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loseless compression
reduces the file size that when it is decompresses all the data is retrieved
use of lossless
code, text, architercural plans
lossy compression
reduces a fee size so that when it is decompressed some of the data has been lost
use of lossy
colour depth reduction, resolution reduction
what is lossy compression ?
removes all none essential information
example of lossy compression
MP3 format file is 10% smaller than original, quiet sounds and high frequencies are cut out
2 examples of lossy compression
voice transmission, mp3
run length encoding and dictionary encoding are 2 types of …
lossless compression
what is lossless compression
records patterning in the data rather than the actual data
run length encoding
compression where data is stored as frequency data pairs.
what is compression?
the process of reducing space needed to store a file
what is a frequency data pair?
single instance of a pattern and how many repetitions of the pattern
con of dictionary encoding
not useful for smaller bodies of text as it requires text in dictionary to be stored.
con of RLE
doesn’t work well for Digital images because the repetitions aren’t frequent.
plaintext
the original data
ciphertext
encrypted data
cipher
encryption method
key
information needed to lock or unlock the data
encryption
transformation of data from one form to another to prevent unwanted 3rd parties from accessing information
symmetric encryption
private key
conditions of symmetric encryption
same key used to encrypt and decrypt text
cons of symmetric encryption
less secure key exchange means that in easily susceptible to interceptions that can lead to cipher text being decrypted.
conditions for asymmetric encryption
uses two seperate but indistinguishable keys; public key for encryption; private key to decrypt.
What is the purpose of compress
Reduce size, download time and storage requirements. Make best use of the bandwidth.
