S3 Data Representation

Question 1

What is a logic gate?

Answer 1

Circuits built into computer chips
- they receive binary data
- apply a Boolean operation
- output a binary resume

Question 2

Symbol for A AND B

Answer 2

A . B

Question 3

Symbol for NOT A

Answer 3

Ā

Question 4

Symbol for A OR B

Answer 4

A + B

Question 5

Symbol for XOR B

Answer 5

A (+) B

Question 6

Convert 300 kB to bits

Answer 6

300kB = 300 x 1000 = 300 000 bytes
300 000 bytes = 300 000 x 8
=2 400 000 bits

Question 7

What is the order of the sizes of bits and bytes?

Answer 7

Bit
Nibble
Byte
Kilobyte
Megabyte
Gigabyte
Terabyte

Question 8

What is 1+1 in binary?
What is 1+0 in binary?

Answer 8

10
01

Question 9

What is 1011 after having a 2 place shift left?
What is the effect of this shift?

Answer 9

10
÷4

Question 10

Why do programmers prefer hex?

Answer 10

• simpler to remember larger numbers
• Due to hex being shorter, less chance of input errors
• easier to convert between binary and hex than binary and decimal

Question 11

What is hex 87 in decimal?

Answer 11

8 x 16 = 128
7 x 1 = 7
128 + 7 = 135

Question 12

What is decimal 106 in hex?

Answer 12

106 ÷ 16 = 6 r 10
= 6A

Question 13

What’s the largest number in hex?

Answer 13

FF
255

Question 14

Convert binary 1011 1001 to hex

Answer 14

1011 1001
1011 = 11(dec) = B
1001 = 9
=B9

Question 15

What is hex 8C in binary?

Answer 15

8 = 1000(binary)
C = 12(dec) = 1100
= 1000 1100

Question 16

Define character set

Answer 16

Collections of characters that a computer recognises from their binary representation.

Question 17

Up to what number are ASCII and Unicode the same?

Answer 17

128

Question 18

How many different characters can 7 bit ASCII represent?

Answer 18

128

Question 19

How many bits are used per character in ASCII? What about Unicode?

Answer 19

7-bits
Extended = 8 bits
Multiple bytes

Question 20

Does Unicode cover all languages?

Answer 20

No
It covers all major languages

Question 21

What is the total amount of colours for a 4 bit image?

Answer 21

2⁴ = 16 colours

Question 22

How do you work out the file size of an image? (How many bits it will take up)

Answer 22

File size (in bits) = image size x colour depth

Image size = width x height

Question 23

Define pixel

Answer 23

Picture element, a single point in an image

Question 24

Sound waves are recorded as an analogue signal. What is an analogue signal?

Answer 24

Pieces of continuously changing data

Question 25

How do analogue to digital converters work?

Answer 25

1) Analogue sound is received by a microphone
2) This is converted to an electrical analogue signal
3) The signal amplitude is sampled at regular intervals
4) The values are rounded to a level
5) The values are stored as a series of binary numbers

Question 26

Define sample rate/frequency

Answer 26

How many samples you take per second(Hz/kHz)

Question 27

Define sample resolution

Answer 27

The number of bits used to store each sample

Question 28

How do you calculate bit rate?

Answer 28

Bit rate = sample rate x sample resolution

Question 29

How do you calculate the size of a sound file?

Answer 29

File size (bits) = Sample rate (Hz) x sample resolution x seconds

Or bit rate x seconds

Question 30

Define hertz

Answer 30

Samples per second

Question 31

What are 4 reasons to compress files?

Answer 31

• less storage space
• streaming and downloading files from the internet faster as they take up less bandwidth
• web pages load faster
• emails have restrictions on file size.

Question 32

Define Lossy compression

Answer 32

Permanently removing data from a file to reduce it’s size.

Question 33

Define lossless compression

Answer 33

Temporarily removing data to store a file, then returning it to it’s original state when opened

Question 34

Pros of lossy compression

Answer 34

• Greatly reduced file size
• Takes up less bandwidth
• Commonly used, most software can read

Question 35

Cons of lossy compression

Answer 35

• cannot be restored to original state