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What is compression?
to make a file smaller in size
Why is compression used?
files take up less storage space (so more files can be stored)
files can be transferred quicker (because they are smaller)
files can be read from or written to quicker
less bandwidth to transmit
less time to transmit/upload/download
would otherwise exceed email storage
What is lossy compression?
some data (which cannot be seen or heard by humans) is removed by an algorithm from a file to reduce its size
further lossy compression will remove data that humans can see or hear, negatively affecting the quality
data is completely lost once removed - can never get back original file
What is lossy compression commonly used for?
images, audio and video, for example to send over the internet
What is lossless compression?
reduces the size of a file by using Run-length encoding (RLE) which looks at data in a file for consecutive runs of the same data. These are stored as one item of data instead of many
no data is removed permenantly and file can be returned to its original form when decompressed
no quality is lost but doesn’t reduce file size as much
What is lossless compression commonly used for?
files that would be useless if data was removed permanently - text files
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