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Form 4 JL

1. Complete the following statements by filling the blanks. All data flows inside the computer has to go through different channels called the ________bus. The _______ bus is used by the processor to choose a specific memory location in the RAM, ROM or in specific I/O chips. The address bus works in _______way (unidirectional). The larger the address bus, the larger the _______ space. The _______ bus is used to transfer data between the processor, the RAM, the ROM or other peripheral devices. The data bus is a _______-way carrier. The _______ bus is like a traffic light, it provides the timing signals used to synchronize when the data is to be sent in order to avoid conflict in data transfers. 2. Indicate in which CPU Unit are these registers found: Accumulator

_____________________________

Memory Address Register

_____________________________

Program Counter

_____________________________

Memory Data Register

_____________________________

Instruction Register

_____________________________

3. Explain the function of each of the following. Arithmetic Logic Unit ____________________________________________________________________________ ______________________________________________________________________________________________ Control Unit ___________________________________________________________________________________ ______________________________________________________________________________________________ Memory Unit __________________________________________________________________________________ ______________________________________________________________________________________________ 4. The 3 main units of the CPU are linked together by what is known as the system bus. A. What is meant by system bus? ______________________________________________________________________________________________ ______________________________________________________________________________________________ B. How does the number of lines in the data bus affect the performance of a computer? ______________________________________________________________________________________________ ______________________________________________________________________________________________ C. How does the number of lines in the address bus determine the address space? ______________________________________________________________________________________________ _____________________________________________________________________________________________ Daniela Attard

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5. Complete the following statements about the CPU by filling the blanks. The ______________ is the master or controlling unit which co-ordinates the activities of the other two units being the ______________ and the ______________ Arithmetic Logic Unit. The CU is subdivided in two registers being the ______________ which stores each instruction read by the CU from the main memory and the ______________ which is the register that contains the address of the next machine-code instruction in the program to be fetched from memory. The register is automatically incemented by 1 as soon as each instruction is read. The ______________ is also part o the CPU. It performs the four basic arithmetic operations (+, -, /, *). It is lso capable of carrying out comparisons such as (=,<,>,<=,>= and <>) and also performs the logic functions (AND, OR, NOT). This unit is made up of the ______________ which is used for receiving and holding the results of a computation or of data transfer and the ______________ which is capable of shifting its binary digits. 6. If the main memory of a byte computer contains a 10-line address bus and an 8-line data bus. What is the storage capacity of that memory? _______________________________________________________________________________________________ 7. Find the maximum address that can be held in 16 bits in binary. (Remember that address locations start from 0) _______________________________________________________________________________________________ 8. Describe the purpose of the following registers: A. What does the program counter store? _______________________________________________________________________________________________ _______________________________________________________________________________________________ B. What is the instruction register used for? _______________________________________________________________________________________________ _______________________________________________________________________________________________ C. What is the purpose of the accumulator _______________________________________________________________________________________________ _______________________________________________________________________________________________

9. Describe how the CPU can read from and write to main memory using the address bus and the data bus. Where does the control bus come in? _______________________________________________________________________________________________ _______________________________________________________________________________________________ _______________________________________________________________________________________________ _______________________________________________________________________________________________ _______________________________________________________________________________________________ _______________________________________________________________________________________________ Daniela Attard

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10. Complete the following statements by filling the blanks using the words below. CPU

BASIC

Fetch-execute

Opcode

Registers

Address

Machine-Code

Program-counter

Disk

Operands

ALU

Instruction

Keyboard

Executed

Data

A ______________ instruction is made up of an ______________ specifying the operation to be performed by the ______________ , followed by zero or more ______________ , specifying the data on which the operation is to be performed. At the beginning of a ______________ cycle, the CPU places the contents of the ______________ on the ______________ bus and receives the net instruction over the ______________ bus. The instruction is stored in the ______________ register while it is being decoded and ______________ . 11. What is meant by a CPUâ&#x20AC;&#x2122;s instruction set? _______________________________________________________________________________________________ _______________________________________________________________________________________________ 12. A particular opcode is made up of 6 bits. How many unique instructions can this opcode represent? _______________________________________________________________________________________________ _______________________________________________________________________________________________ 13. Why does each instruction has to be translated to machine code in order to be executed by the CPU? _______________________________________________________________________________________________ _______________________________________________________________________________________________ 14.(a) Shift these binary numbers by one to the right: Binary Number

Decimal Equivalent

Result of shift (binary)

Decimal Equivalent

Result of shift (binary)

Decimal Equivalent

01001110 10001010 00000010

(b) Shift the same numbers by two to the right: Binary Number

Decimal Equivalent

01001110 10001010 00000010

(c) What is the difference between shifting the number by one and shifting the number by two to the right? What happens when the above numbers are shifted to the left? _______________________________________________________________________________________________ _______________________________________________________________________________________________ Daniela Attard

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15. What do the terms Fetch and Execute mean? _______________________________________________________________________________________________ _______________________________________________________________________________________________ _______________________________________________________________________________________________ _______________________________________________________________________________________________ 16. Fill in the steps of the Fetch-and-Execute cycle

17. For the following questions, choose the correct answer A. What is the correct definition of the term 'instruction set'? a) The range of opcodes which a CPU is programmed to recognise b) The list of instructions in memory which forms the program being executed c) A specific subroutine of a program, run if conditions relating to the flag register are satisfied d) The process by which a single instruction of a program is executed

B. Which of the following is NOT one of the three stages of the instruction execution cycle? a) Decode b) Fetch c) Flag d) Execute

C. Which of the following registers set the value to the address of the first instruction a) Instruction Register b) Program Counter c) Shift Register d) Accumulator

D. The OPERAND indicates: a) b) c) d)

Where the data required for the operation can be found What operation is expected to be performed The address of the next instruction to be executed The value of the accumulator

D. The OPCODE indicates: a) b) c) d)

Where the data required for the operation can be found What operation is expected to be performed The address of the next instruction to be executed The value of the accumulator

Daniela Attard

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CPU Worksheet Junior Lyceum