Data Representation

Question 1

How many inputs and outputs do NOT gates have?

Answer 1

One Input

One Output

Question 2

Put these units in order of size (smallest to largest):

Terabyte, Byte, Kilobyte, Gigabyte, Megabyte

Answer 2

Byte, Kilobyte, Megabyte, Gigabyte, Terabyte

Question 3

Convert 17 (decimal) to binary

Answer 3

10001

Question 4

Convert 17 (decimal) to hexadecimal

Answer 4

11

Question 5

Convert 0011 1000 (binary) to decimal

Answer 5

56

Question 6

What effect do left and right shifts have on binary numbers?

Answer 6

Left shifts multiply a binary number. For every place shifted left, the number is doubled
Right shifts divide a binary number. For every place shifted right, the number is halved

Question 7

Convert 1001 1111 (binary) to decimal

Answer 7

159

Question 8

Convert 1001 1111 (binary) to hexadecimal

Answer 8

9F

Question 9

Convert 10 1011 (binary) to decimal

Answer 9

43

Question 10

Convert 10 1011 (binary) to hexadecimal

Answer 10

2B

Question 11

Convert 4A (hexadecimal) to decimal

Answer 11

74

Question 12

Convert 4A (hexadecimal) to binary

Answer 12

1001010

Question 13

Convert 75 (hexadecimal) to decimal

Answer 13

117

Question 14

Convert 75 (hexadecimal) to binary

Answer 14

1110101

Question 15

Convert 148 (decimal) to binary

Answer 15

10010100

Question 16

Convert 148 (decimal) to hexadecimal

Answer 16

94

Question 17

Convert 240 (decimal) to binary

Answer 17

11110000

Question 18

Convert 240 (decimal) to hexadecimal

Answer 18

F0

Question 19

Convert BD9 (hexadecimal) to decimal

Answer 19

3033

Question 20

Convert BD9 (hexadecimal) to binary

Answer 20

101111011001

Question 21

Encode this string using run-length encoding:

PPPPQQRRRSSSSSSPPPPPQQQ

Answer 21

(4,P), (2,Q), (3,R), (6,S), (5,P), (3,Q)

Question 22

Calculate the number of bits need to store this string if it was encoded with ASCII:
PPPPQQRRRSSSSSSPPPPPQQQ

Answer 22

23 x 8 = 184 bits

Question 23

Why do programmers prefer hexadecimal over binary and decimal?

Answer 23

It is simpler to remember large numbers in hex - they’re far shorter than binary numbers

Due to them being shorter, there’s less chance of input errors

It’s easier to convert between binary and hex than binary and decimal

Question 24

What is the definition of a character set?

Answer 24

A collection of characters that a computer recognises from their binary representation

Question 25

What are the four types of characters that are included in a character set?

Answer 25

1. Uppercase letters 2. Lowercase letters 3. Digits 4. Symbols

Question 26

What are the two main character sets?

Answer 26

ASCII | Unicode

Question 27

Define the term pixel?

Answer 27

One of the individual units that make up an image

Question 28

Define the term bitmap?

Answer 28

An image made up of pixels

Question 29

Define the term colour depth?

Answer 29

The number of bits used for each pixel

Question 30

Define the term image resolution

Answer 30

The number of pixels in the image

Question 31

What are the effects of choosing a greater image resolution or colour depth for an image?

Answer 31

Using a grater image resolution or colour depth mean that there are more bits in the image. This can give a higher quality image, but also increases the file size.

Question 32

How does audio sampling work?

Answer 32

1. Sound is recorded by a microphone as an analogue signal 2. The analogue signals are converted into digital data by analogue to digital converters so that the computers can read and store sound files

Question 33

Define the term sample rate

Answer 33

How many samples you take in a second

Question 34

What happens when you increase the sample rate?

Answer 34

Increasing the sample rate means the analogue recording is sampled more often. The sampled sound will be better quality and will more closely match the orignal recording. However, increasing the sample rate will also increase the file size

Question 35

Define the term sample resolution

Answer 35

The number of bits available for each sample

Question 36

What happens when you increase the sample resolution?

Answer 36

Increasing the sample resolution means the digital file picks up quieter sounds, even if they’re happening at the same time as louder ones. This will also result in a sampled sound that is closer to the quality of the orignal recording. However, increasing the sample resolution will increase the file size

Question 37

Why might you want to compress data?

Answer 37

Smaller files take up less storage space on a device Streaming and downloading files from the internet is quicker as they take up less bandwidth It allows webpages to loads more quickly in web browsers Email services normally have restrictions on the size of the attachment you can send - compressing the file allows you to send the same content with a much smaller file size.

Question 38

What is the difference between lossy compression and lossless compression?

Answer 38

Lossy compression works by permanently removing data from the file - this limits the number of bits the file needs and so reduces its size Lossless compression makes the files smaller by temporarily removing data to store the file and then restores it to its orignal state when its opened

Question 39

Why might you want to use lossy compression?

Answer 39

Greatly reduced file size, meaning more files can be stored Takes up less bandwidth so can be downloaded and streamed more quickly Commonly used - lots of software can read lossy files

Question 40

Why might you want to use lossless compression?

Answer 40

Data is only removed temporarily so there is no reduction in quality - the compressed file should look or sound like the original Can be decompressed - turned back into the original Can be used on text and software files

Question 41

What is the formula used to calculate the size of a sound file

Answer 41

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

Question 42

Define the term number base

Answer 42

A number base is the number of digits or combination of digits that a system of counting uses to represent numbers

Question 43

Explain the purpose of hexadecimal

Answer 43

It can be used to write large binary numbers in just a few digits

Question 44

Describe the ASCII and Unicode character sets

Answer 44

ASCII is a character encoding that uses numeric codes to represent characters Unicode is a universal character encoding standard that assigns a code to every character and symbol in every language in the world