Unit 1: Data Representation

Question 1

Convert 2A from hex to denary

Answer 1

16x2+10=42

Question 2

How do you perform two’s complement in binary?

Answer 2

Reverse all 1s and 0s and then add 1.

Question 3

Convert denary 14 to hexadecimal.

Answer 3

The scale is 0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F, etc.

So therefore the answer is E

Question 4

What is A32F in binary?

Answer 4

Each hex digit is used for one nibble (four bits)

Therefore A32F = 1010 0011 0010 1111

What is hex F27B in binary?

What is hex ABCD in binary?

Question 5

What is hex F27B in binary?

Answer 5

1111 0010 0111 1011

Question 6

What are the advantages of Hex?

Answer 6

It is easier for humans to understand as it is a shorter
representation of the binary

Hex values are also easier to remember and enter

People are less likely to make an error with fewer digits

Question 7

What is an overflow error?

Answer 7

When the result of an addition is too large for the
number of bits the computer works with, there will be an overflow error

Question 8

What is the effect of a binary shift to the right?

Answer 8

Division

Question 9

What is the effect of a binary shift to the left?

Answer 9

Multiplication

Question 10

What is sample rate in audio files?

Answer 10

Number taken of samples per second(measured in hz)

Question 11

What is sample resolution?

Answer 11

The number of bits (audio bit depth) used to record
each sample

Question 12

How do you calculate file size of audio files?(in bits)

Answer 12

File size (bits) = sample rate × resolution × duration

Question 13

What is image resolution?

Answer 13

Image resolution is the number of pixels in the image

Question 14

How do you increase the number of colours in an image?

Answer 14

More bits per pixel =
more colour combinations

1 bit = 2 Colours

2 bits = 4 Colours

3 bits = 8 Colours

4 bits = 16 Colours

Question 15

Bit depth: How many bits per pixel
required for 256 colours?

Answer 15

2^8=256
8 bits per pixel

Question 16

How do you calculate the file size of an image?

Answer 16

image width x image height x colour depth (in bits)

Question 17

Describe the effect of reducing the resolution and colour depth of an image.

Answer 17

The file size would be reduced since the there is less data therefore the file would be more compact. The colours would lose their detail and the quality would deteriorate, the same would go for the resolution since you are lowering the amount of pixels in the file.

Question 18

What is compression?

Answer 18

Compression is reducing the the size of a file so that it takes up less space on secondary storage.

Question 19

What is the difference between lossy and lossless compression?

Answer 19

Lossy compression permanently loses some data while lossless compression does not lose any data

Question 20

What is Run Length Encoding?

Answer 20

Run-length encoding (RLE) is a form of data compression that condenses identical elements into a single value with a count

Question 21

Use RLE to shorten this piece of code assuming 1=white and 0 =black

1111000000000000

Answer 21

Using RLE, the row could be represented as 4 ‘1’s
and 12 ‘0’s or 4 1 12 0

Question 22

Describe 2 advantages of compression

Answer 22

Smaller files = fewer packets = faster transmission time

Quicker to complete transmission

Reduces traffic over the Internet

Reduces download times of video, sound (including
speech used for VOIP systems) and image files

Streaming is also possible as the data can be sent as fast as the
rate it is played

Images inside web pages appear faster

Reduces space on disk / servers