Freeze/Melt

Freeze is a file compression utility used from the command line in Unix-style operating systems. Melt is the corresponding decompressor. It is considered obsolete now in favor of gzip.

A two-pass compression is done with a Lempel-Zev algorithm on the first pass and a dynamic Huffman algorithm on the second. The characteristics of the Huffman table used are added to the file. File attributes, ownership, etc., are preserved, and a .F extension is added. A two-byte magic number is prepended to the file (\037\236 octal for versions 1.x, and \037\237 for later versions).