Terms

Question 1

ALU

Answer 1

Arithmetic Logic Unit: “The part of the CPU where data is processed and manipulated. This processing and manipulation normally consists of arithmetic operations or logical comparisons allowing a program to make decisions.”

Example sentence: The ALU performs calculations such as addition and subtraction.

Question 2

Control Unit

Answer 2

The part of the CPU that manages the execution of instructions. The control unit fetches each instruction in sequence, and decodes and synchronises it before executing it by sending control signals to other parts of the computer.

Example sentence: The control unit coordinates the flow of data within the CPU.

Question 3

Register

Answer 3

Tiny areas of extremely fast memory located in the CPU normally designed for a specific purpose, where data or control information is stored temporarily.

Example sentence: Registers are used to store intermediate data during calculations.

Question 4

Program Counter

Answer 4

A register in the control unit which holds the address of the next instruction to be executed.

Example sentence: The program counter keeps track of the current instruction being executed.

Question 5

Accumulator

Answer 5

A special register within the ALU. It is used to hold the data currently being processed by the central processor. Any data to be processed is stored temporarily in the accumulator, the results ending up back in the accumulator being stored in the memory unit.

Example sentence: The accumulator stores the result of arithmetic operations.

Question 6

Memory Address Register

Answer 6

A register in the CPU that stores the address of the memory location currently in use. In the fetch phase, this would be the address of the instruction being loaded; in the execute phase, it would be the address of the data being used.

Example sentence: The memory address register holds the location of data in memory.

Question 7

Memory Data Register

Answer 7

A register in the CPU that stores data being transferred to and from the immediate-access store. It acts as a buffer, allowing the central processor and memory unit to act independently without being affected by minor differences in operation. A data item will be copied to the MDR ready for use at the next clock pulse, when it can either be used by the central processor or be stored in main memory.

Example sentence: The memory data register holds data temporarily during processing.

Question 8

Current Instruction Register

Answer 8

A register in the control unit that stores the address of the next instruction currently being executed and decoded.

Example sentence: The current instruction register keeps track of the instruction being executed.

Question 9

Busses

Answer 9

A common physical pathway shared by signals to and from several components of a computer.

Example sentence: Busses allow communication between different parts of the computer.

Question 10

Data Bus

Answer 10

The part of the bus which carries the actual information.

Example sentence: The data bus transfers data between the CPU and memory.

Question 11

Address Bus

Answer 11

The part of the bus which carries identification about where the data is being sent.

Example sentence: The address bus specifies the memory location for data transfer.

Question 12

Control Bus

Answer 12

This bus carries command and control signals to and from every other component of a computer.

Example sentence: The control bus coordinates communication between different parts of the computer.

Question 13

Fetch-Decode-Execute

Answer 13

The complete process of retrieving an instruction from store, decoding it and carrying it out. Also known as the instruction cycle.

Example sentence: The fetch-decode-execute cycle is essential for executing instructions.

Question 14

CPU

Answer 14

Central Processing Unit: “The main part of the computer, consisting of the registers, ALU and control unit.”

Example sentence: The CPU is responsible for executing instructions.

Question 15

Clock Speed

Answer 15

Measured in Hertz, the clock speed is the frequency at which the internal clock generates pulses. The higher the clock rate, the faster the computer may work. The “clock” is the electronic unit that synchronises related components by generating pulses at a constant rate.

Example sentence: A higher clock speed allows for quicker processing of tasks.

Question 16

Control unit

Answer 16

The part of the processor that coordinates the activity of all the other components

Question 17

Control signals

Answer 17

Sent along the control bus between the control unit and other components if the computer

Question 18

What is a bus

Answer 18

Buses in a computer consist of a series of connectors that transfer signals between the internal components

Typically consisting of 8, 16, 32 or 64 lines

Question 19

The system bus consists of three separate buses carrying…

Answer 19

Control signals
Addresses
Data

Question 20

Memory read

Answer 20

Causes data from the addressed location in RAM to be placed on the data bus

Question 21

Memory write

Answer 21

Causes data on the data bus to be written to the addressed location in RAM

Question 22

Bus request

Answer 22

Indicates a device is requesting use of the data bus

Question 23

Bus grant

Answer 23

Indicated the cpu has granted access to the data bus

Question 24

Clock

Answer 24

Used to synchronise operations

Question 25

ALU

Answer 25

The problem solving part of the processor:
. Component performs arithmetic, logical and shift operations on data
. Arithmetic operations: Add, Subtract, Multiply and Divide
.Logical operations include: AND ,OR , NOT, XOR
.shift operations: move bits to the left or right within a register

Question 26

Why use registers

Answer 26

Rather than writing working data back to ‘slow’ memory processors have several locations of super-fast memory called registers that are used to temporarily store results

The processor is then immediately able to access and re-use these resukts in subsequent calculations

Question 27

Carrying out a sequence of programming instructions requires many different leices of info to be held

Answer 27

.the processor has to temporarily hold the current instruction being executed
.it has to hold the address of the data that it needs, and also the data itself
.it has to keep track of the address of the next instruction

Question 28

Program counter

Answer 28

Holds the memory address of the next instruction to be executed

Question 29

Currebt instruction register

Answer 29

Holds the current instruction, which is split into opcode and operand

Question 30

Memory address register

Answer 30

Holds the address in memory where the processor is required to fetch or store from or to

Question 31

Memory data register

Answer 31

Temporarily holds data moving between the processor and main memory

Question 32

Accumulator

Answer 32

To hold intermediate results of an instruction

Question 33

What is the role of the processor

Answer 33

To carry out instructions from programs stores in memory

Question 34

Fetch (steps 1-4)

Answer 34

1. The address of the next instruction is copied from the PC to the Memory Address Register (MAR)
2. The instruction held at the address is copied to the Memory Data Register (MDR)
3. Simultaneously, the contents of the Program Counter(PC) are incremented
4. The contents of the MDR are copied to the Current Instruction Register (CIR)

Question 35

Decode (steps 5 - 7)

Answer 35

5. Instruction held in the CIR is decoded
6. It is split into operand and opcode to determine the type of instruction it is. Additional data, if required, is fetched from memory
7. And passed to the accumulator
   -the opcode specifies the operation that is to be carried out
   -the operandi holds either:
   The address of the data to be used, which is then copied to the MAR or

The actual data to be operated on, which is passed to the MDR

Question 36

Execute (step 8)

Answer 36

The instruction is executed and the result held in the accumulator or stored in memory