Flashcards
Compression
Cards in this deck (5)
- 1What is Compression and its 2 Types?> An algorithm which helps to reduce the size of files
> Useful to reduce space taken up in secondary storage, or to make sending the file quicker over a network
> Two types: lossy and lossless - 2What is the Difference between Lossy and Lossless Compression?> Lossy - removes unnecessary detail; some data is permanently lost, but enough remains so the file is still useful
> Lossless - none of the original data is lost; an algorithm is used to perfectly restore the original file. This is useful for text or executable files, where all the data is necessary
> Lossy reduces the file size more than lossless - 3What is Run-Length Encoding?> Form of lossless compression that replaces repeating sequences with more efficient representations
> Each repeating string is replaced by a code, which represents the section that repeats, and the amount of times it is to be repeated
> For example, AAABBCCCC becomes 3A2B4C
> This is useful in images, as adjacent pixels are likely to be the same colour - 4What is Dictionary (En)coding?> Useful for text files
> Each word is replaced by a binary number, which represents the word
> A dictionary stores which number represents which word
> Both the dictionary and the string of binary numbers are stored
> Sometimes, pre-existing dictionaries may be used to encode the text - 5What are the Advantages of Dictionary (En)coding?> Takes less bits to store a small binary number than a long word
> No data is lost (i.e., lossless compression)
> Pre-existing dictionaries can be used, meaning the algorithm can quickly encode the data
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- A level Computer Science (Compression, Encryption, & Hashing) Flashcards on Compression, created by Malachy Moran-Tun on 06/12/2022.
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- Malachy Moran-Tun
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