1.3 storage and compression

Question 1

how is storage measured (units?)

Answer 1

bit (b)
nibble
byte (B)
kibibyte (KiB)
gibibyte (GiB)
tebibyte (TiB)
pebibyte (PiB)
exbibyte (EiB)

Question 1

how is file size of an image file calculated

Answer 1

resolution (pixels) * colour depth (bits)

Question 2

how is file size of sound file calculated

Answer 2

sample rate (Hz) * resolution (bits) * length of track (s)

Question 3

benefits of compression

Answer 3

• less storage space required
• less bandwidth required (faster loading)
• shorter transmission time

Question 4

what are the types of compression

Answer 4

lossy and lossless

Question 5

how does lossy compression work

Answer 5

reduces file size by permanently removing data from original source file

eg reduce resolution/colour depth, reduce sample rate/resolution

Question 6

how does lossless compression work

Answer 6

reduce file size without permanent loss of data

compression algorithm used, eg RLE (finding groups of repeating data and only storing them once)

Question 7

disadvantage of lossy compression

Answer 7

lower quality files as some data lost

Question 8

disadvantage of lossless compression

Answer 8

if file has little or no repeated data, compression larger than original

Question 9

what are raw files

Answer 9

files with no compression