File compression reduces the size of a ire so it uses less space than normal.
Explicit utilities must be called by the user, usually from the DOS prompt, to compress or decompress a file or group of files. Background utilities operate automatically, decompressing files as they are used and recompressing them after they are no longer needed. While background utilities are more convenient for the user, the system suffers a slight decrease in performance whenever a file is accessed from the disk. No system performance loss is experienced with explicit utilities, but the user must take the time to decompress files before using them. Historically, this method of compression, often called archiving, has been used to save large quantities of files to diskettes for long term storage.