38378380
Description
Flashcards by Malachy Moran-Tun, updated more than 1 year ago
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Created by Malachy Moran-Tun
over 2 years ago
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| Question | Answer |
| What 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 |
| What 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 |
| What 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 |
| What 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 |
| What 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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