1.2.4 - Data storage

Question 1

What base system is denary?

Answer 1

Base 10
Ranges from 0-255
Uses 0,1,2,3,4,5,6,7,8,9

Question 2

What base system is hexadecimal?

Answer 2

Base 16
Ranges from 00-FF
Uses 0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F

Question 3

What base system is binary?

Answer 3

Base 2
Ranges from 00000000–11111111
Uses 1,0

Question 4

Why do computers use binary?

Answer 4

Binary is used to represent data because computers use transistors which store ‘on’ and ‘off’ using ‘1’ and ‘0’

Question 5

How do you convert from denary to binary? (+vice versa)

Answer 5

Use binary headings:
128,64,32,16,8,4,2,1
(from right to left in ascending order)
Create columns and fill to make the number (+vice versa)

Question 6

How do you add binary together?

Answer 6

Start from the rightmost column and make your way left.
eg. 1001 + 0100 = 1101

Question 7

What is an overflow error?

Answer 7

Occurs when the binary addition succeeds the number of bits available to store the answer.

Question 8

How do you convert denary to hexadecimal? (+ vice versa)

Answer 8

eg. 28 to hexadecimal
First convert the denary number to binary.
Which is 00011100
Then split into 2, 0001 and 1100
These two parts equal 1 and C respectively. (C=12)
Therefore 1C (hex) = 28 (denary)

Question 9

Why might we store data with hexadecimal?

Answer 9

Useful because larger numbers can be represented with fewer digits.
(also easier to understand than binary)

Question 10

What is a binary shift?

Answer 10

A way for computers to perform basic multiplication and division.

Question 11

What does a left shift do?

Answer 11

Multiplies a number by 2 (x2)
eg. left shift of 2 would be a multiplication of 4.

Question 12

What does a right shift do?

Answer 12

Divides a number by 2 (÷2)
eg. a right shift of 2 would divide a number by 4.

Question 13

What is a character set?

Answer 13

A character set is a collection of all the characters that a computer recognises along with their binary codes.

Text is made up of characters.
Each character is assigned its own character code.

Question 14

What are the two main character sets used?

Answer 14

ASCII
Unicode

Question 15

How many bits does ASCII use? And how many characters can that represent?

Answer 15

7 bits.
128 characters. (2^7)

Question 16

How many bits does Extended ASCII use? And how many characters can that represent?

Answer 16

8 bits.
256 characters. (2^8)

Question 17

How many bits does Unicode use? And how many characters can that represent?

Answer 17

Minimum of 16 bits.
Minimum of 65,536 characters.

Question 18

What are the limitations of (extended) ASCII?

Answer 18

Limited number of characters, therefore can only represent the English alphabet and some special characters.
Therefore does not include modern symbols.

Question 19

What is resolution?

Answer 19

The number of pixels an image is made up of.
Calculated by width x height of the image in pixels.

Question 20

What does higher resolution mean?

Answer 20

Better quality of image. It is clearer because more pixels are used to display the image.

Question 21

What is colour depth? (aka bit depth)

Answer 21

Number of bits stored per pixel.

Question 22

How many colours can you represent with a bit/colour depth of x? (eg. 4)

Answer 22

2^x
eg. 2^4 = 16

Question 23

What does higher colour/bit depth mean?

Answer 23

Better quality of image, because more colours can be represented, therefore more alike the original image.

Question 24

How does resolution affect file size?

Answer 24

As the resolution of an image increases, so does the file size,
because the higher the resolution, the more pixels stored in the image,
and the higher the colour depth, the more bits per pixel.

Question 25

What is metadata?

Answer 25

Data about data. Metadata is additional data stored within an image/file. eg. date, location,time,resolution etc.

Question 26

How are sound waves stored and recorded?

Answer 26

Sound waves are analogue. Therefore are stored digitally, using a microphone, and ADC (analog-to-digital converter). You capture the sound by measuring the height (amplitude) of the wave, known as samples, then converted into binary.

Question 27

What is the sample rate?

Answer 27

The number of samples taken per second of wave in Hz. 1Hz is equal to one sample of a sound wave.

Question 28

What is sound bit depth?

Answer 28

The number of bits stored per sample in a sound wave.

Question 29

How does sample rate affect playback quality?

Answer 29

Higher the sample rate, the more detail, therefore better quality and accuracy to original sound.

Question 30

How does sample rate affect the file size?

Answer 30

Higher the sample rate, bigger the file size.

Question 31

How does duration affect playback quality?

Answer 31

Longer duration doesn't affect playback quality directly, however increases file size, therefore many the quality will decrease.

Question 32

How does duration affect the file size?

Answer 32

Longer duration, therefore biggers file size.

Question 33

How does bit depth affect playback quality?

Answer 33

Higher the bit depth, the bigger the range, therefore the better the quality.

Question 34

How does bit depth affect file size?

Answer 34

Higher the bit depth, the more data per sample therefore a larger file size.