Memory And Storage (part 2)

Question 1

How many bits are in a byte?

Answer 1

8

Question 2

How many bytes are in a kilobyte?

Answer 2

1000

Question 3

How would you calculate the file size of a text file?

Answer 3

Number of bits per character x number of characters

Question 4

How would you calculate the file size of an audio file?

Answer 4

Sample rate x duration (s) x bit depth

Question 5

How would you calculate the file size of an image?

Answer 5

Colour depth x image width (px) x image height (px)

Question 6

What do binary shifts do?

Answer 6

Divide or multiply the number

Question 7

What are the problems with binary shifts?

Answer 7

• Can create an overflow
• Number is rounded and therefore loses precision

Question 8

What is metadata?

Answer 8

Additional information stored about an image eg. height, width

Question 9

What is a character set?

Answer 9

A defined list of characters recognised by the computer

Question 10

Give 2 examples of character sets

Answer 10

• ASCII
• UNICODE

Question 11

What is ASCII?

Answer 11

Early 7 bit character set which was later extended to 8 bits

Question 12

What is UNICODE?

Answer 12

The modern most commonly used character set that uses 24 bits

Question 13

How many characters can be used in a 7 bit character set?

Answer 13

2⁷ = 128

Question 14

How are images represented on a computer?

Answer 14

As a series of pixels which is represented in binary, each pixel has a specific colour and each colour has a specific code

Question 15

What effect does increasing the colour depth have on an image?

Answer 15

• Increased file size
• Increased quality

Question 16

What effect does increasing the resolution have on the image?

Answer 16

• Increased file size
• Increased image quality

Question 17

What is colour depth?

Answer 17

The number of bits for each pixel

Question 18

What factors affect the quality of digitally converted sound?

Answer 18

• Sample rate
• Bit depth

Question 19

What is sample rate?

Answer 19

How often you record the amplitude of the sound wave

Question 20

How is sound converted into a file?

Answer 20

The sound is sampled by measuring the height of the wave at set intervals and then converted into binary

Question 21

What is sample rate measured in?

Answer 21

Hertz (Hz)

Question 22

What effect does increasing the sample rate have on the file?

Answer 22

• Higher quality sound
• Larger file size

Question 23

What is the bit depth?

Answer 23

The number of bits used for each sample

Question 24

What does compression do?

Answer 24

Reduce the size of a file so it takes up less space on a storage device

Question 25

Why would you need compression?

Answer 25

• To free up storage, allowing more data to be stored
• Quicker download and transfer speeds (allowing streaming)

Question 26

What are the 2 different compression types?

Answer 26

• Lossy
• Lossless

Question 27

What is lossy compression?

Answer 27

Compression of files when the colour depth and/or resolution is reduced

Question 28

What are the advantages of lossy compression?

Answer 28

• Significantly reduces file size
• Hard to notice change in image quality

Question 29

Name a disadvantage of lossy compression?

Answer 29

Lower image quality as there is less detail

Question 30

What is lossless compression?

Answer 30

Compression when the way the image is encoded is changed but the image itself stays the same

Question 31

What are the advantages of lossless compression?

Answer 31

• No detail is lost
• Reduces file size without losing any data

Question 32

Name a disadvantage of lossless compression?

Answer 32

• Only works with images that have a lot of repeating colour eg. cartoons
• Doesn’t reduce file size as much as lossy compression