Data Representation

Question 1

Why is data stored in binary in computer?

Answer 1

The computer uses switches/logic circuits/transistors can only store and process data in two states (high/low) (on/off) (1/0), The binary values represent the current flowing through the circuit, 1 current is on/flowing and 0 is current in off/not flowing.

Question 2

Advantages of Hex

Answer 2

-easier for humans to read and understand -easier for humans to debug -fewer digits so it takes less space on the display.

Question 3

Uses of Hex

Answer 3

-notation for colour in HTML #FF0000 red -Display MAC addresses -Display memory dump/ machine code -display error code

Question 4

Binary Number system

Answer 4

Base 2 system (0-1 values), has units that increase by power 2, more digits for the same value

Question 5

Denary Number system

Answer 5

Base10 (0 to 9 values), has units that increase by power10, less digits than binary for the same value.

Question 6

Hex number system

Answer 6

Base 16, 16 symbols (0 to 9 and A to F), Units that increase by power of 16, least digits than binary and denary for the same value

Question 7

When will overflow error occur?

Answer 7

if value is greater than 255 in an 8-bit register, it occurs when a value outside this limit should be returned.

Question 8

Why does overflow error occur?

Answer 8

A computer/device has a predefined limit that it can represent/store

Question 9

What are the two systems for character representation?

Answer 9

ASCII, Unicode

Question 10

Advantages of ASCII

Answer 10

Character takes only one byte of storage (8 bits)

Question 11

Advantages of Unicode

Answer 11

-Contains many more characters -Unicode allows for a greater range of characters and symbols than ASCII (different languages/emojis)

Question 12

Disadvantages of ASCII

Answer 12

Does not contain a large enough character set for some languages

Question 13

Disadvantages of Unicode

Answer 13

-character takes 2 bytes (16 bits)), -requires more bits per character than ASCII

Question 14

Define Character Set

Answer 14

-All the characters and symbols that can be represented by a computer system. -each character and symbol is assigned a unique binary value

Question 15

Explain how the captured images as converted into digital photo files.

Answer 15

-image is made up of pixels, image has set number of pixels wide by pixels high, each pixel stores one colour, each colour has a unique binary value, the colour/binary value of each pixel is stored in sequence, file contains metadata to identify how the file should be displayed, metadata can be colour depth/resolution, suitable photo file example:JPEG, EXTRA: in coloured high quality images, the amount of binary data needed is much greater to get the correct colour depth in each pixel, in images more pixels used will give a higher quality (resolution)

Question 16

Define Pixel

Answer 16

The smallest component of an image

Question 17

Define photo resolution

Answer 17

The number of pixels in an image

Question 18

Define photo colour depth

Answer 18

The number of bits used to represent each colour

Question 19

How to increase file size and quality of an image

Answer 19

increase resolution and colour depth

Question 20

Explain how the recorded sounds are converted to digital photo files

Answer 20

sampling is used by recording the amplitude the amplitude of the sound waves at regular time intervals, the value of the sample is recorded as a binary number, increasing the sampling rate means more samples will be used (and the time intervals will be closer) and the sound track quality will be higher

Question 21

Define sound Sample Rate

Answer 21

numbers of samples taken in a second

Question 22

Define sound Sample resolution

Answer 22

Number of bits per sample

Question 23

What increase the accuracy of the recording

Answer 23

file size increases as sample rate and resolution increases as accuracy increases

Question 24

Why do we compress data

Answer 24

smaller file size(less storage space needed), less bandwidth required, faster transmission(quicker to upload and download)

Question 25

Define data compression

Answer 25

reducing the file size

Question 26

Types of compression

Answer 26

lossy compression and lossless compression

Question 27

Define Lossy compression

Answer 27

-some data will be lost permanently and original file cannot be recreated, -removing details from the image that should go unnoticed and will not affect the quality too much

Question 28

Define Lossless Compression

Answer 28

when decompressed, the original file is restored with no loss of data as no data is permanently removed. Process: Run Length Encoding (RLE)

Question 29

When is Lossy compression used?

Answer 29

For multimedia such as audio, video and image files

Question 30

When is lossless compression used?

Answer 30

When it is essential that no data is lost or discarded (text)

Question 31

How is a music file compressed by lossy compression

Answer 31

-a lossy compression algorithm is used, (define lossy compression: -some data will be lost permanently and original file cannot be recreated, -removing details from the image that should go unnoticed and will not affect the quality too much),- uses perceptual music shaping: (-removing noises that may not be heard by human ear,-if two sounds are playing at the same time, the softer sound is removed) -reduces sampling rate and sampling resolution.

Question 32

How is a music file compressed by lossless compression

Answer 32

-a lossless compression algorithm is used, -define lossless compression (when decompressed, the original file is restored with no loss of data as no data is permanently removed. Process: Run Length Encoding (RLE)),- repeated patterns of notes are identified and the pattern is stored only once along with how many times it is repeated

Question 33

How is an image compressed by lossy compression

Answer 33

-a lossy compression algorithm is used,- (define lossy compression: -some data will be lost permanently and original file cannot be recreated, -removing details from the image that should go unnoticed and will not affect the quality too much),- colour depth can be reduced by reducing the number of bits required for each pixel/colour, -resolution can be reduced by reducing the number of pixels

Question 34

How is an image compressed by lossless compression

Answer 34

-a lossless compression algorithm is used, -define lossless compression (when decompressed, the original file is restored with no loss of data as no data is permanently removed. Process: Run Length Encoding (RLE)),- repeating patterns (colour patterns) in the image/data are identified and the number of times the pattern appears is stored, -an index/dictionary of pixels is created, the number of times a pixel is repeated in a row, is stored.

Question 35

How is a video compressed by lossy compression

Answer 35

-a lossy compression algorithm is used,- (define lossy compression: -some data will be lost permanently and original file cannot be recreated, -removing details from the image that should go unnoticed and will not affect the quality too much),-removes details that human eye/ear may not see/hear, -reduce colour depth, -reduce image resolution,- reduces sample rate of sound, -reduces the sample resolution of sound

Question 36

How can the size of the text file be reduced?

Answer 36

-a lossless compression algorithm is used, -define lossless compression (when decompressed, the original file is restored with no loss of data as no data is permanently removed. Process: Run Length Encoding (RLE)), repeated words are identified and are indexed/ put into a table,- repeated words are relaced with their index,-the positions of the repeated words are stored in the table,-the number of times the word appears is stored in the table.