1.1 System Architecture

Question 1

Basic computer system model

Answer 1

Includes input, processing, output and storage

Question 2

CPU - name and function

Answer 2

Central Processing Unit - Decodes and executes instructions and manages the rest of the hardware.

Question 3

Input device

Answer 3

A device used to input information into the computer

Question 4

Output device

Answer 4

A device that presents data from the computer

Question 5

Storage device

Answer 5

A device on which information can be stored.

Question 6

Von Neumann Architecture

Answer 6

Instructions are fetched, decoded and executed one at a time. Instructions and data are held together in the same memory space.

Question 7

Bus

Answer 7

Paths/lines on the motherboard that data, electrical power and instructions move on.

Question 8

Address Bus

Answer 8

Carries addresses from the processor to memory and input/output devices.

Question 9

Data Bus

Answer 9

Sends data between the processor, memory and input/output devices.

Question 10

Control Bus

Answer 10

Carries signals to co-ordinate computer activities.

Question 11

CU

Answer 11

Control Unit - Co-ordinates activities taking place inside the CPU.

Question 12

Functions of the Control Unit:

Answer 12

1. Controls the execution of instructions in the right order.
2. Decodes the instructions.
3. Regulates and controls processor timing using regular pulses from the system clock.
4. Sends and receives control signals to and from other devices within the computer.

Question 13

ALU

Answer 13

Arithmetic Log Unit. Carries out mathematical and logical operations.

Question 14

ALU functions:

Answer 14

1. Logical Operations: AND, OR, NOT.
2. Shift Operations: The bits in a binary number can be shifted to the left or the right a number of times.
3. Arithmetic Operations: +, -, x, /.

Question 15

What are special Purpose Registers?

Answer 15

Special very fast memory locations within the CPU with specific purposes in the process of executing instructions.

Question 16

MAR

Answer 16

Memory Address Register - Holds the address of data ready for use by the MDR, or the address of an instruction passed from the PC.

Question 17

MDR

Answer 17

Memory Data Register - Holds data fetched from or to be written to memory.

Question 18

PC

Answer 18

Program Counter - The register that contains the address of the next instruction to be executed. It is incremented for each
instruction of the program being executed.

Question 19

ACC

Answer 19

Accumulator - Holds the result of calculations.

Question 20

FDE Cycle

Answer 20

Fetch-Decode-Execute. The CPU uses this cycle to carry out program instructions.

Question 21

Fetch

Answer 21

1. The contents of the Program Counter are put into the MAR.
2. The address is transferred along the address bus to main memory.

Question 22

Decode

Answer 22

The CU decodes the instruction in the CIR to see what is to be done next.

Question 23

Execute

Answer 23

The instruction is then executed.

Question 24

Factors affecting the speed of the CPU.

Answer 24

1. Clock Speed
2. Cache size
3. Number of cores

Question 25

Embedded system + example

Answer 25

A computer system within a larger mechanical or electrical system designed for a specialist purpose. Example - coffee machine

Question 26

Multi-tasking

Answer 26

Creating the illusion that many programs are running at the same time (rapidly switches between programs)

Question 27

Primary storage -

Answer 27

Volatile, short-term, fast memory. Includes registers, cache and RAM.

Question 28

Random Access Memory (RAM)

Answer 28

a type of volatile primary storage that stores programs and files that are currently in use.

Question 29

Volatile

Answer 29

when the power is turned off, the contents are lost.

Question 30

Virtual Memory

Answer 30

when a portion of the Hard Disk Drive (HDD) is used as though it is RAM (hence “virtual”). When RAM fills up, it can use this to keep the programs running without having to close them.

Question 31

Cache

Answer 31

very high speed memory next to the CPU that stores frequently used instructions + data

Question 32

Secondary storage

Answer 32

non-volatile, long term storage for programs, files and other data. E.g. HDD/SSD, CDs/DVDs.

Question 33

Optical storage

Answer 33

CDs and DVDs.

Question 34

Magnetic storage

Answer 34

Hard Disk Drives. It uses a moving read-write head that passes over magnetised platters. HDDs can be a bit unreliable due to moving parts than can wear out and break

Question 35

Solid state drives…

Answer 35

uses Flash chips which has no moving parts and is much faster and more durable than a Hard Disk Drive.

Question 36

Read-Only Memory (ROM)

Answer 36

a type of storage that can only be read from and not written to. The most common use of ROM is to store the basic BIOS settings that boot up the computer.

Question 37

Units of storage:

Answer 37

• Bit = 1 or 0 (smallest unit of data).
• Nibble = 4 bits
• Byte = 8 bits
• KiloByte = 1024 Bytes
• MegaByte = 1024 x 1024 (roughly 1 million) Bytes
• GigaByte = 1024 x 1024 x 1024 (roughly 1 billion) Bytes
• TeraByte = 1024 x 1024 x 1024 x 1024 (roughly 1 trillion) Bytes

Question 38

Characteristics of secondary storage that need to be considered when buying devices for certain scenarios:

Answer 38

• capacity (amount of data it can store)
• speed (how fast data can be read and written to it)
• portability (how easy it is to carry about)
• durability (how difficult it is to break)
• reliability (how long it tends to last without going faulty)
• cost (per byte or Gigabyte)