Compression
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What is lossless compression
No data is lost during compression
What is lossy compression
Some data is lost
When should lossy compression be used
On data that human perception wouldn’t notice
What is run length encoding
Removes unnecessary data by replacing repeated values with a count and then the value itself
What don’t dictionary based compression algorithms encode
Single symbols as variable length strings
What does dictionary based compression algorithms encode
Variable length strings of symbols as single tokens
When does compression occur in dictionary based compression
If the tokens are smaller than the phases they replace
What does dictionary based compression use to retrieve information
Indexes in databases to retrieve information from large amounts of storage
What is the format of dictionary based coding
X/Y X = page in dictionary Y = number of word on page
How many bytes per word in dictionary based compression
2.5
How many bytes per letter in ASCII
1