular with non-professionals because they offer most of Photoshop's features at a lower cost. There are many other programs that work with graphics. Some specialize in handling photographs or animations or creating logos. You can learn a lot by digging around a program's web site. Most include info about features plus how to lessons. 55


Purpose: To create and edit images Paint programs work with pictures on a pixel-by-pixel basis, where a pixel is the smallest dot on the screen. Such programs handle photographs and most clipart. MS Paint is this type of program. Advantages: Control over each dot in the picture Disadvantages: Angled lines are jagged stair steps, especially if enlarged. Drawing programs, on the other hand, define images in terms of vectors, that is, equations that describe geometric shapes. Fortunately, the user doesn't have to do the math! Drawing objects in MS Office are vector images. Advantages: Does not get as fuzzy or jagged when the size is changed. The file size is smaller. (For the web, the original vector picture at right had to be converted to a bitmap format.) Disadvantages: Can't change the color of a dot in the middle of a shape. Animation and video programs put a set of still pictures into a sequence. When the sequence of images is run, the change from one picture to the next fools the eye into seeing motion. This is how movies and television work. An individual image in an animation is called a cel. (Yes, there is just one l in that word!) The animation of eyes above was made with just 2 cels. The animation below from Microsoft GIF Animator takes 56 cels! Features/Terms - bitmap image a picture defined as a series of dots - vector image a picture defined as a set of geometric shapes, using equation - animation a sequence of images that are shown rapidly in succession, causing an impression of movement - pixel a single picture element, the smallest dot on the screen. A period (.) is made of 4 pixels in a square. - palette a set of choices, such as colors or shapes - brush a tool for drawing lines. May give the effect of using a pencil, a paint brush, an airbrush spray, chalk, charcoal, felt-tip marker... handles shapes on a selected object that allow you to change the shape by dragging the handle - fill colors an enclosed area with one color or pattern - cel a single image in an animation sequence PRESENTATION PROGRAM A presentation program, also known as presentation graphics, links together a sequence of slides containing text and graphics. A slide show might be used for a sales presentation or for training or to enhance any kind of speech. A presentation program includes a number of tools for creating graphics that are quite useful. High-end programs can add sound and video to the slides.

Examples of presentation software: Microsoft PowerPoint, Corel Presentations, Lotus Freelance Graphics, Harvard Graphics, Open Office Impress Purpose: Turning information into visual form Major Advantages: Pictures convey info faster than tables of numbers. Having something to look at helps keep your audience focused on what you are saying

56


Slide show: The whole sequence of slides shown in order Transition effect : The way a slide changes to the next slide. For example the new slide might appear to slide in from the side over the old slide. Animation effect: The way part of a slide appears. For example, a line of text might be revealed one letter at a time. Example of a Presentation The slides that make up the presentation Chap1.ppt are shown below. This presentation was written in 1996 as a part of a review for students. There are 10 slides, but the slides are revealed in parts. When you actually go through the presentation, it takes 1 click to change to a new slide or to reveal a new part of a slide.

Do It! You can experience the slide show right here! The inline frame below will be your viewing screen. Detailed directions are below the inline frame. COMMUNICATIONS These programs temporarily connect computers to each other to exchange information. They may use telephone lines or dedicated cables for the connection. This allows you, for example, to work at home on the weekend and transfer all you've done to your computer at work before you leave home. These are not the same as networking programs where computers are actually linked together all the time. Most communications programs now include many different communication functions in one interface. Purpose: Transmitting data and messages between computers Major Advantage: Speed & convenience A communications program includes one or more of the following actions:  sending and receiving files: FTP (File Transfer Protocol)  exchanging messages in a group: chat programs  private text messages: instant messaging  voice messages  video conferencing  phone calls over the Internet, like Skype FTP (File Transfer Protocol) An FTP program manages the moving of files between computers. When you download a file over the Internet, you are using an FTP program. Some programs like word processors and HTML editors include this ability to upload files to web sites without having to use another program. The image below is for the program FileZilla that I use, which is a fairly typical FTP program. It shows the folder tree for both the source and destination. You can copy in either direction, in this case by dragging the files or folders from one list and dropping where you want them, just like in Windows Explorer. And, it is free!

57


Chat In a chat program you join a chat room. You write messages that appear in a window that shows all the messages being sent in this chat room. Everyone who is logged in to this room can read your messages. The image below is for the program mIRC. Each person listed on the right is "in" the room and can write messages and all the others can read them. Recent chat programs let users format their text with color and even with different fonts. People in chat rooms tend to use a lot of abbreviations and smiley faces.

Instant Messaging An instant messaging program notifies you when your friends are online. Then you can send them messages, which they see immediately. Only the one you send the message to can see it and only you can see the messages that are sent to you, unless you choose to change to a multiple-user mode. Recent versions of instant messaging include the ability to use video conferencing, to play games together with your friends, and even to make phone calls over the Internet. Examples of instant messaging programs are ICQ, AOL Instant Messenger, Yahoo! Messenger, Google Talk, Facebook, and Windows Live Messenger. The image below shows what such messages look like in a chat in Facebook. You type your next comment in the text box at the bottom. The Facebook profile picture for the person 'talking' shows at the left.

Browser An Internet browser is a program that lets you navigate the World Wide Web or view HTML pages on a CD or DVD or on your hard disk. [It's what you are using to view this page on the computer!] A browser displays web pages, keeps track of where you've been, and remembers the places you want to return to. More information is available over the Internet every day, and more tasks can be done. You can buy books, check on your bank account, buy and sell stocks, even order pizza over the Internet. But you have to have a browser to do it. Internet Explorer remains the most popular browser, though it is losing ground. Mozilla FireFox has evolved from the original favorite browser, Netscape, and has become the favorite of many. Google's Chrome is gaining market share. Safari is the browser that comes with Apple computers. Modern browsers include many of the same features such as tabs instead of separate windows to make it easy to move between several open pages, a list of previously viewed pages (History), a list of places you want to be able to get back to (Favorites), the ability to install add-in programs to view videos in various formats or interact with web pages. Browsers that are built into devices such as smart phones may be unique to the manufacturer or they may be simplified versions of browsers.

Purpose: Navigating the Internet 58


Major Advantage: Can display graphics, which older internet applications didn't Keeps a list of places you want to return to. Shows HTML pages, which can include links to other pages and files for quick access. There is quite a difference in popularity of browsers over time and depending on what equipment you are using to browse. The pie charts below are from Sept. 15, 2011. The market share on the desktop computers for Microsoft Internet Explorer dropped 6% while Google Chrome's share went up 7.27%. Netscape used to be the dominant browser and is now less than 1% of users! Now that's a fall! For mobile computers like smart phones and for tablets, the dominant browser has clearly been Safari on Apple products like the iPhone and iPad, but its market share is dropping. Most of the other browsers gained in this market. Web Pages To create a web page for the Internet, you must write HTML (Hypertext Markup Language) code to define what is on the page, create or acquire the images for the page, and then upload the files to a web server. What do you need?  HTML editing program  Graphics editing program  Uploading program  Browser  Web space HTML Editor: You can use any plain text editor, like Notepad, to write the code. Or, you can use a specialty program for writing HTML pages. Such programs make it much easier to manage complex pages and large web sites. Also useful are programs that help you write scripts or that check your HTML code for errors. Popular programs for writing HTML include Notepad (write the code yourself!), Microsoft Expression Web, and Macromedia Dreamweaver. Graphics: For the images on your web pages you need a graphics program that can save your images in GIF or JPG format. PNG format will work for newer browsers, but GIF and JPG work for all browsers. MS Paint: Older versions of MS Paint, which comes with Windows, cannot save images in GIF, JPG or PNG formats. Can your version? Open MS Paint (Start menu > Run > type mspaint and click OK). Look in the Save As dialog at the file types: File > Save As > File type list. If the list includes GIF and JPG, you are ready to create and edit images for your web pages. (If you do much with images, you will soon want a more advanced program than MSPaint!) You might also want a scanner to scan photos and drawings. Collections of clip art come in very handy. Uploading: To move your new web pages and images to a web server, you need uploading software, such as an FTP program. HTML editors like Expression Web and Dreamweaver include uploading as a built-in feature. Browser: To view your web pages you need a browser, like Internet Explorer, FireFox, Google Chrome, Safari, or Opera. Web space: You can view pages yourself that you save to your hard disk, but no one else can see them. You need access to space on a web server to share your work with others on the Web. Your ISP account, with which you connect to the Internet, may come with some web space. There are ad-based, free web hosting accounts. Or, you can purchase a web hosting account with a commercial hosting service. HTML Code When each logical part of a web page is marked, the browser will know how to display the contents in a way that makes sense for the particular display device and user. Special code tags are used to mark all the parts of a web page. For example the text in an ordinary paragraph is written in between opening and closing tags like this: <p>This is a paragraph</p> Example 59


In the frame below is a simple web page. Click the link below it to view the source code for the page. Can you find the tags that define the two headings and the list items? How about a simple paragraph? What does the image tag contain? What line dictates the background image? Your browser does not support inline frames or is currently configured not to display inline frames. View example page View source code View source View page Learning more Reading and analyzing the source code for the pages you see on the Web is a good way to learn about writing web pages. You can view the source code for any page that you can view with your browser. Try it with this page. Right click on the page (not on a link or an imag. A context menu appears. Select View Source or View page source or similar command. The source code will open in a text editor or in the browser, depending on your browser. The code for this page is a lot more complex than the example above! Email Email, or electronic mail, is becoming more and more popular as people learn to communicate again with written words. For many purposes it is superior to a phone call because you don't have to catch the person in and you can get straight to the point. No time is wasted on casual conversation. It also leaves a written record to refer back to for a response or if you forget who said what. Email is superior to the traditional office memo because it uses no paper (Save the trees!!) and it can be sent to a whole list of people instantly. An email client is the program that has to be on your computer to download and manage emails. Commonly used email client programs include Microsoft Outlook, Windows Live Mail, Mozilla Thunderbird, and Eudora. Another way to handle email is with a web-based email account. Your email is managed entirely through web pages. Your computer needs only a browser to access email, compose new messages, and to reply to messages. HotMail from MSN, Yahoo Mail, and Gmail from Google are popular web-based email sites.

Purpose: Transmitting messages between computer users Major Advantage: Speed Can send copies to several people at once Major Disadvantage: You don't know if the receiver actually reads it, though you can find out if they received it. Of course in a phone conversation you don't really know if the person is actually listening either! With no body language or vocal intonations it is difficult to convey the emotional tone you want. Irony and sarcasm are particularly dangerous since your reader may take you seriously. Security & Utility Programs There are many programs or combinations of programs that can help keep the bad guys from messing with your computer and its data. We can call this category of program Security Programs. Security software is one of the categories of special purpose programs we can group together as Utility Programs. Some of these just tweak the user interface and some perform highly technical tasks. To do a good job of keeping your computer safe from random visitors or from crime syndicates, you need several types of programs. Types of security programs: ď&#x201A;ˇ Anti-virus: Continuously watches for incoming attacks. Scans regularly for hidden malware. Repairs many kinds of damage. ď&#x201A;ˇ Firewall: Controls who gets into your computer from the Internet ď&#x201A;ˇ Anti-spam: Examines incoming email and sends known or suspected bad messages to a special folder, Spam or Junk. 60


Purpose: To avoid or repair damage from malware (a virus, trojan, worm or other intrusive software) Major Advantage: Protection is easier than recovering from a malware disaster Major Disadvantage: Must be configured correctly to work effectively. Must be updated regularly with new virus definitions. Examples of security programs, some of which include several programs: Norton Security Suite, Microsoft Defender, Avira Antivirus, Windows Firewall, Norton 360, Trend Micro Internet Security Plus, Zone Alarm.

Utility Programs There are many categories of utility programs, including security software. What is counted as a utility program depends on who is doing the counting! The usual definition is that a utility program not application software that the user uses to create a document or image or to play a game or to surf the web. It does something to way the computer looks or behaves, often in the background. [Some websites that sell software include a lot more in their Utility category, including games(!), money management software, genealogy software, course management software, and many more.] Purpose: To customize the way the computer behaves, making it more efficient or easier or safer to use. Major Advantage: Better features or better user interface than what comes with the operating system. Special features for keeping your computer running well. Configuring your computer to suit the way you work. Major Disadvantage: Many are very technical and require some expertise to use. Examples: Parental control programs block access (especially for children) to web sites that are not suitable or are more likely to result in malware attacks - NetNanny, K9 Web Protection, some operating systems include some features. 1) Encryption programs encode your data so that to read it the user must have the right key code. Some operating systems include some type of encryption. Could be for the whole disk, selected folders, or selected files. 2) Password management software remembers all of your logon and password information so that you only have to remember how to get into the password software - one thing! The file that records your passwords is encrypted. - Password Safe, Roboform. 3) Back-up software can automatically save a copy of your data or the whole computer's contents to DVDs, tape, or to a data site online. To be prepared in case a disaster happens, whether it is a security issue or a dead hard drive issue, you need a back-up copy of your important data. - Windows Disk Defragmenter, Norton SpeedDisk. 4) Disk defragmenting software rearranges files so that all parts of the file are next to each other. The computer will scatter pieces of a file all over the disk, wherever there is some room. Defragmenting makes it easier for the computer to find and display the file. PIM PROGRAMS (PERSONAL INFORMATION MANAGEMENT) PIM programs (Personal Information Management) are a special kind of database. A PIM will normally include an address book, a calendar to schedule activities and appointments, and a to-do list where you list chores, calls to make, various things to do. Some popular programs which include PIM functions are Microsoft Office Outlook, Lotus Organizer, Windows Calendar and Windows Contact List, Google Calendar and Google Notebook, Palm Desktop, Novell Groupwise. New versions of these programs add email management, wireless access, and other features for the new, hot technologies. The new goal for a PIM seems to be to vanish into the background, while letting you have access to your email, calendar, and scheduling software from anywhere. Purpose: Tracking personal information like- appointments ,address book ,birthdays,phone messages, notes on future projects Major Advantage: Quick access to schedule data and address book. Can often be merged into documents directly. Contact Manager An advanced PIM may be called a Contact Manager. Such a program is optimized to make it easy to track who you have talked to or met with and what you did or said. A contact manager automatically links a name in the address book to names in the calendar. Clicking on the name in the calendar brings up the full contact information, including fields for notes about what you did and reminders for what you need to do after the meeting or conversation. From the address book you can bring up a list of when you had contacts with this person. Powerful stuff! 61


Integrated software combines the functions of several programs into one interface. Such a program is usually designed for the beginning or casual user. Many advanced features are omitted that might be found in stand-alone products. For example, the word processor in an integrated software package would not likely have a way to automatically generate a table of contents and would have fewer options on how to handle footnotes, headers, and footers. Microsoft Works is an example of integrated software. SUITES :A software suite is a set of applications which can each stand alone. They are packaged together for a lower price than if all were bought separately. There are usually enhancements that help the applications communicate with each other, also. Some popular suites of office software include MS Office, Lotus Smart Suite, WordPerfect Office, Open Office, and iWork (for Mac computers). These include several programs, such as:  word processing  spreadsheet  presentations  e-mail client  address book  database Other Examples of Software Suites An example of a graphics suite is Corel Draw Suite, which includes programs for:  vector illustration layout  bitmap creation  image-editing  painting  animation software An example of a publishing suite is Adobe Publishing Collections, which includes:  Adobe PageMaker - desktop publishing  Adobe Photoshop - bitmap graphics  Adobe Illustrator - vector graphics Adobe Acrobat - converts documents to Portable Document Format for sharing Purpose: Linking different applications together for better work (integrated software) Simplifying things for new users Major Advantage: Costs less than a set of similar stand alone applications bought separately Major Disadvantage: (integrated software) Lacks many features of the stand-alone versions of the same software. (suites) You may not need all the parts or the advanced features in the collection. Questions and Answer 1. The software application that is used most often is called ? Ans: Word Processing 2. The largest, fastest, most expensive type of computer is called? Ans: Super Computer 3. A computer which links several PCs together in a network is called? Ans: The server 4. Name the application that is used when you want to publish a magazine? Ans: Desktop Publishing 5. Julian is a sales rep calling on up to 20 businesses a week. To keep track of his appointments and his clients' addresses and phone numbers, he should use a ? Ans: Personal Information Manager 6. Acme Corp. sells 1000 different products to over 20,000 customers. To record the sales and shipments they would use a ? Ans: A database 62


7. A single application that combines the major features of several types of applications is called? Ans: Suite 8. Using a word processor you can change the following Ans: Typeset,Font and Size,size of margins,Space between lines, 9. Input, processing, output and storage are the steps in the Ans: Data Processing Cycle 10. GUI stands for ? Ans: Graphic User Interface CHAPTER 7 DIGITAL SYSTEMS INTRODUCTION At the present time, there exists many digital systems used to represent numerical values, among which the decimal system used by human beings to carry out their calculations, the binary and the hexadecimal system used by computers to store and process data. As values manipulated by human are represented in the decimal system, they cannot be directly process by the computer as it uses different systems ( the binary and the hexadecimal system). Therefore, an operation called conversion is usually used to convert decimal numbers into their binary representation and vice-versa as well as conversion of binary numbers into hexadecimal numbers and vice versa. 7.1 CONVERSION BETWEEN THE BINARY AND THE HEXADECIMAL SYSTEM Method: To convert a binary number B to hexadecimal, we divide B into several partitions from the right to the left, each of them having four symbols . After doing this, we replace each partitions of four symbols with its hexadecimal correspondence using Table 1 below. Decimal Binary hexadecimal decimal binary hexadecimal Decimal binary hexidecimal 0 0000 1 4 0100 4 8 1000 8 1 0001 1 5 0101 5 9 1001 9 2 0010 2 6 0110 6 10 1010 A 3 0011 3 3 0111 7 11 1011 B decimal Binary hexadecimal decimal binary hexadecimal Decimal 12 13

Binary 1100 1101

hexadecimal decimal C 14 D 15

binary 1110 1111

hexadecimal Decimal E F

decimal

Binary

hexadecimal decimal

binary

hexadecimal

binary

hexidecimal

Notice: when cutting up B, if the remaining symbols no longer attain four, we have to add some zeros at the beginning of B for the partition to be made up of four symbols. Example: convert the binary number (0010000100001110)2 to hexadecimal, Solutions: (1110)2 = (E)16 (0000)2=(0)16, (0001)2=(1)16,(0010)2=(2)16 so, (0010000100001110)2= (012E) 16 7.2 â&#x20AC;&#x201C; HEXADECIMAL-BINARY CONVERSION Method: to convert a hexadecimal number H to binary, we just need to replace each hexadecimal symbol of H its binary correspondence. Example: convert the hexadecimal number (2102)h to binary 63


Solutions: from the table 1, (2)16=(0010)2, (1)16=(0000)2, (2)16=(0010)2, So, (2102)16=(0010000100000010)2 7.3- CONVERSION BETWEEN THE DECIMAL AND THE HEXADECIMAL SYSTEMS 7.3-1 DECIMAL-HEXADECIMAL CONVERSION Method: to convert any decimal number N to binary, we proceed as follows:  We successfully divide N by 16 until we obtain a reminder that is less than 16  The results of the conversion divisions made starting from the last remainder to the last one Notice: Each remainder greater than 9 must be replaced by its hexadecimal correspondent in the table 1. Example: convert the decimal number (180)10 to hexadecimal Solutions: The procedure is consigned in the table below N 180

QUOTIENT 4

REMAINDER 11

B

As (11)10= (B) 16, and (4)10= (4)16, we obtain (180)10= (b4)16 7.3-2 DECIMAL-HEXADECIMAL CONVERSION Method: To convert any binary number B to decimal, we proceed as follows:  Define the position of each symbol within B starting from the right, beginning from zero.  Multiply each symbol with the value of its position  Sum the obtained values of each multiplication to obtain the result of the conversion Example: convert the hexadecimal number (4BBA) 16 to decimal Method: 3210 4BBA

Position

(4BBA)16 = (10*160)+(11*161)+(11*162)+(4*163) =(10*1)+(11*16)+(11*256)+(4*4096) =10+176+2816+16384 =(19386)10 So, (4BBA)16 = (19386)10

7.4 – BINARY SYSTEM OPERATION 64


7-4.1 â&#x20AC;&#x201C; ADDITION Method: To add two binary numbers , we used these rules: 0+0 result = 0, deduction = 0 0+1 result = 1, deduction = 1 1+0 result = 1, deduction = 0, 1 + 1 result=0,deduction = 1 Example: add (01101)2 and (01110)2 Solution: 01101 01110 1100 11011

deduction result

7-4.2 - SUBTRACTION Method : to subtract two binary numbers, we use these rules: 0 - 0 result = 0 , deduction = 0 0 - 1 result = 1, deduction = 1 1 - 0 result = 1, deduction = 0 1-1 result = 0 , deduction = 0 Example: subtract (01101)2 from (01111)2 Solution: 01111 01101 0001 00001

deduction result

Conclusion The conversion between numbers from different bases as well as the arithmetic operations in the binary system some of the operations that are carried out by the computer during data processing.This lesson has shown how you can carry out these operations in other to have an idea of how the computer computes data.

65


GENERAL QUESTIONS 1. Define electronic data processing? - The conversion of raw facts into information by the combination of hardware and software 2. Differentiate between Data and Information? - Data are raw facts while information are facts that have been converted to have meaning . 3. How is Data organized in a computer system? - Data are organized in files 4. Give two examples of a file extension and state the application involved? -.Doc – microsoft word documents - .xls- microsoft excel - . Ppt – microsoft powerpoint -.pdf – portable data format documents 5. Give the steps in which data is captured and process during a National Census? - Collection of information by agents - input into a system - analysed and processed - output via print out etc. 6. Give any two elements of data processing? - Input(keyboards,microphones) -processing(cpu) -storage(hard drives,cd,dvd) -output(monitors,projectors..) 7. What is batch processing? - Processing of large amounts of information at once 8. What can be done in order to recover a lost file or document when your computer crashes - Always backup your files on external storage or burn them on cd/dvd 9. What are the differences between Information and Communication? Information is data that has been processed to have meaning while communication is the medium by which information flows from one point to another. 10. How many Bits are there in 4kb? 11. Why are computers linked together? To share resources such as printers, hard drives,cd/dvd….printers etc. 12. Define a network Architecture Simply the design of a network e.g. LAN (LOCAL AREA NETWORK) WAN (WIDE AREA NETWORK) AND MAN (METROPOLITAN AREA NETWORK) 13. Define a network Topology? Simply the arrangement of a network e.g. Star network which is arranged in a star-like manner, Bus topology, Ring Topology and Hybrid Topology which is a combination of the different topologies. 14. Differentiate between a Star Topology and a Bus Topology? Star-like , arranged like a Bus seats, information flow from a central point in a star toplogy while in a Bus topology it flows from node to node. 15. Give an Example of a Star Topology in reality? Client-Server Design where you have a central server ,and clients connects via switch to the server . 16. What is a Communication Medium? Passage way for information e.g air, water,cables etc. 17. List two means of communication you know -Wireless communication -Wired Communication 18. How does is information process by a computer?

66


Binary(1s and 0’s ), information has to be transformed into computer language before its processed by CPU 19. Define the following, a) Database Container well structured information that can be shared, accessed at any time b) Database Management Systems - Software programs capable of creating and managing databases c) A file A collection of related information e.g. student’s file in a school d) A record logically connected set of one or more fields that describe a person,place or thing e) A field A character or group of characters (alphabetic or numeric) 20. Give three examples of a database. - MSACCESS,MYSQL,MSSQL,ORACLE DATABASE 21. Differentiate between a Relational and a Flat Database? Tables have relationships in a RDMS such as msaccess while in a Flat database information are not related e.g. Excel 22. Differentiate between a multi-user and Single User database. - Multiple users can work on the database at the same time while in a single user database , just a single person can work on the database at particular time. 23. How is Data stored in a Database? - Data is stored in tables 24. The link between Database tables is called? - Relationships 25. The method in which information harnessed from one or several database tables is called? - Queries which can be Inner Join, Outer Join etc. 26. What is a Computer Software? - The information that the computer uses to get a job done 27. Differentiate between Computer Software and Hardware. Programs and instructions/tangible parts that functions together 28. What is an Application? Specialized programs used by a computer to carry on basic functions such as Accounting, examples include Le Sage, QuickBooks etc. 29. What is a Utility Program? Specialized programs that help other programs to function properly e.g. Winzip, Winrar, AntiViruses etc. 30. Give two examples of Utility Programs. - Winzip,Winrar,PDF Reader,AntiViruses etc 31. Give two examples of Application programs - Le Sage, Quickbooks, 32. What is a Software Package? Same thing as Software Suite 33. What is Software Suite? A software suite is a set of applications which can each stand alone e.g. Microsoft Office which include MSWORD,MSACCESS,MSPOWERPOINT etc. 34. Define an Give an Example of the following; a) Presentation Programs – Microsoft PowerPoint b) Spreadsheet Programs - MS Excel c) Word Processing Programs-MS Word d) Graphic Programs-Microsoft Paint e) Video editing Programs- Adobe After effects,Video Studio etc. f) Internet Browsers – Mozilla Firefox, Opera,Internet Explorer, CometBird etc. 35. Define an Operating System? An OS is a set of programs that controls how the hardware of a computer works… It is the means of communication between the user and the computer, deals with the loading and running of application programs and manages the transfer of data and files to and from the peripheral devices 36. Give four examples of an Operating System (OS)? - Linux, Unix, Windows, MAC OX etc. 37. Give the main functions of an Operating System • Accepts data from input devices and transfers it to the computer’s memory. • Makes sure any output is sent to the correct output device. • Manages the transfer of data between the computer’s memory and backing storage devices. • Provides a human computer interface for the user

67


• Provides special facilities for multiprogramming. • Manages system security by restricting access to prevent unauthorised access to the system. • Provides a human computer interface for the user • Provides special facilities for multiprogramming. • Manages system security by restricting access to prevent unauthorised access to the system. 35. What is GUI? -Graphic User Interface 36. Give the advantages’ of a GUI to the user 37. Give the full meaning of the following terms: a) RAM – Random access memory (Volatile Memory) b) ROM – Read only memory (information cannot altered, except for programmable read only memory) c) CMOS - Complementary Metal Oxide Semiconductor (controls date and time and other functions) d) DOS – Disk Operating System e) MSDOS- Microsoft Disk Operating System f) POST-Power onself test g) CPU- Central Processing Unit 38. Why is the CPU considered the heart of the of the Computer and gives the basic components to support your answer. Because its process all information that enters the computer It contains the ALU( ARITHMETHIC AND LOGIC UNIT for the processing of logics and maths, the CU(CONTROL UNIT that controls the way information is processed by the CPU and the memory that stores information to be processed or that has been processed and pass on to the random access memory or hard disk to be stored. 39. Differentiate between an Input Device and Output Device Sends information into the computer via Keyboards,Microphones,scanners etc./ send out information to be printed by the printer or viewed on the computer monitor. 40. What is a Computer Peripheral and give three examples. The tangible parts that make up a computer e.g mouse, keyboards, case etc. 41. The three Main tasks of a RAM are: - Encoding or registration (receiving, processing and combining of received information) - Storage (creation of a permanent record of the encoded information) - Retrieval, recall or recollection (calling back the stored information in response to some cue for use in a process or activity) 42. Three main categories of hardware are; - Input - Output - Storage 43. The Unit of measurement of a Processor ? - Megahertz(1000000) and Gigahertz(1000000000) 44. What is the prime importance of a Computer Motherboard? - A motherboard is the central printed circuit board in many modern computers and holds many of the crucial components of the system, , providing connectors for other peripherals. 45. What is the difference between a Volatile Memory otherwise called Primary storage device and a Non Volatile Memory otherwise called a Secondary storage device ? - Volatile memory, also known as volatile storage, is computer memory that requires power to maintain the stored information, in other words it needs power to reach the computer memory. Volatile memory retains the information as long as power supply is on, but when power supply is off or interrupted the stored memory is lost; unlike non-volatile memory which does not require a maintained power supply. It has been less popularly known as temporary memory 45. What are the advantages of a networked Computer to a standalone Computer System? - With a network computer system , printers,hard drives etc can be shared amongst large group of system without necessary connecting these devices to those individual system. Secondly with a network system, information can be shared or send to groups of computer at the same time … Thirdly with a network system updates are easy as it can be dessiminated to all the other systems at once hence time and cost reduced. 46. Differentiate between a root folder and a Sub folder giving examples of each. - A Root folder is the main folder that holds other folders and sub folders of the system e.g C: / While a sub folder is a folder that is found inside another folder e.g C:/Barr 47. Give five examples of any free web browser you know ? - Opera Mini, Mozilla Firefox, Cometbird, Google Chrome 48. Give two examples of an Instant Chat Messenger ? - Yahoo Messenger and Facebook Messenger….Windows live messenger, facetime messenger in MAC 49. Give two examples of a Free Spreadsheet program ? - Open Office Spreadsheet (CALC) ,Google Doc Spreadsheets, 50. Two Basic Functions of the Operating system are? Manage the computer's resources, such as the central processing unit, memory, disk drives, and printers.

68


Establish a user interface. Execute and provide services for applications software. 51. What are the functions of a Graphic User Interface? - Permits you to select icons for easy UI management Permits you to sort and shuffle things around Have shortcuts to easily assessed programs on your desktop. 52. What is an information System? Hardware and Software working together, by taking data that has been input and convert it into information./ an information system processes data to produce information. 53. What is a Multitasking OS? A Multitasking OS allows two or more programs to run at the same time. E.g like having MS Word,iTunes and solitaire open on your computer at the same time. 54. What is a Multiuser OS? A Multiuser OS allows many different users at different terminals (in a network) to share the processing time on a central computer. 55. What is a Network Bandwidth? It is the rate at which data can be transmitted down the communications line in a given period of time… 56. What is the full meaning of the following terms a) Internet : Inter network ( network of computers capable of sharing resources such as files,messages.. b) Intranet: Intra network( network of computers which are local) e.g. a school network c) ISP: Internet Service Provider d) www: World Wide Web 57. Define A Network Protocol and give two examples ? Sets of rules that control the exchange of information in a network e.g. HTTP( Hypertext transfer protocol used by web browsers, TCP/IP( transmission control protocol and internet protocol. 58. Give two examples of a network Operating System? - Windows XP and Windows Server 2000 59. Give two Examples of Windows System Files ? - Config.sys for system configurations - Autoexec.bat for autorun programs 60. Give the DOS command to create a directory? - MD – make directory will create a new folder 61. What makes a File server so Powerful? - Large amount of RAMS and hard disk - Holds the network OS - Holds application software such as Microsoft Office Suite - Stores user files created on the system 62. What is the prime function of network card? - Permits Communicates with other computers in the network 67. Give two examples of network cables you know ? - UTP (UNSHIELDED TWISTED PAIR ) AND TCP(SHIELDED TWISTED PAIR), COAXIAL,OPTIC FIBRES 68. What is the full meaning of MODEM? - It stands for Modulation and Demodulation 69. Give the advantage of a hard disk over a diskette - Hard disk has larger storage capacity than Diskettes - Higher read and write speeds than Diskettes 70. Why are so many MicroComputers today have hard disks? - can be move easily - Inexpensive -very high storage capacities 71. What is the full meaning of BIOS and is it a ROM - Basic input and output system, it is a ROM and a non-volatile memory 72. What is a Cache Memory? Cache memory is extremely fast memory that is built into a computer’s central processing unit (CPU), or located next to it on a separate chip. The CPU uses memory to store instructions that are repeatedly required to run programs, improving overall system speed. 73. What do the following acronyms stand for? a) CPU – CENTRAL PROCESSING UNIT b) ALU – Arithmethic and Logic Unit c) MB-Megabyte 74. Name three printers and give an advantage - Dot Matrix – Cheaper to buy and run compared to other printers. - Ink Jet Printer – Quieter to print than a dot-matrix.

69


- Laser Printer – Prints more pages per minute than the Ink Jet Printer. 75. What do the following acronyms mean? ASCII: American Standard Code Information Interchange VDU: Visual Display Unit DVD: Digital Versatile Disk CPS: Characters Per Second PPM: Pages Per Minute DPI: Dots Per Inch WORM: Write Once Read Many 76. What is the Memory Capacity of the following ? A) CD ROM – 700 – 800MB B)DVD – 4.7 GB C)FLOPPY DISK – 1.44MB D) ZIP DISK – 100MB 77. What are the four features of a GUI? -Windows -icons -menus -pointers 78. What is full meaning of HTML Hypertext markup language, use to program web pages 79. What is the difference between hacking and scamming? Hacking is the illegal infiltration into a computer system while scamming is ripping off an individual pretending to be someone you are not . 80. What are Computer Viruses ? These are malicious programs that are capable of replicating and destroying other computer programs and even hardware. 81. Convert 3FE16 to a decimal number . 82. Give an Example of a PIM - Personal Information management includes Office Outlook,Lotus Manager,Windows Calendar etc 84. Give an example of four Types of security programs you know ?  Anti-virus: Continuously watches for incoming attacks. Scans regularly for hidden malware. Repairs many kinds of damage.  Firewall: Controls who gets into your computer from the Internet  Anti-spam: Examines incoming email and sends known or suspected bad messages to a special folder, Spam or Junk. 85. Give two types of programming languages you know ? - Java and C 86. Group Computers according to their categories and speed. - Mainframe Computer ,Super Computer,MicroComputer and MiniComputer 87. What is the difference between a soft copy and a hard copy document ? - Soft copy is output via the monitor or projector while hardcopy documents are documents that have been printed a paper or burn on disk. 88. Apart of a computer give an example of an electronic device capable of processing,storing and displaying data? - A Calculator 89. Give two examples of a free Operating System? - Ubuntu - Mandriva 90. Give an example of a Phone Operating System? - Symbian, - Windows Mobile - OSX for Apple IPhones 91. What is a data center? - It a center for information exchange and processing 92. What element in the computer is responsible in cooling down the CPU? - The System Fan 93. What does Cloud Computing means? - Computers connected to the internet. 94. What is a Workgroup? These are specified users on a network with a common subject matter e.g. Teachers Workgroup, Students WG etc. 95. Give the main source of information in banking environment - Via customers service 96. What is the difference between electronic data processing and Data processing? 97. Give the most important element of an IS on which all other elements rely on 98. Define the following terms

70


a) File b) Record c) Field d) Database 99. What is the relationship between a CPU and a Random Access Memory? 100. Differentiate between Database and a Database Management System?

71


Data processing for technical schools