Computers

Question 1

What is the stored program concept?

Answer 1

Where there is main memory and a CPU interconnected by buses with there being some form of secondary storage to provide long term storage

Question 2

What is the purpose of the control unit?

Answer 2

Decodes instructions received from main memory and coordinates the actions of the other parts of the CPU in order to execute them

Question 3

What is the purpose of the arithmetic logic unit?

Answer 3

Performs arithmetic and logical operations on data

Question 4

What is the purpose of registers?

Answer 4

Fast temporary storage for instructions, intermediate results and data

Question 5

What is the purpose of the clock?

Answer 5

Synchronises other hardware components. the faster the clock, the more instructions can be executed per second

Question 6

What are the purposes of the buses?

Answer 6

Control bus (bidirectional): Carries signals between the control unit and other components
Address bus (unidirectional): Carries the address of the memory location that the CPU will read from or write to
Data bus (bidirectional): Transfers program instructions and data between memory and the CPU

Question 7

How does the fetch-decode-execute cycle work?

Answer 7

Fetch: The CPU places the memory address of the next instruction on the address bus. The CU sends a read signal along the control bus to memory. The content of the specified memory location is transferred along the data bus to the CPU. It’s stored in registers on arrival
Decode: The CU looks up the instruction in the CPU’s instruction set
Execute: The CU coordinate the actions of other components of the CPU to carry out the operation

Question 8

Why is secondary storage needed?

Answer 8

Secondary storage is non-volatile so when turned on, it keeps its memory

Question 9

What is an example of magnetic storage?

Answer 9

Hard disk drive (HDD)

Question 10

How do you write on a HDD?

Answer 10

The read-write head magnetises the surface of the platter to a 1 or a 0. Data is stored on concentric tracks subdivided into sectors

Question 11

How do you read on a HDD?

Answer 11

The read-write head detects the magnetic state of the platter

Question 12

What is an example of optical storage?

Answer 12

CDs or DVDs

Question 13

How do you write optical storage?

Answer 13

A laser burns the surface of the disk, making it more or less reflective. More reflective surfaces are called lands and represent 1. Less reflective surfaces are called pits and represent 0

Question 14

How do you read optical storage?

Answer 14

A laser beam is shone onto the surface of the disk. A land which reflects more light than a pit represents 1 which is detected by a light sensor

Question 15

What is an example of solid-state storage?

Answer 15

Solid state drive (SSD)

Question 16

How do you write an SSD?

Answer 16

A current is applied to the transistor, forcing electrons into pools. A full pool represents 0 and an empty pool is 1

Question 17

How do you read an SSD?

Answer 17

A small voltage is applied. If the pool is empty, the transistor turns on and a 1 is read. If the pool is full, the transistor doesn’t turn on and a 0 is read

Question 18

What are the features of an embedded system?

Answer 18

1. Single purpose
2. Customised hardware and software
3. Low power consumption
4. Minimal or no UI

Question 19

What are the main tasks performed by an operating system?

Answer 19

1. Process management
2. File management
3. User management
4. Peripheral management

Question 20

How does an OS manage processes?

Answer 20

It uses a scheduling algorithm to ensure that every process gets a share of CPU time

Question 21

How does an OS manage files?

Answer 21

It has a root directory branching off into different nodes which are either sub-directories or files

Question 22

How does an OS manage users?

Answer 22

Access control: Uses login names and passwords to authenticate users
User interface: OS provides a user interface to interact with the computer
File permissions: OS grants user permissions to either read, write, execute or delete files

Question 23

How does an OS manage peripherals?

Answer 23

The OS uses device drivers to communicate with peripheral devices

Question 24

What does data compression software do?

Answer 24

Reduces the file size by repackaging it or removing some data so that it takes up less space in secondary storage

Question 25

What does file repair software do?

Answer 25

Recovers data from repair files that have been corrupted. It scans the damaged file and extracts as much data as possible in a new file

Question 26

What does disk defragmentation software do?

Answer 26

Rearranges individual file blocks for each file so that they are stored in contiguous blocks on the disk to speed up access to files stored on a magnetic hard drive

Question 27

What does backup software do?

Answer 27

Keeps a copy of files so that, should a file get lost or damaged, the most recent backup can be recovered. It keeps backups of files made at regular intervals and stored on a separate device in a different location to the live working environment

Question 28

What does anti-malware software do?

Answer 28

Protects computer systems and data from damage caused by malware. It has a database of malware signatures and detects if a file has a pattern that matches a known signature. It then deletes it

Question 29

How can code reviews make robust sofware?

Answer 29

It can be carried out by other programmers or by specialised software that checks the code to make sure it meets a pre-defined set of rules and may suggest ways to fix bugs and security issues

Question 30

How can audit trails make robust software?

Answer 30

The audit trail keeps track of who made what changes and when during the development process. If a problem arises, it can be tracked back to its source and rolled back to a version before the flaw was introduced

Question 31

What are properties of low-level languages?

Answer 31

1. Difficult and time consuming to use 2. Few tools to help with maintenance and debugging 3. Machine-specific programs 4. Interact directly with hardware enabling memory to be used more efficiently

Question 32

What are the properties of high-level languages?

Answer 32

1. Are programmer-friendly 2. Have tools that make maintenance and debugging easier 3. Are machine-independent 4. Generally, less memory efficient

Question 33

How do compilers work?

Answer 33

It translates the source code into machine code which can then be executed

Question 34

What are the advantages of compilers?

Answer 34

1. The translation is only done once as a separate process 2. The program that is run is already translated into machine code so it can be executed more rapidly 3. The code is protected from competitors as they cannot see the source code

Question 35

What are the disadvantages of compilers?

Answer 35

1. if it encounters any errors, it carries on trying to compile the program and reports the errors at the end 2. You cannot change the program without going back to the original source code, editing that and recompiling

Question 36

How do interpreters work?

Answer 36

It translates the high-level code line by line into machine code

Question 37

What are the advantages of interpreters?

Answer 37

1. When an error is found, it stops and pinpoints the error so that the programmer knows where it has occurred 2. The code is not platform-specific and can be run on different operating systems and platforms as long as there is an interpreter 3. The program can be easily edited as it always exists as source code

Question 38

What are the disadvantages of interpreters?

Answer 38

1. Every line has to be translated each time it is executed so it's slower to run