3.3 Data Representation

Question 1

Gigabyte (GB)

Answer 1

1000 megabytes

Question 2

A bitmapped graphic uses a colour depth of 3 bits allowing 8 different colours to be used. How many bits are required to represent the colours if an image included 30 colours?

Answer 2

5 bits
[1 bit - 2 colours
2 bits - 4 colours
3 bits - 8 colours
4 bits - 16 colours
5 bits - 32 colours]

Question 3

Character set

Answer 3

All data including characters are represented by binary code. These sets of characters are collections of characters that computers recognise from their binary representation

Question 4

Byte

Answer 4

8 bits

Question 5

Binary

Answer 5

A number base of 2

Question 6

To divide a binary number by 2, shift the digits ONE place to the right.
To divide a binary number by 4, shift the digits TWO places to the right.

Divide 1100 by 2.

Answer 6

128 64 32 16 8 4 2 1
1 1 0 0
1 1 0
[The right-hand digits are lost when they are shifted. To check:
1100 = 12 in denary: 12/2 = 6]

Question 7

Megabyte (MB)

Answer 7

1000 kilobytes

Question 8

What is a binary shift?

Answer 8

Binary numbers are multiplied and divided through a process of shifting. To multiply a number all the digits move to the left. To divide a number all the digits move to the right.

Question 9

Terabyte (TB)

Answer 9

1000 gigabytes

Question 10

Hexadecimal

Answer 10

A number base of 16

Question 11

Nibble

Answer 11

4 bits

Question 12

What is the file size of an image in bytes which is 120pixels x 300 pixels and uses 8 colours? Show your working out.

Answer 12

120 x 300 = 36,000
[8 colours requires 3 bits]
36,000 x 3 = 108,000 bits.

108,000/8 = 13,500 bytes

Question 13

ASCII (American Standard Code for Information Interchange)

Answer 13

Uses 7 bits and represent 128 different characters.The codes are order sequentially, so for example, A is 65 in decimal, B is 66, etc.

Question 14

Unicode

Answer 14

Using extended ASCII the maximum number of 256 characters is far too small to hold every character in other languages, such as Chinese or Arabic. Unicode uses 16 bits, giving a range of over 65,000 characters and more!

Question 15

Kilobyte (kB)

Answer 15

1000 Bytes

Question 16

Bit

Answer 16

Smallest measure of data - 1 or 0

Question 17

Extended ASCII

Answer 17

Uses 8 bits and represents 256 different characters

Question 18

Denary (decimal)

Answer 18

A number base of 10

Question 19

To multiply a binary number by 2, shift the digits ONE place to the left.
To multiply a binary number by 4, shift the digits TWO places to the left.

Multiply 1100 by 2.

Answer 19

128 64 32 16 8 4 2 1
1 1 0 0
1 1 0 0 0
[0 is added to the space when the numbers are shifted. To check:
1100 = 12 in denary: 2 x 12 = 24]

Question 20

What is the number base of the following:
a. Denary
b. Hexadecimal
c. Binary

Answer 20

a. 10 [0,1,2,3,4,5,6,7,8,9]
b. 16 [0,1,2,3,4,5,6,7,8,9, A, B, C, D, E, F,]
c. 2 [0,1]