1.3 Data storage and compression Flashcards
bit
Short for binary digit.
It is the smallest unit of data that is represented in a computer.
It has a single binary value 1 or 0
nibble
equals to 4 bits (half a byte)
byte
equivalent to 8 bits
1 kibibyte (KiB)
(2^10) equivalent to 1024 bytes
mebibyte (MiB)
2^20 equivalent to 1024 x 1024 (1024^2) bytes
gibibyte (GiB)
2^30 equivalent to 1024 x 1024 x 1024 (1024^3) bytes
1 tebibyte TiB
2^40 equivalent to 1024 x 1024 x 1024 x 1024 bytes
1 pebibyte PiB
equal to 2^50 bytes
exbibyte (EiB)
EiB is equal to 2^60 bytes
acronym for memory size
KMGTPE
King Mark Gave Ten Powerful Elephants”
King = KiB = 2^10 bytes
Mark = MiB = 2^20 bytes
Gave = GiB = 2^30 bytes
Ten = TiB = 2^40 bytes
Powerful = PiB = 2^50 bytes
Elephants = EiB = 2^60 bytes
as u go down divide
The file size of an image is calculated as
image resolution (in pixels) × colour depth (in bits)
The size of a mono sound file is calculated as
sample rate (in Hz) × sample resolution (in bits) × length of sample (in seconds)
For a stereo sound file
you would then multiply the result by two.
Benefits of reducing the size of a file
- reduces storage space required
- reduce transmission time
- less bandwidth required for transmission
There are 2 types of compression:
lossy and lossless file compression
Lossy Compression:
-Lossy compression reduces the file size by permanently removing some data from the file e.g reducing image resolution or colour depth, reducing sample rate or sample resolution
mp3- sound, mp4- video, jpeg- image
Lossless
A compression algorithm is used to reduces the file size without permanently removing any data
Run length encoding (RLE)
replaces sequences of repeated characters with a code that represents the character and the number of times it is repeated
How image files are compressed (lossy)
- a compression algorithm is used
- colour depth may be reduced (colours that the human eye cannot see are removed)
- image resolution may be reduced
How sound files are compressed (lossy)
- a compression algorithm is used
- sounds that cannot be heard by the human ear are removed
- sample rate may be reduced
- sample resolution may be reduced
How text files are compressed (lossless)
- a compression algorithm called run length encoding (RLE) is used
- no data is removed
- repeating characters patterns are identified and indexed
differences
lossless file size will be larger so it may take longer to upload
