S3 Data Representation

Question 1

What does a NOT gate look like?
Truth table?

Answer 1

Input —| >o— Output

Input Output
0 1
1 0

Question 2

What does an AND gate look like?
Truth table?

Answer 2

_______________
Input A—| )___Output
Input B—|____ )

A B Output
0 0 0
1 0 0
0 1 0
1 1 1

Question 3

What does an OR gate look like?
Truth table?

Answer 3

_______________
Input A—| \___Output
Input B—|____/

A B Output
0 0 0
1 0 1
0 1 1
1 1 1

Question 4

What does an XOR gate look like?
Truth table?

Answer 4

_________________
Input A—\ \ \___Output
Input B—/ / _____/

A B Output
0 0 0
1 0 1
0 1 1
1 1 0

Question 5

What is a logic gate?

Answer 5

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

Question 6

Symbol for A AND B

Answer 6

A . B

Question 7

Symbol for NOT A

Answer 7

Ā

Question 8

Symbol for A OR B

Answer 8

A + B

Question 9

Symbol for XOR B

Answer 9

A (+) B

Question 10

Convert 300 kB to bits

Answer 10

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

Question 11

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

Answer 11

Bit
Nibble
Byte
Kilobyte
Megabyte
Gigabyte
Terabyte

Question 12

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

Answer 12

10
01

Question 13

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

Answer 13

10
÷4

Question 14

Why do programmers prefer hex?

Answer 14

• 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 15

What is hex 87 in decimal?

Answer 15

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

Question 16

What is decimal 106 in hex?

Answer 16

106 ÷ 16 = 6 r 10
= 6A

Question 17

What’s the largest number in hex?

Answer 17

FF
255

Question 18

Convert binary 1011 1001 to hex

Answer 18

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

Question 19

What is hex 8C in binary?

Answer 19

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

Question 20

Define character set

Answer 20

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

Question 21

Up to what number are ASCII and Unicode the same?

Answer 21

128

Question 22

How many different characters can 7 bit ASCII represent?

Answer 22

128

Question 23

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

Answer 23

7-bits
Extended = 8 bits
Multiple bytes

Question 24

Does Unicode cover all languages?

Answer 24

No
It covers all major languages

Question 25

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

Answer 25

2⁴ = 16 colours

Question 26

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

Answer 26

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

Image size = width x height

Question 27

Define pixel

Answer 27

Picture element, a single point in an image

Question 28

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

Answer 28

Pieces of continuously changing data

Question 29

How do analogue to digital converters work?

Answer 29

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 30

Define sample rate/frequency

Answer 30

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

Question 31

Define sample resolution

Answer 31

The number of bits used to store each sample

Question 32

How do you calculate bit rate?

Answer 32

Bit rate = sample rate x sample resolution

Question 33

How do you calculate the size of a sound file?

Answer 33

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

Or bit rate x seconds

Question 34

Define hertz

Answer 34

Samples per second

Question 35

What are 4 reasons to compress files?

Answer 35

• 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 36

Define Lossy compression

Answer 36

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

Question 37

Define lossless compression

Answer 37

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

Question 38

Pros of lossy compression

Answer 38

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

Question 39

Cons of lossy compression

Answer 39

• cannot be restored to original state