Systems

Question 1

What are the steps of the fetch-execute cycle?

Answer 1

Step 1 - The processor sets up the address bus with the address xxx.
Step 2 - The processor activates the read line on the control bus/the control unit activates the read line.
Step 3 - An instruction is fetched from the memory location using the databus (and stored in the instruction register).
Step 4 The instruction in the instruction register is then interpreted by the decoder and carried out

Question 2

Name and describe features of a declarative language.

Answer 2

 Use variables which can be applied to existing fact/rules.
 Reduces the need for repetition of facts/ additional lines of code.
 Adds information/meaning based on other facts/rules.
 Establishes relationships between facts/rules.
 Can implement recursion.
OR
Queries
 allow facts/rules to be interrogated

OR
Pattern matching
 allows facts/rules to be matched.

Question 3

Describe an advantage of using Unicode over ASCII, making reference to the number of bits used to represent a character in each format.

Answer 3

Unicode can represent more characters.

 2^16 when compared to ASCII 2^8/2^7
OR
 uses 16 bits compared to 8/7

Question 4

What are the ways to improve performance in modern computer architecture

Answer 4

 Increased use of cache
 Multi-core/number of processors.
 Increase width of data bus.
 Increase clock speed.
 Increase RAM/memory.
 Increase use of solid state.

Question 5

How does the number of processors relate to performance?

Answer 5

Simultaneous execution of instructions/parallel processing.

Question 6

How does increasing the width of the data bus improve performance?

Answer 6

More bits transferred in a single operation.

Question 7

How does increasing the clock speed improve performance?

Answer 7

More fetch-executes per clock pulse

Question 8

How does increasing RAM/memory improve performance?

Answer 8

Reduces the need/faster access to access slower backing storage

Question 9

John has downloaded a new computer game but finds that it does not run on his computer.
State one software reason why the game may not be compatible.

Answer 9

 Version of/out of date operating system.

 Downloaded file is corrupt.

Question 10

John has downloaded a new computer game but finds that it does not run on his computer.
State one hardware reason why the game may not be compatible.

Answer 10

 Insufficient amount of RAM/memory.
 Minimum clock speed not available.
 Version of processor.
 Version of graphics card.

Question 11

Explain the role of the memory management function of the operating system when a user loads the xxx program.

Answer 11

 Tracks/checks available memory.
 Allocates space/addresses in RAM for the function.
 Protects other processes.

Question 12

A stereo sound file lasting 2 minutes with a sample rate of 96 kHz and sample depth of 16 bits is stored on a computer.
Calculate the storage size of the uncompressed sound file.

Answer 12

96000 x 16 x 120 x 2
= 368 640 000/8
= 46 080 000/1024
= 45 000/1024
= 43∙9 Mb

Question 13

Name a function of the operating system and describe one task it will perform when creating an external file.

Answer 13

 File management (1 mark):
o identifies a free space on backing storage to place 
file (1 mark)
OR
o Updates/checks file directory (1 mark)
 Memory management (1 mark): 
o locates data in main memory (1 mark)
OR
o allocates main memory for process (1 mark)
 Input/Output (1 mark): 
o transfer from memory to backing storage (1 mark)
 Resource allocation (1 mark): 
o managing processes and memory (1 mark)

Question 14

Explain how cache improves performance.

Answer 14

 Stores frequently accessed instructions/data
 Faster access times than main memory
 Fewer accesses to slower main memory
 On the same chip as the processor
 Cache is static RAM (faster)

Question 15

Describe how video is compressed using interframe and intraframe compression.

Answer 15

 Interframe saves the differences between frames

 Intraframe compresses a single frame (using RLE or ‘blocking’ shades of colours)

Question 16

Nadia wishes to store a video clip that is 24 frames per second, duration is 95 seconds and has a resolution of 1280 × 720 with a colour depth of 16 bits.
Calculate the storage requirement for the uncompressed video clip. Show all working and express your answer in appropriate units.

Answer 16

9524 128072016

= 3·91387939 Gb

Question 17

Classes and subclasses are key characteristics of object-oriented programming.
Explain why the use of classes and subclasses reduces implementation time for programmers.

Answer 17

Concept of inheritance

Only additional methods and attributes need to be declared for subclasses

Question 18

Pupils access files from a shared folder on their school network server. These files are available for the pupils to open, but only a teacher can edit and save the files to this folder.
Describe how this is implemented.

Answer 18

 Pupils have read only access to this folder (1)

 Teachers have read/write access to this folder

Question 19

State one reason why the increased use of technology has had a negative effect on the environment.

Answer 19

Greater demand
 for raw materials
 transportation of materials
 electricity/energy for manufacture and use

Disposal
 transporting old computers to the dump
 poisonous chemicals contained within computer components can contaminate water and air
 landfill sites

Question 20

What are the advantages of bit-mapped graphics? (3)

Answer 20

• Images can be very realistic
• Pixel editing is allowed – allowing effects such as spray pain, blur, effects and So on.
• Same appearance in all systems regardless of hardware or software.

Question 21

What are the disadvantages of bit-mapped graphics? (4)

Answer 21

• Scaling causes pixelization
• Only the image can be edited.
• Difficult to convert to vector formats.
• File sizes can be large.

Question 22

How do bit-mapped graphics store data?

Answer 22

A bit-mapped graphic stores the data about every single pixel in an image.

Question 23

What are vector graphics?

Answer 23

Vector graphics is a type of graphic that stores the image as a collection of objects including rectangles, ellipses, polygons and lines.

Attributes of each object are stored, such as coordinates, length, breadth, fill colour.

Question 24

What are the disadvantages of vector graphics? (3)

Answer 24

• Difficult to create realistic images.
• Only individual objects can be edited.
• Dependent on output hardware or software appearance & quality may differ.

Question 25

What are the advantages of vector graphics? (4)

Answer 25

• Can be scaled to large sizes, keeping quality.
• Individual objects can be edited.
• Easily converted to bitmap formats
• File size are relatively small

Question 26

What does CPU stand for and what does it do?

Answer 26

Central Processing Unit is the processor is responsible for carrying out the fetch/execute cycle.

This involves accessing memory locations to read and write data, either before or after execution by the processor.

Question 27

How does the number of cores impact processing speed?

Answer 27

Modern processors usually have more that one code. This means that there are actually four processor that make up the CPU. The more cores present, the greater the number of tasks that can be processed simultaneously. This is known as parallel processing.

Question 28

What are registers?

Answer 28

Registers are temporary storages areas in the processor which can be used to hold information

A register is simple a storage location on the processor. Data/Instructions/Addresses that are needed during the fetch/execute cycle are held within registers. Registers offer the fastest access time of any storage location as they are part of the actual processor.

Question 29

There are 5 storage areas in the register. Name them and explain what each does

Answer 29

• Program Counter – the address of the next instruction to be fetched.
• MAR - Memory Address Register – The Memory Address Register holds the address of the next item of data that is needed by the processor.
• Accumulator – results of arithmetic and logic operations
• MDR - The Memory Data Register holds data that is either to be passed to the data bus or has just been received from the data bus.
• Instruction Register – the current instruction being decoded or executed.

Question 30

What are buses?

Answer 30

A bus is a series of lines that connect the processor to another part of the computer’s architecture.

Question 31

How many buses are there and what do they do?

Answer 31

Address Bus – identifies the address of the location in memory that is to be read from or written to. The address bus is uni-directional

Data Bus - Is used to carry data from a memory locations to the processor and vice-versa. The data bus is bi-directional

Control Bus
Each of the control bus lines has a specific function. For example read, write, clock, reset

Question 32

Memory Read - a processor reads instruction from the memory as part of the fetch execute cycle. Describe the 4 steps

Answer 32

1- The processor sets up the address bus with the address of the required memory location
2- The processor activates the READ line on the control bus
3- The contents of the memory location are transferred along the data bus into the processor
4- The instruction is decoded and executed

Question 33

What are the 4 steps of the WRITE Operation

Answer 33

1- The processor sets up the address bus with the address of the required memory location
2- The processor sets up the data bus with the data to be written to memory
3- The processor activates the WRITE line on the control bus
4- The data is transferred along the data bus to the memory location

Question 34

What are the 4 factors affecting system performance?

Answer 34

Number of Cores
Width of Data Bus
Cache
Clock Speed

Question 35

How does using multiple cores affect system performance?

Answer 35

CPUs with multiple cores have more power to run multiple programs at the same time.

Question 36

How does increasing the width of the data bus affect system performance?

Answer 36

By increasing the data bus from 32-bit to 64-bit, the computer can transfer twice as much information at one time. Therefore, increasing the size of the data bus improves performance.

Question 37

What is cache and how can it help improving processor performance?

Answer 37

Cacheis a small amount of memory which is a part of theCPU- closer to the CPU thanRAM. It is used to temporarily holdinstructionsand data that the CPU is likely to reuse.

Although accessing memory is faster then retrieving data from hard disk, processor performance can be improved by using cache memory. Cache is a faster kind of memory which stores copies of data from frequently used memory location. The more cache there is, the more data can be stored closed to the cPU.

Question 38

How does changing clock speed affect system performance?

Answer 38

Clock Speed is how fast the CPU can run. This is measured in MHz or GHz and corresponds with how many instructions the CPU can deal with in a second.
Clock Speed
A faster CPU uses more energy and create more heat. A computer will normally have a maximum clock speed set by default,