Computer Science ( Computer Systems )

Question 1

Explain the Fetch-Decode-Execute

Answer 1

1. Fetch - The memory address is copied from the program counter to the MAR.
2. Fetch - the instruction stored in the MAR is copied to the MDR.
3. Decode - The instruction the MDR is then decoded by the CU
4. Execute - The instruction is then performed

Question 2

Memory

Describe what Virtual Memory is & how it functions.

Answer 2

1. When the RAM is full, Computers move data that hasn’t been used recently to a location on secondary storage, virtual memory.
- VM may be needed if; too many applications open, or a particularly memory-instensive application is open.

2. If the CPU has to read data from VM, it must move the data back to RAM, This is slow as data transfer rates are much slower on Secondary Storage than RAM.

3. VM can make a computer slow to respond when switching between applications.

Question 3

CPU and System Performance

Describe the different factors that can affect CPU performance.

Answer 3

1. Clock Speed
   - This the number of instructions a single processor core can carry out per econd.
   - The higher the clock speed, the greate number of instruction that can be carried out per second.
   - Some CPUs can be overclocked to make them run a

Question 4

What are some Pro’s & Con’s of;
A) Lossy Compression
B) Lossless Compression

Answer 4

A) Lossy ( MP3 { Audio }, AAC { Audio }, JPEG { Image } )

1. Advantages Include;
- Greatly reduced file size, meaning more files can be stored.
- Lossy files take up less bandwidth so can be download & streamed more quickly
- Commonly used, lots of softare can read lossy files

2. Disadvantages Include;
- Lossy compression loses data.
- Lossy compression cannot be used on text files.
- While the quality will be worse, its usally unnoticable

B) Lossesless ( FLAC { Audio }, TIFF { Image }, PNG { Image } )

1. Advantages Include;
- Data is only removed temporarily so there is no reduction in quality.
- Lossess files can be decompressed.
- Lossless compression can be used on text & software files.

2. Disadvantages Include;
- Only a slight reduction in file sizes

Question 5

What are some Advantages;
A) Wired Networks
B) Wireless Networks

Answer 5

A) Wired Networks

1. Advantages Include;
- Generally faster, offering higher data transfer speeds.
- Lower latency, ( Important for airports that are always updating flight times )
- More reliable, less prone to interference. ( Important for airports due to the amount of people ).

B) Wireless Networks

1. Advantages Include;
- No need for physical cables. ( Good for public due to increased flexibility )
- Prevents hazards in congested areas ( Good for public due to airports being busy )

Question 6

,

What is an Embedded System?

Answer 6

1. Embedded systems are computers built into other devices.

2. As they’re dedicated to a single task, embedded systems are usually easier to design.

Question 7

What are some things stored in the;
A) RAM
B) ROM

Answer 7

A) RAM Include;

• All the data, files and programs are stored while they’re being used.
• The Operating Systems ( User Interface, Graphical User Interfaces )

B) ROM Include

• The BIOS - All the instructions need to properly boot up
• The Bootstrap ~ Process of locating the operating system.

Question 8

List & Explain Some Different Utility Softwares

Answer 8

A) Disk Defragmentation
Reason Needed: Files are stored on hard disk, When files are moved, deleted or change size, lots of small gaps appear in the disk.
- Reason Needed: Over time the disk becomes more and more fragmented. This makes the reading & writing speeds much slower.
- Why It’s Needed: Defragmentation re-organises data on the hardrive to put the fragmented files back together.

B) Compression Software

1. Compression software reduces the size of files by permanetly or temporarily removing data from them.

C) Encryption Software

1. Encryption software scrambles data to prevent 3rd parties from accessing it.

Utility Softwares - Help to maintain,

Question 9

What are some different functions of the OS?

Answer 9

Main Function: Communicate with internal & external hardware

1. File Management
- The OS is responsible for file management, the organisation of data into a useable structure.
- It deals with the naming, saving, movement, editing & deletion of data.

2. Multi-Tasking
- The OS helps the CPU carry out multi-tasking by effienctly managing memory and CPU processing time.
- The OS makes sure that the applications don’t overwrite or interfere.

3. User Accounts
- The OS is also responsible for User Account Control. User accounts allow different users to be granted access to specific data.

Question 10

What are some Advantages and Disadvantages of;

A) Client-Server Network
B) Peer-to-Peer

Answer 10

A) Client-Server

1. Advantages

• Easier to keep track of files as they are stored centrally
• Easier to install and update software
• Easier to manage network security

2. Disadvantages

• Expensive to set up and need IT Specialists to Maintain
• Server Dependance - If the server goes down all clients lose access.

B) Peer-to-Peer

1. Advantages

• Easy to maintain ~ You don’t need any expensive hardware.
• No dependence on server

2. Disadvantages

• No centralised management, Backups are also more complicated
• Peer machines are less reliable and data may be lost if one fails.