Q What is incompressible data?

A Data that cannot be compressed e.g. most music, video and image file formats.

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The process of compressing data involves running algorithms to identify patterns and then representing the same data using a more compact form e.g. a file might consist of the character sequence 123456789 which might be represented by a compressor as [1-9]. This would reduce the file-size by nearly 50%. Because application (.exe) and library (.dll) files do not tend to take up a lot of space, they are generally not compressed by default. On the other-hand music, photos and video files tend to be compressed by default, they would take up too much space if they were left uncompressed. Within the context of disk storage some controllers automatically compress data before writing it to physical storage. When data is requested it is automatically de-compressed. This results in less blocks written to the underlying disk and therefore increased data throughput for compressible data.