Computers

Question 1

Von Neumann architecture

Answer 1

A structure in which the hardware is connected and organised.
It consists of Main Memory and a Central Processing Unit interconnected by buses.

__________Main Memory
________ (Read)!_____¡(Write)
Input –> Central Processing Unit –> Output

The CPU reads and writes data & program instructions to and from main memory.

Question 2

Main memory

Answer 2

Known as Random Access Memory(RAM)
It stores the data & programs the CPU can access.
Volatile - Loses content when power is lost.

Faster and more expensive than secondary storage

Question 3

Programmable computer

Answer 3

A computer that is multi-purpose, can be programmed to carry out different tasks. They are able to store program instructions and data in main memory.

Question 4

CPU parts

Answer 4

Consists of:
- Control Unit (CU)
- Arithmetic Logic Unit (ALU)
- Registers

Question 5

Control unit (CU)

Answer 5

• Decodes instructions received from main memory
• Coordinates the actions of other components

Question 6

Arithmetic Logic Unit(ALU)

Answer 6

Performs arithmetic and logic operations on data.

Question 7

Registers

Answer 7

Provides fast, temporary storage for instructions.

Question 8

Buses

Answer 8

Buses connect the components inside a computer.
Types:
- Address bus
- Data bus
- Control bus

Question 9

Address bus

Answer 9

Carries the address of the memory location. Unidirectional, only the CPU can put an address on this bus.

Question 9

Data bus

Answer 9

Holds the value being read from or written to memory. Bidirectional.

Question 10

Control bus

Answer 10

• Carries command signal from the control unit to other components. The status signal is sent back to the CPU.
• Bidirectional.

Question 11

Clock

Answer 11

A tiny quarts crystal that vibrates and sends out electronic signals to synchronise the actions of the hardware components.
Measured in hertz, 1 hertz = 1 “tick” per second.

Question 12

Fetch/Decode/Execute cycle

Answer 12

Program instructions and data are stored in main memory and transferred/fetched one data at a time to the CPU, where they are decoded and executed.

Fetch: The control unit sends a read signal to main memory along the control bus. It also places the memroy address of the next instruction on the address bus. The RAM copies the content of the memory location indicated by the address bus on the the data bus.

Decode: The control unit decodes the instructions.

Execute: The control unit sends signal to the other components of the CPU instructing them what to do.

Question 13

Secondary Storage

Answer 13

• Non-volatile
• Allows the system to store data and programs permanently.
• Cheaper and slower than main memory.

Types:
- SSD(Solid State Drives): USB drive
- Magnetic storage: HDD(Hard Disc Drive)
- Optical Storage: DVD/CD

Question 14

Magnetic Storage

Answer 14

• A head reads & writes to spinning discs.
• An area that is magnetised represents a 1.
• An area that is not magnetised represents a 0.

Question 15

Solid State Drive

Answer 15

• Represents bits by little pools of trapped electrons on a microchip.
• No flow(trapped) represents a 0.
• Electron flow represents a 1.

Question 16

Optical storage

Answer 16

• Laser beam reads and writes data(Pits and land)
• Pit represents a 0
• Land represents a 1

Question 17

Operating system (OS)

Answer 17

A program that controls and manages the hardware and all other software on a computer and provides an interface for users

Question 18

Application software

Answer 18

Programs or apps deigned for end users.
Such as:
- Web browser
- Spreadsheet
- Game

Question 19

Utility software

Answer 19

Programs that functionality to a computer system or improve its performance in some way.
Such as:
- Disk repair
- Compression
- Anti-malware

Question 20

Why is robust software made

Answer 20

To produce software that is capable of handling the unexpected without crashing, not generating incorrect output, or not revealing sensitive data

Question 21

Bad programming practices

Answer 21

• Not having a well-thought design
• Not following coding standards
• Using a temporary fix
• Writing unstructured code
• Not testing

Question 22

Scheduling

Answer 22

• All processes are held in a queue
• Some processes are prioritised
• Processes are allocated time slides, length of time slices depends on priority. Processes are switched at the end of their time slice
• Unfinished processes are put to the back of the queue
• During the time slice, the process has exclusive use of the processor

Question 23

Types of operators

Answer 23

• Relational
• Arithmetic
• Logical

Question 24

Relational

Answer 24

<, >, !=, ==

Question 25

Arithmetic

Answer 25

+, -, *, /

Question 26

Logical

Answer 26

AND, OR, NOT

Question 27

Write data in SSD

Answer 27

• Current applied to a transistor
• Forces electrons through a barrier, trapping them in pools
• Full pool (0), Empty pool (1)

Question 28

Disk fragmentation

Answer 28

• Files are written to a disk in blocks
• Blocks can be dispersed through the disk

Question 29

Disk defragmentation

Answer 29

• When file blocks are rearranged in the disk
• To place free space together / file blocks together

Question 30

Audit trails

Answer 30

• Keeps track of who made what changes
• Allows to track back problems
• Enables program to be rolled back
• Help produce robust software

Question 31

Code reviews

Answer 31

• Check that software adheres to agreed standards
• Find instances of inefficient code
• Identify potential vulnerabilities
• Done by programmer

Question 32

Compiler

Answer 32

Translates the source code into a stand-alone machine code program that can be executed by the processor

Question 33

Interpreter

Answer 33

Translates a high-level code line by line into machine code. It is needed each time the program is run

Question 34

Cache

Answer 34

• Store frequently used instructions (act as a buffer)