Operating Systems When you turn on a PC or Mac the electricity starts-up a program (Boot File) based in a ROM chip which searches the attached storage devices (usually the Floppy Disc Drive, then the CD-ROM drive and then the Hard disc drive) for a program called the Operating System., which it then loads into RAM memory. The Operating System is a suite of programs that controls the hardware and software running on the computer, allowing the user to communicate with application programs and peripheral devices. Whether you load or save a file, access the internet, print a hard copy or just type on the keyboard, the operating system is involved working in the background. These programs remain in RAM until you turn your computer off. STANDARD FUNCTIONS An easy way of thinking what an operating system does is to think about the tasks that can be done on the desktop of your computer. These are all tasks carried out by the operating system. Operating systems have a number of Standard functions including Memory management Controls where programs and data are stored in the RAM. It allocates suitable memory locations to programs and data and makes sure that they don’t get mixed up. File Management The operating system manages all the files that are located on backing storage. It is responsible for • Deleting, copying, creating and re-naming Files • Keeping the physical information as to where files are stored. • Formatting and Cataloging Discs • Loading and Saving to/from Disc • Ensures data is sent to the correct program • Controlling access to files (read and write privileges) Input / Output Reads information from the mouse and keyboard and reacts accordingly. Sends information to the correct printer. Error Reporting Sends messages to the user if there is a problem e.g. “out of memory” Interpreting user’s commands This is the connection between the user and the computer. It makes sure that the commands are valid and then translates them into instructions that the computer system can follow. We call this the Human Computer Interface (HCI). There are two main types of HCI • WIMP interfaces such as Windows 95 and the Mac-OS • Command Driven interfaces such as Unix and the Acorn MOS If a computer system is to be user-friendly it must have an easy to use interface, on the other hand it must be fast and flexible for the advanced user. • Command Driven Interface This is when all the functions of the package (Word processor, Database, etc.) are controlled by commands e.g. PRINT, SCREEN, and SAVE etc. This is not a very suitable environment for non-experts but means that an expert user can move quickly and easily to the point they want without having to take time going through numerous menus. VIEW is an example of a command driven word processor.
Int 2 Computer Systems - Comp Software
Information Sheet 5.4.1
Produced by P W Shadbolt Queensferry High School 2004
Operating Systems • WIMP (Windows, Icons, Menu and Pointer) This environment is said to be the most "user friendly". This means that beginners can learn how to use the system faster than other types of environment. The pull-down menus allows functions to be easily available and have the advantage over menu-driven environments of not passing you from one menu to another because all menus are available at all times. While having this ease of use for beginners the WIMP environment also allows expert users to use command keys to access functions quickly. Some micros even give you the opportunity to give a number of instructions with one command WINDOW This is an area of the screen that is used to display the document that the user is currently working on. Most systems can have several windows open at the same time, although only one is active at any time. You activate the window by using the pointer. ICONS These are small graphics that are used to represent items such as files, printers, disk drives etc. They help to make the operating system very user friendly. MENU This offers you a list of choices. The menu bar either at the top or bottom of the page will give you a list of choices, which you can select from. POINTER The pointer is an icon that is moved around the screen by using the mouse or other input device. The pointer is used to select from menus, select icons or make windows. STANDARD OPERATING SYSTEMS These are Operating Systems that are used by a number of different hardware manufacturers. The main advantage for the hardware companies is that users feel at ease with an Operating System they have used before; also there are many similar applications available due to the large market. There can be problems with a file that has been created by the same application package but used with different operating systems (e.g., Claris files created on the Mac are slightly different from those saved on the PC although they can be accessed from the application) ROM BASED OR DISC BASED Most computer systems like the Macs and PCs have their Operating Systems on disc (Disc Operating System). Some older systems like the BBC have their Operating Systems on ROM inside the computer. The advantage of the ROM based OS is that it works faster. This is because access to ROM is faster than access to disc or hard disc drive. The disadvantage is that in order to upgrade or improve your Operating System you have to take the computer apart to replace the chip. With the increase in access speed of hard disc drives there are very few computers left that have ROM based operating systems.
A DOS Window:
There are four main types of operating systems in popular use today: MS-DOS, Windows, UNIX and MacOS. All four of these operating systems run on personal computers. Examples of operating systems DOS is an old (early 1980s) command-line operating system that requires the user to memorise and enter all commands from a command prompt.
Int 2 Computer Systems - Comp Software
Information Sheet 5.4.1
Produced by P W Shadbolt Queensferry High School 2004
Operating Systems Windows 3.1 (late 1980s) was Microsoft’s first attempt at a Macintosh-like Graphical User Interface (GUI); this interface allowed: 1. programs to be launched by double-clicking icons with a mouse 2. files to be copied by drag and drop 3. much easier copy and paste. Windows 95/98/ME/2000/NT/XP are a family of Microsoft 32-bit operating systems. At the time of this writing these operating systems dominate the market and are to be found on most people’s personal computers. Microsoft has come a long way since Windows 3.1 and Windows has become much more powerful and stable.
OS2 began as a joint venture between IBM and Microsoft. IBM finished and marketed this operating system. It is not used extensively today.
UNIX was originally a command-line based operating system like DOS (although it predates DOS by more than a decade). However, UNIX now incorporates all of the features of a modern GUI and more. UNIX is most popular for companies and large institutions, particularly for multiuser environments. Linux is a UNIX-like operating system for personal computers. Its primary distinguishing feature is that its source code (basically, the text of the program) is freely distributed. A worldwide community of users work to improve Linux. MacOS X is the current operating system for Apple Macintosh computers. Throughout the 1990s the operation systems for the Mac were quite similar to Microsoft Windows. However, in MacOSX Apple has decided to base their operating system on UNIX.
Int 2 Computer Systems - Comp Software
Information Sheet 5.4.1
Produced by P W Shadbolt Queensferry High School 2004
Applications Application programs A Computer Application is a computer program that has been designed to help people with a particular task. Different applications help with different tasks. The one that is used will depend on the type of task that the user wishes to perform. Application packages have been designed to: PROCESS TEXT This type of package can store and process documents that are text based. These packages allow the user to enter, store and retrieve text documents and to perform a wide range of operations on the text. For example, deleting, inserting, spell checking and using search and replace. Text processing packages also allow the user to change the style, font and format of the text. The best example of a text processing package is word processing packages. Text processors would be used to produce letters, reports, PROCESS NUMBERS This type of application is designed to enable the user to enter, store and process numerical data. A spreadsheet package is an example of a number processing package. The working area of a spreadsheet has been divided into rows and columns that form the cells into which the data is entered. Cells can contain text this is generally used for labels and headings, numbers on which the calculations are carried out, and formulae – this defines the calculation to be carried out on the numbers. Number processing applications would be used by accountants, bankers, insurance companies etc. to perform statistical or financial calculations and to process mathematical or scientific data. PROCESS DATA This type of application enables the user to store, manipulate and retrieve collections of data. A database is rather like an electronic filing system/address book that you can question. You can put in as much information as you want and then ask it to sort the information in different ways or search for specific information. In a simple database the data is organised into separate distinct files, each with their own records and fields. In more complex databases the files are linked together to enable the user to perform complicated sorts and searches. Databases are used in a wide range of business, commercial and Government organisations to deal with tasks such as resource management, record keeping and stock control. For example, the Police use databases to keep track of criminals and all the cars in the country. If they wanted to, the Police could give you a list of people who all have the same make, model and colour of car as you in the country. PROCESS GRAPHICS There are 3 main graphics applications - drawing, painting and business graphics packages Drawing Drawing packages store instructions in order to draw shapes. A drawing package is useful for designing; for example; a new kitchen or planning a new house extension as drawing packages can be precise and can scale the drawing up or down, for drawing outlines or for drawing shapes. It is called an object-orientated package, which means that it is made up of a series of objects (lines, boxes, circles etc.), which can be altered and moved around.
Int 2 Computer Systems - Comp Software Produced by P W Shadbolt Queensferry High School 2004
Information Sheet 5.4.2
Applications Painting Painting packages store the drawings as pixels. This is called a bit-mapped package as it draws by filling in the pixels (little dots) on the screen. It is used as though you were painting with pencils and rubber. Painting packages are ideal for producing artistic effects in drawings such as tone and shading. They are good for freehand drawings and are suitable for graphics work where artistic effects are an important element, for example when drawing a poster or a book illustration. It is much more creative than the drawing package. The painting and drawing packages can be easily mixed up. An easy way to remember the difference is that the painting package has a rubber and a spray gun capability. Business Graphics Business graphics applications turn numbers and statistics into graphical form. They are often included in spreadsheet packages and are useful for business reports, presentations, sales figures and exam results. COMMUNICATIONS SOFTWARE Communications software is used to: • regulate the speed of the modem • store and dial phone numbers • establish connections on the phone system • record and carry out logging in procedure. During the transmission, the communications software: • encodes data transmitted • co-ordinates transmissions with other computers • checks for errors in transmission. Communications Software and The Internet Many complex communication tasks must be completed in order to access the Internet. The Internet Service Provider (ISP) supplies the software that provides and carries out these tasks. One of the tasks of the ISP is to manage the user’s connection to the Internet. The World Wide Web (WWW) The WWW is accessed via a browser. A browser is a program that provides the user with the tools to help them navigate through the pages of the WWW. A good browser will provide the following features: • somewhere to enter the address of the page being searched for • a bookmark to allow the user to find useful pages quickly • a home button that takes the user to their own home page • back and forward buttons to take the user through the web pages that they have recently visited • a method of saving useful data to disk. MULTIMEDIA SOFTWARE There are 2 categories of multimedia software. Authoring software and software that provides multimedia-based information systems. Authoring Software Authoring software allows the user to develop projects or presentations, which combine the elements of: • graphics (still and video) • animation • sound • text
Int 2 Computer Systems - Comp Software Produced by P W Shadbolt Queensferry High School 2004
Information Sheet 5.4.2
Applications The user selects what elements they require from a range of files held on backing storage and combines them into a presentation by setting up links between them. Authoring packages are script based whereas the multimedia document is linked together using commands or icons. Multimedia-based Information Systems Multimedia-based Information Systems are commercially based packages that provide information to the user. An example of a multimedia-based system is the encyclopedia Encarta. INTEGRATED PACKAGE Apple Works and Microsoft Works are examples of integrated packages. These consist of a combination of word processing, spreadsheet, database, graphics and communications packages linked together. This makes it easy to combine information from the different packages and it is usually a great deal cheaper than buying the packages individually, although not usually as powerful. Characteristics of an Integrated Package • Integrated packages make it easy to copy data between packages. • Integrated packages reduce the need to enter data as the same data can be used in a whole range of applications. For example, numbers in a spreadsheet file can be transferred to a word processing or database file. • Integrated packages have a common HCI. This means that similar menus, windows, commands and icons are used in each of the applications. This makes it easy to switch between applications and therefore reduces training costs and learning time. • Integrated packages help the user to complete complex tasks as tasks cannot always be solved using the feature in one application package, the user may have to use the facilities of more than one application to complete the task. • Integrated packages help to increase productivity because it is easy to switch between applications and transfer data between them and users do not need to open and close several packages to solve complex problems. Limitations of an Integrated Package • Applications within the package are not as powerful as stand alone or dedicated packages. For example, the word processing package does not offer the same range of functions as a dedicated word processing package.
Int 2 Computer Systems - Comp Software Produced by P W Shadbolt Queensferry High School 2004
Information Sheet 5.4.2
Objects & Operations General purpose packages (GPPs) These are application packages that are in common use and may be supplied with desktop computer systems. GPPs are widespread because the data objects contained in each package fall into the categories of text, number, data and graphics; these are the most commonly used data type in the field of computing. The following table lists some of the objects and operations used in each of the four main GPPs:
Each of the above packages its own native file format; this means the file format in which the package would normally save data. For example:Microsoft Word normally saves data as a Word file although it could be saved as several other data types. In some operating systems (e.g. Windows) the data type can be identified by the file extension; in the case of a Word file this is .doc. If the file is saved as plain text then the extension is .txt, if saved as RFT then it is .rtf. In this way you can tell what type a file is by its name. Standard file formats allow data to be transferred between different computer platforms and also between different applications. A plain text file can be read by a word processor, a spreadsheet package and a database. This makes it possible to export data from any one of these packages and import it into another.
Int 2 Computer Systems - Comp Software
Information Sheet 5.4.3
Produced by P W Shadbolt Queensferry High School 2004
Standard File Formats Application Standards When application packages first became popular one of the main problems was that manufacturers made little effort to ensure that their files could be read by software made by other manufacturers. This was particularly true of word processors, where for example files created in Word could not be used in Wordperfect. Manufacturers made an attempt to address this problem by including the ability to save word-processed files as plain text or ASCII. As all word processors could now read a common file format the situation improved. However, it was soon realised that saving a document as plain text did not include the formatting of the original document (font, bold, italic, etc.). The next aim was to have a common file format that would include the formatting so that documents created in one word processing package could be totally compatible with others. This led to the development of rich text format (RFT), which is still in use today. RTF includes the formatting codes. Many application packages can now save documents in foreign formats to aid the portability of files. Sometimes these problems can cause frustration for users when they want to use another computer to load a file. The problems that can occur are: The backing storage drive is different from the media the file is saved on. For example - the file is saved on a floppy that has been formatted for a Mac and the disc drive will only read PC formatted discs. Differing operating systems and the files won't be recognised. An error message from the operating system will be given to the user. For example - an AppleWorks file was saved on a computer with MacOS 8 and you try to load it on a PC, which has Windows 95 as its operating system. The PC will look for the filename to have a specific suffix e.g. cwk. The computer does not have the appropriate application software. For example, the file was created on Microsoft Word and the other computer only has AppleWorks. Using a different computer or ensuring that your media is formatted for the correct standard or installing different operating system software could resolve the first two problems. The third problem is typical as each application saves files in its own way and other packages find it difficult to read these files. However, standards have been set which allow the user to save data in a format, which can be read by other packages. Standard file formats for text files are: RTF (Rich Text Format), ASCII and text
Int 2 Computer Systems - Comp Software
Information Sheet 5.4.4
Produced by P W Shadbolt Queensferry High School 2004
Standard File Formats RTF Rich Text Format (RTF) is a file format that lets you exchange text files between different word processors in different operating systems.
ASCII ASCII (American Standard Code for Information Interchange) is the most common format for text files in computers and on the Internet.
There are even groups of sad individuals who spend great amounts of time and effort creating complex pictures using ASCII code. A simple search on Google returned more than 7000 sites dedicated to this art form.
Text The term text file is often used as a synonym for ASCII file, a file in which characters are represented by their ASCII codes However, the disadvantage of saving files using these standards is that special formatting created within the original file may be lost e.g. different styles, fonts and sizes. These different formats can usually be chosen in the Save As.... menu using the Format option in each package.
Int 2 Computer Systems - Comp Software
Information Sheet 5.4.4
Produced by P W Shadbolt Queensferry High School 2004
Viruses Viruses Most programs are designed to be useful; some, like viruses, are not! A computer virus is self-replicating piece of computer code that can partially or fully attach itself to files or applications, and can cause your computer to do something you don’t want it to do. Virus behaviour can range from annoying to destructive, but even relatively benign viruses tend to cause harm. Viruses enter your system via e-mail, downloads from the internet, infected floppy disks, homemade CDs and ‘fun’ websites. Currently the primary vehicle for transmission of computer viruses is e-mail. Viruses arrive on a computer as an attachment to an e-mail, which, when opened by the user, sends further copies of itself to everyone in the user’s address book. Clearly such a means of replicating can be highly prolific. In the case of infected floppy disks, the disk acts as a carrier spreading the virus into each machine when it is placed into the drive. Homemade CDs spread viruses in a similar fashion when the original CD has been infected during its compilation. The popular use of programs such as Napster and Kazaa, which allow users anywhere on the internet to share files on each other’s hard drives, has led to concerns about this being used as a means of spreading viruses. According to an article in the UKbased IT site, The Register, 6% of all the music downloaded from KaZaa is virus-laden. When a virus program is executed it tends to perform four actions: 1. replication: copies itself to other files, particularly to .com and .exe files and the boot sector record 2. camouflage: attempts to disguise itself to avoid detection from anti-virus software 3. event watching: whenever the virus runs it checks for certain events, e.g. a specific date, when the virus will activate 4. delivery: this is the purpose of the virus or what it does. This may be a simple jumbling up of letters or wiping an entire hard drive. Signs of a virus There are a number of tell-tale signs that can indicate that your computer has been infected with a virus. They include: • displaying unwanted messages • strange sounds or visual effects • computer keeps rebooting unexpectedly • a flood of unexpected e-mails. A common misconception is that all types of interfering programs are viruses. They aren’t. Worms, Trojan horses and viruses are in a broader category of what analysts call ‘malicious code.’
Int 2 Computer Systems - Comp Software
Information Sheet 5.4.5
Produced by P W Shadbolt Queensferry High School 2004
Anti-Virus Techniques Anti-Virus Software Detection Techniques Anti-virus programs are used to detect and remove viruses. However, detection and removal of viruses are often difficult. Anti-virus software is necessary to help locate viruses and destroy them. Norton AntVirus and Virex are two common anti-virus software. When dealing with these types of viruses as well as using anti-virus software, there are various ways of either preventing viruses or making the virus infection less costly and painful.
Install anti-virus software from a well known, reputable company, Update it regularly, and use it. New viruses come out every single day (see above).
In addition to scanning for viruses on a regular basis, install an 'on access' scanner and configure it to start automatically each time you boot your system. This will protect your system by checking for viruses each time your computer accesses an executable file.
Virus scan any new programs or other files that may contain executable code before you run or open them, no matter where they come from. There have been cases of commercially distributed floppy disks and CD-ROMs spreading virus infections.
Anti-virus programs aren't very good at detecting Trojan horse programs, so be extremely careful about opening binary files and Word/Excel documents from unknown sources. This includes posts in binary newsgroups, downloads from web/ftp sites that aren't well known or don't have a good reputation, and executable files unexpectedly received as attachments to email or during an on-line chat session.
Be extremely careful about accepting programs or other files during on-line chat sessions. This is one of the more common means that users end up with a virus or trojan horse problems.
Do regular backups. Some viruses and trojan horse programs will erase or corrupt files on your hard drive, and a recent backup may be the only way to recover
your data.
Ideally, you should back up your entire system on a regular basis. If this isn't practical, at least backup files that you can't afford to lose or that would be difficult to replace: documents, bookmark files, address books, important email, etc.
INT 2 Computer Systems - Comp Software Produced by S Lambert for Drummond Community High School Computing Department 2004
Infosheet 5.4.6