Data compression is used behind the scenes in computer systems quite often, computer files and other kinds of data can be compressed to a smaller size for easy storage or transportation. Later, they are decompressed and used in their original form. One basic idea is to find parts of the data that are identical to each other and use some kind of trick to describe that more efficiently. Run-length encoding (RLE) encodes a run of repetitions with the length of that run. RLE is a simple compression algorithm (an algorithm which takes a block of data and reduces its size, producing a block that contains the same information in less space). It works by replacing repetitive sequences of identical data items with short tokens that represent entire sequences. Applying RLE to a string involves finding sequences in the string where the same character repeats. Replace each such sequence by a token consisting of: the number of characters in the sequence the repeating character.