Components of a Computer- S1

Question 1

The Central Processing Unit

Answer 1

the CPU or the processor, has a number of different components which enables the it to carry out its task of execution instructions.

Question 2

Control unit

Answer 2

controls and coordinates the activities of the CPU It accepts next instructions and decodes it

Question 3

Bus

Answer 3

a set of parallel wires connecting two or more components of a computer
The processor is connected to the main memory by three busses known as the system bus. Only one signal can be transmitted along a bus at a time.

Question 4

Address Bus

Answer 4

The address bus transmits the memory addresses so that data can be retrieved and sent back to the processor. Data can only be sent one way (CPU to memory)

Question 5

Data bus

Answer 5

The data bus, provides a bidirectional path for moving data and instructions from memory to location. (carries data between register components)

Question 6

Control Bus

Answer 6

transmits control signals (from the control unit) to the rest of the processor (commands, timing) Data is a bi-directional bus between, CPU to memory or I/O devices.

Question 7

Arithmetic-Logic Unit (ALU)

Answer 7

performs arithmetic and logical operations on the data. E.g subtract, shift operations within a register, Boolean logic operations.
Acts as a conduit through which all I/O to computer is done/gateway to the processor.

Question 8

Fetch phase

Answer 8

1) The address of the next instruction is copied from the PC to the MAR
2) The instruction held at that address is copied to the MDR, and 1+ is added to the PC so it holds the address of next instruction.
3) The contents of the MDR are copied to the CIR.

Question 9

Decode phase

Answer 9

The instruction in the CIR is decoded. The instruction is split into the opcode and the operand (the data that will be operated on).

Question 10

Opcode

Answer 10

the instruction

Question 11

Operand

Answer 11

the data that will be operated on

Question 12

Registers

Answer 12

Provide fast access to data for when frequent access is needed like in the fetch execute cycle. It is used for temporary storage.

Question 13

Memory Unit

Answer 13

Stores OS
 Stores data (currently in use)
 Stores software(currently in use)/boot
program/operations/instructions.

Question 14

Difference between RAM and ROM

Answer 14

• RAM is volatile/ROM is not volatile
• RAM is editable/ROM cannot be altered
• RAM is larger/ROM is smaller

Question 15

Whats stored in RAM

Answer 15

Programs, software and data in use so that it can be accessed faster than the hardrive

Question 16

What software is stored in RAM

Answer 16

Bootstrap, must be available when computer switched off in order to start the computer

Question 17

Program Counter

Answer 17

-Is needed to store the address of the next instruction
-Value is then sent to the MAR
-After sending the value the PC is incremented
-OR the PC changes to address
held in CIR if the operation is a Jump

Question 18

Memory Address Register

Answer 18

Contains the address of the instruction sent from PC

or sent from CIR

Question 19

Memory data register(MDR)

Answer 19

• Contains the instruction which has been accessed from memory
• That is referenced by the MAR
• Instruction sent to CIR
• MDR acts as a buffer

Question 20

Accumulator(ACC)

Answer 20

Temporary storage that holds data being used during

calculations. It deals with input & output in the processor.

Question 21

Current instruction Register(CIR)

Answer 21

holds the current instruction being executed. Which is divided into operand and opcode.

Question 22

Name two architecture you can get for processors

Answer 22

The von Neumann and Harvard architecture

Question 23

What is the architecture of the Von Neumann

Answer 23

A program must be resident in main memory to be executed
Instructions are fetched from memory one at a time, decoded and executed in the processor.
There will be a CPU, Arithmetic Logic Unit and main memory (RAM).
Data bus transfers data and instructions, so instruction fetch and a data operation cannot occur at the same time
An address bus transfers addresses and instructions.

Question 24

Problems with the Von Neumann architecture

Answer 24

The data bus is slower than the rate at which the CPU can perform instructions and the speed of the processor is limited by the data transfer (bottleneck).

Question 25

Harvard Architecture

Answer 25

• Instructions and data are held in separate memories
• Parallel data and instruction buses may be used
• Programs tend to be large
• The CPU can be fetching both instructions and data at the same time.
• Harvard can be faster the von Neumann

Question 26

What two types of Instruction Sets can you get?

Answer 26

CISC (Complex Instruction Set Computers)

RISC (Reduced Instruction Set Computers)

Question 27

CISC

Answer 27

Has a large instruction set to to accomplish tasks in as few lines of assembly language as possible. Complex instructions are built into the machine’s hardware.

Question 28

RISC

Answer 28

One instruction performs a simple task and there is only a limited number of instructions available. Therefore complex tasks can only be performed by combining multiple instructions.

Question 29

Difference between CISC and RISC

Answer 29

RISC has…
Has simpler hardware
More complicated software code
Takes one cycle per instruction (pipelining is possible)
Uses more RAM to handle intermediate results
More to compile
Used in smartphones and tablets, as they need less power and less energy. whereas CISC used in PCs

Question 30

Whats an instruction set

Answer 30

all the instruction in machine code that are recognised and executed by the CPU

Question 31

What two types of systems can be used for a processor

Answer 31

Co-processor and multi-core

Question 32

Co-processor

Answer 32

Designed to carry out specific task, usually floating point calculation,graphics and digital signalling processing, which would take up a lot of processor time.

Question 33

Multi-core`

Answer 33

Multi-core CPUs can distribute workload across multiple CPU cores, achieving higher performance. This is used in supercomputers when there is a lot of processing needed

Question 34

When will multi-core not work?

Answer 34

When a problem/operation can not be broken down and distributed

Question 35

Input

Answer 35

Inputs consist of data or commands that enter the computer system.

Question 36

Output

Answer 36

Where the information obtained after processing is presented to the user. It might be something you see, hear, smell, read.

Question 37

What is an Actuators

Answer 37

motors in conjunction with sensors to control a mechanism like opening windows, starting pump, turning a wheel

Question 38

Storage Device

Answer 38

Storage devices are secondary storage and are used to store data and software for later. It is not directly accessible to the processor like RAM and has a slower access speed, but it retains its contents when the computer it turned off.

Question 39

Give examples of Storage Devices

Answer 39

Hard Drive, Magnetic Tape, CD/DVD, USB/Flash memory,

Question 40

Out of CIR, MDR and PC which hold binary numbers?

Answer 40

All of them

Question 41

Out of CIR, MDR and PC which always hold only an address

Answer 41

PC

Question 42

Out of CIR, MDR and PC which can change more than once during a cycle

Answer 42

PC and MDR

Question 43

Out of CIR, MDR and PC which may pass a value to the MAR

Answer 43

PC and CIR

Question 44

Give the name of the computer architecture that uses fetch-execute cycle with a single control unit

Answer 44

Von Nueman architecture

Question 45

Explain once other advantage excluding cost of RISC compared with CISC

Answer 45

RISC runs faster due to simpler instructions

Question 46

Describe three different input devices used by police

Answer 46

Fingerprint scanning- digitises image and compares with those held in database.
DNA analysis looks for similarities in DNA in two samples.
Cameras (security in shops) which record.