Data representation (Paper 1 & 2)

Question 1

Why is hexadecimal often used?

Answer 1

It’s easier for humans to remember hexadecimal numbers as opposed to binary numbers

Question 2

How many bits in a byte?

Answer 2

8 bits = 1 byte

Question 3

How many bytes in a kilobyte?

Answer 3

1000 bytes = 1 kilobytes

Question 4

How many kilobytes in a megabyte?

Answer 4

1000 kilobytes = 1 megabyte

Question 5

How many megabytes in a gigabyte?

Answer 5

1000 megabytes = 1 gigabyte

Question 6

What is a character set?

Answer 6

a defined list of characters recognised by both hardware and software

Question 7

What are two examples of character sets?

Answer 7

ASCII and Unicode

Question 8

What is an advantage of Unicode over ASCII?

Answer 8

Unicode has a wider range of characters

Question 9

What is an advantage of ASCII over Unicode?

Answer 9

ASCII is 7 bit code so it takes up less storage space

Question 10

What is a pixel?

Answer 10

A basic unit of programmable colour

Question 11

What is a bitmap image?

Answer 11

Pixels joined together to form a bitmap image

Question 12

What is colour depth?

Answer 12

Colour depth is the number of bits per pixel

Question 13

Why does sound need to be converted into a digital form to be stored on a computer?

Answer 13

Because analogue sound has an infinite curve on its wavelength so it needs to be converted into a finite curve in order to be stored

Question 14

What is sampling rate?

Answer 14

The number of samples per second of a digital sound

Question 15

What is the sample resolution?

Answer 15

the number of bits used per sample

Question 16

What is the equation for sound file size?

Answer 16

sample rate x sample resolution x number of seconds

Question 17

What is the equation for bitmap image size?

Answer 17

image width x image height x colour depth

Question 18

What is data compression?

Answer 18

Data compression is a way of making data smaller / more compressed

Question 19

What is lossy compression?

Answer 19

When data is compressed by removing some of the data, eg removing pixels from an image

Question 20

What is lossless compression?

Answer 20

When data is compressed but none of the data is removed.

Question 21

What is run length encoding?

Answer 21

A simple form of lossless compression where runs of data are stored in frequencies,

Question 22

How can data be compressed by huffman coding?

Answer 22

It reduces the number of bits per character the more frequently the character is used.