1.2 - Data Representation

Question 1

What is a ‘Bit’

Answer 1

A single binary digit, a Zero or a One

Question 2

What is a ‘Nibble’

Answer 2

4 bits

Question 3

What is a ‘Byte’

Answer 3

8 bits

Question 4

What is a ‘Kilobyte’

Answer 4

1,000 bytes or 8,000 bits

Question 5

What is a ‘Megabyte’

Answer 5

1,000,000 bytes

Question 6

What is a ‘Gigabyte’

Answer 6

1,000,000,000 bytes

Question 7

What is a ‘Terabyte’

Answer 7

1,000,000,000,000 bytes

Question 8

What is a ‘Petabyte’

Answer 8

1,000,000,000,000,000 bytes

Question 9

Why is everything in a computer system stored in binary

Answer 9

easier to process
cheaper to manufacture electronic components with just two states
more reliable

Question 10

What can you represent when you combine a series of bits

Answer 10

Any kind of data:

• texts
• images
• sounds
• commands

Question 11

How do you calculate the size of a text file

Answer 11

Bits per character X Number of characters

Question 12

How do you calculate the size of a sound file

Answer 12

Sample rate X duration (s) X Bit depth

Question 13

How do you calculate the size of an image file

Answer 13

Colour depth X Image height (Px) X Image width (Px)

Question 14

What kind of system is binary

Answer 14

Base 2, this means only ones and zeros are used. 1 2 4 8 16 32 64 128

Question 15

Addition - What are the four rules for adding binary numbers

Answer 15

• 0 + 0 = 0
• 0 + 1 = 1
• 1 + 1 = 0 (carry a 1)
• 1 + 1 + 1 = 1 (carry a 1)

Question 16

What is it called when you reach the end and still have to carry a 1

Answer 16

an overflow error, it is when the one we have to carry has gone beyond the capacity of the current storage line.

Question 17

What is the highest number that can be stored in 8-bit binary

Answer 17

255

Question 18

What numbers can be represented in hexadecimal

Answer 18

0-15

Question 19

What are hexadecimal numbers used for?

Answer 19

Representing colours, memory addresses, and Mac Addresses

Question 20

Why are hexadecimal numbers useful

Answer 20

can represent large binary numbers in a smaller number of digits

Question 21

How do you convert denary to hexadecimal

Answer 21

• convert denary to binary
• group binary timeline into two sets of nibbles
• add each of the nibbles where there are 1’s

Question 22

What is numbers 10-15 in hexadecimal

Answer 22

10-A
11-B
12-C
13-D
14-E
15-F

Question 23

What is a binary shift

Answer 23

When you move the binary values to the left or right

Question 24

What is the effect of a one bit left binary shift

Answer 24

Multiplication of 2

Question 25

What is the effect of a one bit right binary shift

Answer 25

Division of 2

Question 26

What happens at a two bit shift

Answer 26

Multiplication of division of 4

Question 27

text - What is a character set?

Answer 27

a defined list of characters recognised by the computer. Each character is represented by a single number

Question 28

text - How is each character represented

Answer 28

by a unique binary number

Question 29

tex - What is ASCII

Answer 29

A 7-bit character set 2^7 characters 128 8th bit is a check digit

Question 30

text - What is Extended ASCII

Answer 30

An 8-bit character set | 2^8 = 256

Question 31

text - What is Unicode

Answer 31

A 24-bit character set 2^24 ≈ 16 million includes every character from every written language

Question 32

images - What two different ways can images be stored

Answer 32

Bitmaps or Vectors

Question 33

images - What are bitmaps constructed of

Answer 33

Pixels

Question 34

images - What decides the number of bits required for each pixel

Answer 34

How many colours are needed

Question 35

images - how is the number of colours calculated

Answer 35

2^n. where n is the number of bits for each pixel

Question 36

images - What is the Colour Depth

Answer 36

The number of bits used to store each pixel

Question 37

images - What is metadata and what does it include

Answer 37

Additional data about the file: file type, date created, author Additional data about the image data: height and width, resolution, colour depth

Question 38

images - What effect does colour depth have on the quality and size of an image file

Answer 38

higher the colour depth, the more colours can be stored, so higher quality. because when you increase the colour depth you are increasing the number of bits used to store each pixel, you are increasing the file size

Question 39

images - What is the resolution of an image?

Answer 39

The number of pixels in an image

Question 40

images - How does resolution effect the quality and file size of an image

Answer 40

higher resolution means more pixels so more detailed image. also it increases the file size

Question 41

images - What colour depth are most photos stored in?

Answer 41

24-bit

Question 42

sound - What is the sample rate

Answer 42

How often per second you record the amplitude of a sound wave. How many samples are taken per second

Question 43

sound - what is the bit depth

Answer 43

number of bits in each sample. the higher the more accurate the sample

Question 44

sound - what is the bit rate

Answer 44

number of bits stored for each second of audio

Question 45

sound - how does the sample rate effect the quality and size of audio

Answer 45

Increases quality as you are recording the amplitude more often so it will be a smoother playback. increases file size as more samples are taken per second

Question 46

sound - how does the bit depth effect the quality and size of audio

Answer 46

Increases quality as more bits are used to store each sample. increases file size as more bits are used to store each sample

Question 47

compression - What does compression do

Answer 47

reduces the number of bits in a file, so making the size of the file smaller

Question 48

compression - Why is compression useful

Answer 48

makes files smaller more data can be stored on a storage device makes data transfer faster

Question 49

compression - lossy compression?

Answer 49

Where some data cannot be recovered. greatly reduces file size. reduces quality of file.

Question 50

compression - lossless compression?

Answer 50

none of the data is lost, its encoded differently. can be turned back to original format. doesn't reduce file size as much as lossy. can be used on all types of data

Question 51

compression - What is lossy compression most suitable for?

Answer 51

images, sound, video

Question 52

compression - What is lossless compression most suitable for?

Answer 52

documents and executable files