Data Representation (Year 10)

Question 1

How many bits in one byte

Answer 1

8

Question 2

How many bits in a nibble

Answer 2

4

Question 3

How many states does binary have

Answer 3

2, either 1 or 0

Question 4

Memory from lowest to highest

Answer 4

Lowest - Kilobyte
Megabyte
Gigabyte
Terabyte
Highest - Petabyte

Question 5

One byte in each of the units

Answer 5

1 kilobyte = 1000bytes
1 megabyte = 1000 000 bytes
1 gigabyte = 1000 000 000 bytes
1 terabyte= 100 000 000 000bytes
1 petabyte= 1000 000 000 000 000bytes

Question 6

Generally what is the memory of secondary storage measured in

Answer 6

Terabytes

Question 7

What base is binary

Answer 7

Base 2

So it is arranged:

The highest binary number would be 255, which is 11111111

Question 8

What are the rules for binary addition

Answer 8

Whenever 1+1 write 0 and carry 1
Whenever 1+1+1 write 1 and carry 1
Whenever 1+0 write 1 carry 0

Question 9

What is the effect in binary shifts if we shift to the left

Answer 9

The original number is multiplied by the shift as a power of 2

Eg

00001111 ————————————-> 00111100
15. Multiplied by 2^2. 60

The shift was 2, so it was multiplied by 2^2

Question 10

What happens when we shift to the right

Answer 10

Shifting to the right has the affect of /2 the number
Eg of a shift was 3 to the right it would be the original number / 2^3
-> So it Would be original number/8

01110000 —————————————> 00001110
112. Shift 3 so divide by 2^3. 14

Question 11

Why do we use hexadecimal

Answer 11

Strings like 01011011 are really hard to remember, so to fix this we use hexadecimal, where each nibble (4 bits) represents a character

Question 12

Smallest 4 bit number

Answer 12

0000

Question 13

Largest 4 bit number

Answer 13

1111

Question 14

How many different combinations can you have with just 4 bits

Answer 14

16

Question 15

What does 1111 represent in hexadecimal

Answer 15

The letter F

Question 16

What happens after the letter F Im hexadecimal (it is the largest nibble value)

Answer 16

Then we go back to using full bytes.

Eg after F would be 00010000= 1 0 in hex

Question 17

How to convert from decimal to hex

Answer 17

Hexadecimal uses base 16

Eg converting 182 to hex

Do 182/16

= 11 remainder 6

Then use a table to write each induvidual number in hex

11 = B
6 = 6

Therefore 182 = B6 in hex

You could also convert 182 to binary then use the binary for hex but that takes longer

Question 18

Convert hex to decimal

Answer 18

Just like binary, hex is written like

Etc …. 16^5. 16^4. 16^3. 16^2. 16^1. 16^0

So if our hex was 23F, then you woukd do

16^2 x 2
16^1 x 3
16^0 x 15 (*F is 15 numerically)

512+48+15=575

So 23F is 573 in decimal

Question 19

2 advantages of hex

Answer 19

Expressed more compactly

Easier to understand

Question 20

What does ASCII stand for

Answer 20

American Standard Code for Information Interchange

Question 21

How many bits does regular ASCII use

Answer 21

7 bits to code each character

Question 22

Biggest value that can be held in ASCII

Answer 22

127 (decimal) or 1111111

Therefore 128 characters can be represented (0-127)

Question 23

How to represent a in regular ASCJI

Answer 23

97

Question 24

How to represent A in regular ASCJI

Answer 24

65

Question 25

What is extended ascii

Answer 25

Uses 8 bits for each character

Question 26

What does extended ascii do

Answer 26

Gives us 128 extra characters we can represent, bringing us to 256 total

Question 27

What is Unicode

Answer 27

Unicode is a state that uses 8-32 bits to represent many more unique characters than ascii because of the larger number of bits available to store the code The same codes as ASCII are used up to 127

Question 28

What are pixels

Answer 28

Small elements that photos are broken down into, that have an independent colour set

Question 29

What happens if the size of a picture is increased

Answer 29

-> More pixels will need to be stored -> increases file size

Question 30

What is colour/bit depth

Answer 30

Number of bits per pixel -> it is always expressed as a power of 2 How many bits represent each pixel

Question 31

What happens as colour depth increases

Answer 31

More bits are used to represent each colour meaning overall file size increases

Question 32

Genral,y what is the size of an image with a bit depth of 1

Answer 32

60kb

Question 33

What is the size of an image

Answer 33

The number if pixels it is made up of

Question 34

What happens if there is a higher PPI (pixels per inch)

Answer 34

The image will look sharper, but will have a much larger file size This is because there are more pixels in the same physical space meaning the size of the pixels decreases and there are more of them

Question 35

What is pixel density

Answer 35

the number of individual pixels packed into a given physical area Measured in pixel per inch Used to describe the resolution of the image

Question 36

How to calculate fuel size in bits

Answer 36

Image width x image height x colour depth

Question 37

How to calculate fuel size in bytes

Answer 37

(Image width x image height x colour depth)/8

Question 38

What does analogue mean when describing sound waves

Answer 38

Means they are continually changing

Question 39

What is a sample when measuring sound

Answer 39

It is a measure of amplitude of the wave at a point in time

Question 40

What does raw accuracy of a sojnd conversion depend on

Answer 40

-> sample resolution -> sample rate

Question 41

What is the sample resolution

Answer 41

The number of bits used to store each sample

Question 42

What is sample rate

Answer 42

The frequency at which you record the amplitude of the sound, ie the number if samples per second The more frequently the sound is sampled, the smoother and better quality it is

Question 44

How to calculate the size of a sound file

Answer 44

Sample rate x sample res x no of seconds

Question 45

Why is compression used

Answer 45

To reduce the amount of storage needed on a computer to save files To allow files to be transmitted by email and compressing them can help send Allow file to be transmitted in less time

Question 46

What is lossy compression?

Answer 46

It is a data including method by files are compressed by removing some of the data For example can be stored using less colour meaning few bits are needed which helps reduce the file size But this means that some things are lost from the original file, so it’s less true to the original

Question 47

What is lossless compression?

Answer 47

Is the data compression method where they are compressed in a way that no data is lost and the file remains true to the original

Question 48

What is run length encoding?

Answer 48

RLE is a type of lossless data compression where sequences of data with the same values are stored using data pairs

Question 49

Disadvantages of RLE

Answer 49

In files that contain less runs, it might actually increase the storage size if you use run length encoding

Question 50

What are runs

Answer 50

Sequences of data

Question 51

Examples of lossy data types

Answer 51

JPEG = it’s good for photos and has a colour depth to 24 meaning there are 16.7 million colours MP3 = normally used to store music or downloading it from the Internet

Question 52

Examples of lossless data types

Answer 52

Graphic interchange format (GIF) - it’s good for images with the large areas of solid colour

Question 53

What is Hoffman coding?

Answer 53

It is a compression technique used to reduce the number of bits used to represent each letter Letters that appear more frequently use less bits to represent them It uses a structure called a binary tree which consists of a root node a number of smaller nodes and branches

Question 54

How to read a binary tree

Answer 54

Each branch will have a value of either zero or one0 will always be the left most branch while one will be on the right

Question 55

Describe how binary is used to represent data in computers

Answer 55

Computers use logic circuits They use high or low voltages to store 1 and 0