Data Representation

Question 1

Why do computers use binary instead of decimal?

Answer 1

Less arithmetic rules need to be built into the computer
There is either a voltage or no voltage so a drop in voltage doesn’t affect the data being sent
The components inside a computer have only 2 states eg on/off, positive/negative, voltage/no voltage therefore the 2 symbols (1 and 0) used in binary are perfect

Question 2

What 2 codes is text stored as?

Answer 2

ASCII or UNICODE

Question 3

What is an advantage of UNICODE?

Answer 3

Can represent more characters, ASCII limited to 128 characters. so no problem storing characters of non Latin based languages such as Greek, Chinese etc.

Question 4

Disadvantage of UNICODE?

Answer 4

Takes up more memory than ASCII as 16 bits (2 bytes) per character are used.

Question 5

What are integers?

Answer 5

Integers are positive and negative whole numbers (ie NO DECIMAL POINT)

Question 6

What method is used to store negative integers?

Answer 6

twos compliment

Question 7

What is Floating Point Representation?

Answer 7

This is when the number is stored using 2 parts, the MANTISSA and the EXPONENT

Question 8

What is the mantissa?

Answer 8

MANTISSA is a binary fraction between 0 & 1 and is normally stored using 4 bytes. The size of the mantissa affects the ACCURACY of the number.

Question 9

What is the exponent?

Answer 9

The EXPONENT is the power and is normally stored using 1 byte. The size of the exponent affects the RANGE of the numbers available.

Question 10

What 2 ways are graphics stored?

Answer 10

Bitmap or Vector Graphics

Question 11

What is bitmap?

Answer 11

is when the image is stored as a series of pixels and each pixel is stored as a number of bits, depending on the number of colours used.

Question 12

Advantage of bitmap?

Answer 12

Each pixel can be edited individually (perfect for air brushing of photos)

Question 13

Disadvantage of bitmap?

Answer 13

Uses a lot of memory because every pixel including white spaces is saved

Question 14

What is Vector Graphics?

Answer 14

Vector graphics is when each object is stored by its attributes.

e.g – A line may be stored by the following attributes :
( Line – start x, start y, end x, end y, line thickness, line colour, line pattern)

Question 15

Advantages of Vector?

Answer 15

Takes up less memory than bit-mapped.

• Easy to resize, move and alter.
• Images are resolution independent i.e. same image quality regardless of resolution of display or printer.
• Quality of the image is not affected when enlarged.
• Objects can be grouped together and then manipulated as a single object.

Question 16

Disadvantage of Vector?

Answer 16

Cannot be edited at pixel level.

- Limited to mathematical shapes

Question 17

What is bit depth?

Answer 17

This is the number of bits per pixel and it affects the number of colours an image can display.

Question 18

resolution?

Answer 18

This is the number of dot (pixels) per inch

Question 19

What is true colour?

Answer 19

This is when an image had 24 bits per pixels. This means the image can display
16.8 million colours

Question 20

What is an address bus?

Answer 20

This holds the address of where the next instruction has to be read from or written to. It is uni- directional i.e. only goes in one direction from processor to memory

Question 21

What will increasing the size of the address bus do?

Answer 21

The size of the address bus affects the amount of possible memory ( ie the number of addresses) increasing it increases the amount of possible memory. Increasing the size of the AB only improves the speed of the computer if the computer is struggling to run some software at a decent speed or if all of the software cannot be loaded at the one time.

Question 22

What is the data bus?

Answer 22

This allows the movement of data from the processor to memory and vice versa. Increasing the size of the data bus increases the amount of data which can be transferred at the one time therefore it improves the throughput (performance) of a computer.

Question 23

What is the control bus?

Answer 23

This bus is different from the AB + DB because each of the lines work independently ( ie they each have a different function). The lines on the AB + DB all work as a unit and carry data, the CB doesn’t.

Question 24

What is the Control Bus responsible for?

Answer 24

Read/Write lines – Read means read from memory location. Write means write to memory
location.
* Reset – This is a signal into the processor which when activated clears all internal registers,
aborts the current program and starts fetching and executing from a predefined place.

• Clock – This is a pulse which sets the timing for processor activities.
• Interrupt – Can stock the current process but can be ignored e.g no paper in printer.
• Non-Maskable Interrupt – Resets the processor, cannot ignore it e.g power failure.

Question 25

What are the steps of the fetch-execute cycle?

Answer 25

1. set up the AB with the address of the instruction to be carried out. 2. Activate the read line on the CB. 3. Data is transferred onto the DB and into the processor where it is decoded and executed.

Question 26

What are the steps of reading from memory? (buses)

Answer 26

1. set up the AB with the address of the instruction to be carried out. 2. Activate the read line on the CB. 3. Data is transferred onto the DB and into the processor where it is decoded and executed.

Question 27

What are the steps for writing to memory? (buses)

Answer 27

1. set up the AB with address of where data is to be written to. 2. Data is transferred from the processor into the DB. 3. Activate write on CB. 4. Data is transferred from DB to memory location

Question 28

What is the ALU (arithmetic and logic unit) responsible for?

Answer 28

The Alu is responsible for all arithmetic calculations and logical operation involving AND, OR etc

Question 29

What is the control unit responsible for?

Answer 29

The control unit is responsible for fetching, decoding and executing instructions which is the general internal operations of the processor. It controls the movement of data within the processor.

Question 30

What are the registers responsible for?

Answer 30

Registers are temporally storage locations within the processor

Question 31

What will increasing the number of registers do?

Answer 31

The higher the number of registers the better the throughput as internal fetch/execute is faster than having to fetch instruction from memory to the processor.

Question 32

How can you improve computer throughput?

Answer 32

1. Increase the clock speed. The clock rate determines when instructions are fetched & executed, therefore increasing the clock rate increases the amount of data which can be processed per second. 2. Increasing the size of the DB as this increases the amount of data which can be processed per cycle. 3. Adding extra RAM. This helps if your computer is struggling to run some software at a decent speed or if all the software cannot be loaded at the same time especially if it is graphics or multimedia. 4. Uses cache to speed up the transfer of data between memory and the processor

Question 33

What is Cache?

Answer 33

This is an area of memory that can reside (sit in) within the processor or sit between the processor and main memory. This can be accessed very quickly by the CPU & so is a shorter fetch-execute cycle than from processor to the main memory.

Question 34

Explain the difference between interframe and intraframe compression, mentioning which one produces a smaller file size.

Answer 34

Interframe – stores the changes between each frame so produces a smaller file size Intraframe – compresses each frame individually

Question 35

Describe File management and memory management carried out by an OS

Answer 35

File management – manages the use of backing storage by storing files and keeping a record of where they are Memory management – manages main memory and allocates space in RAM to programs

Question 36

What law requires businesses to allow governing bodies to install surveillance software and hardware on their premises.

Answer 36

RIP A

Question 37

Describe 2 ways that businesses could make their use of computers more environmentally friendly.

Answer 37

Reducing electricity use by using energy efficient components/systems Disposal/recycling of old equipment

Question 38

What is serial transmission?

Answer 38

Serial transmission is when data is sent one bit at a time along a straight wire, this is used over long distances because although slower than parallel transmission 'data is not skewed'.

Question 39

What is parallel transmission?

Answer 39

Parallel transmission is when data is sent all at once along several wires.This is only used over short distances e.g connecting a printer to a PC because although faster than serial transmission data can become skewed over long distances.

Question 40

What is a buffer?

Answer 40

- A buffer is an are of memory on a peripheral or on a interface (RAM)

Question 41

What is spooling?

Answer 41

Spooling is when data is stored on fast backing storage ( normally hard disc) and sent to the printer when it becomes available.

Question 42

What is an interface?

Answer 42

An interface is the hardware and software needed for communication between a processor and peripheral devices to compensate for the differences in their speeds, voltages, codes and amounts of data that are transferred at the one time.

Question 43

What are some functions of interfaces?

Answer 43

* status signals – messages sent between the CPU and peripherals confirming whether they are ready to send/receive data or confirming the data has been received. * Data format conversion – changing the data format used by one device into a suitable format for another device. e.g. analogue to digital, serial to parallel etc. * Buffer – To store data temporarily to free up the faster processor. * Device selection – To be able to select the right device.

Question 44

What is the copyright, design and patents act?

Answer 44

You cannot use/copy other peoples materials without their permission.

Question 45

What is the computer misuse act?

Answer 45

This covers 2 things :- hacking and viruses.

Question 46

What is the data protection act?

Answer 46

- Only allowed to see own information. - Must be kept secure and up to date. - Must register with data protection registrar. - Must only use data for purposes that have been registered. - Must only keep for time necessary.

Question 47

What is the function of the user interface?

Answer 47

* Taking commands from input devices (keyboard/mouse). * Interpreting the commands. * Passing them on to the appropriate part of the os to be dealt with.

Question 48

What is the function of file management?

Answer 48

The file management system is responsible for creating, deleting, saving and updating of files and for keeping a directory of where files are stored.

Question 49

What is the function of memory management?

Answer 49

* Checking there is enough RAM to load files. * Allocating a location in RAM for files. * Making sure no 2 programs (files) overlap.

Question 50

What is the function of Kernal (process management)

Answer 50

The main purpose of the kernel is job scheduling ie deciding which task gets the processor and when. Thus it is responsible for the smooth running of the computer. However the kernel is also responsible for keeping a note of the current status of any process when an interrupt is being dealt with.

Question 51

What is the function of input/output?

Answer 51

This is responsible for the actual transfer of data between processor to peripherals and for issuing the appropriate control signals to the peripherals.