When a file is too big, it can be compressed, meaning it can be transformed into a binary file of smaller size1 which contains the same information.
To get the original file back, it must be uncompressed.
uncompress are two original UNIX commands for compression and uncompression, respectively.
The compressed file name ends with a
cat f1 cp f1 f2 ls -l compress f1 ls -l uncompress f1.Z ls -l cmp f1 f2
the reduction of the file size is not guaranteed ↩