1.2 Memory & Storage Part 2

Question 1

What is a character set + examples&how many bits

Answer 1

Collections of characters that a computer recognises from their binary representation.

E.g ASCII- 7 bits, Extended ASCII- 8 bits, Unicode- 16 bits

Question 2

Give the calculation for file size of an image

Answer 2

File size = resolution x colour depth

Resolution- width x height
Colour depth- number of bits used for each pixel
2 to the power of 2bits = 4 colours
2 to the power of 3bits = 8 colours

Question 3

What is metadata

Answer 3

Information stored in an image file about the picture

E.g resolution, colour depth, file format

Question 4

Give the calculation for file size of a sound file

Answer 4

File size = sample rate x bit depth x duration

Sample rate- number of samples stored per second
Bit depth- number of bits stored per sample

Amplitude of a wave is sampled

Question 5

What’s a bitmap and vector

Answer 5

Bitmap- constructed from pixels
Vector- mathematics used to draw shapes are stored

Question 6

What’s lossy compression

Answer 6

Data is permanently deleted to reduce number of bits in the file so the size is lower. Algorithms are used to guess removed content

Greatly reduces file size but reduces image/sound quality and cannot be recovered.

Suitable for images, sound and video but cannot be used on text files and executable files.

Question 7

What’s lossless compression

Answer 7

Finds groups of repeating data and records it on,h once and how many times it’s repeated so no data is lost and it can be recovered.

It can be used on all file types but is less affective than lossy at reducing file size. Most suitable for documents and executable files.