Data representation

Question 1

Order the following in descending size;
Byte, Petabyte, Megabyte, Gigabyte, Nibble, Terabyte, Kilobyte, Bit

Answer 1

Bit (1 or 0)
Nibble (4)
Byte(8)
Kilobyte(1000B)
Megabyte(1000kB)
Gigabyte(1000MB)
Terabyte(1000GB)
Petabyte(1000TB)

Question 2

Convert 73 to binary

Answer 2

1001001

Question 3

Convert 110110 to denary

Answer 3

54

Question 4

Convert 37 to hexadecimal

Answer 4

25

Question 5

Convert 4F to denary

Answer 5

79

Question 6

Convert 100111 to hexadecimal

Answer 6

27

Question 7

convert 3C to binary

Answer 7

111100

Question 8

2-place shift 1101100 to the right and explain the effect

Answer 8

11011, divided by 4

Question 9

How many characters do ASCII and Unicode represent and what are their differences

Answer 9

ASCII - 2^7 (128), extended ASCII 2^8 (256)
Only some foreign language characters and symbols
Unicode - 2^16(65536)
Includes Chinese, Arabic, Japanese, Greek characters and more

Question 10

How do you calculate colour depth

Answer 10

log ₂(N of colours)

Question 11

State the effect on file size of changing a 4 x 4 pixel from 2 colours to 256

Answer 11

-Each pixel was previously 1 bit, now is 8 (byte)
-The file size would now increase to 16bytes

Question 12

What is resolution

Answer 12

The density of pixels in the same sized area, measures in PPI. A higher PPI will mean smoother edges and improve overall quality

Question 13

What is metadata and state 3 examples

Answer 13

Data about data, eg type of image, image dimensions or colour depty

Question 14

How do computers convert real-world analogue signals, such as sound, to a digital representation

Answer 14

Sound is received by a microphone, then converted by a ADC (Analogue-to-Digital Converter), The ADC samples the amplitude at regular intervals which are then rounded and stored in binary.

Question 15

How do you calculate the size (in bits) of an image file

Answer 15

Colour depth x image height x image width

Question 16

What is sample rate and how does it affect sound file size and quality?

Answer 16

The number of samples taken a second, measured in Hz. Higher Hz means better quality but also increases file size.

Question 17

What is sample resolution and how does it affect sound file size and quality?

Answer 17

The number of bits used to store each sample, higher SR means higher quality but also larger file size

Question 18

What is a sample

Answer 18

A measure of amplitude at a point in time

Question 19

How do you calculate the size of a sound file

Answer 19

Sample rate x Sample size x Sample resolution

Question 20

Why are files compressed?

Answer 20

-Shorten transmittion time
-Reduce amount of storage needed
-Allow large files to be sent as attachments

Question 21

Sort the following into lossy and lossless forms of compression: gif, mp3, mpg, mp2, mov, jpg, wmv, png

Answer 21

Lossy - jpg, mp3, mpg, mp2, wmv
Lossless - png, gif,mov

Question 22

Explain the uses, advantages and disadvantages of lossy compression

Answer 22

•Music streaming, online videos and images
+Small file size = faster transmition and less storage required
-Detail permanently lost

Question 23

Explain the uses, advantages and disadvantages of lossless compression

Answer 23

•Text documents, electronic books
+Original quality is preserved, no data lost
-Less reduction in file size