


      COMPACT(1)                  (bsd 4.2)                  COMPACT(1)



      NAME
           compact, uncompact, ccat - compress and uncompress files,
           and cat them

      SYNTAX
           compact [ name ... ]
           uncompact [ name ...  ]
           ccat [ file ... ]

      DESCRIPTION
           Compact compresses the named files using an adaptive Huffman
           code.  If no file names are given, the standard input is
           compacted to the standard output.  Compact operates as an
           on-line algorithm.  Each time a byte is read, it is encoded
           immediately according to the current prefix code.  This code
           is an optimal Huffman code for the set of frequencies seen
           so far.  It is unnecessary to prepend a decoding tree to the
           compressed file since the encoder and the decoder start in
           the same state and stay synchronized.  Furthermore, compact
           and uncompact can operate as filters.  In particular,

                ... | compact | uncompact | ...

           operates as a (very slow) no-op.

           When an argument file is given, it is compacted and the
           resulting file is placed in file.C; file is unlinked.  The
           first two bytes of the compacted file code the fact that the
           file is compacted.  This code is used to prohibit
           recompaction.

           The amount of compression to be expected depends on the type
           of file being compressed.  Typical values of compression
           are:  Text (38%), Pascal Source (43%), C Source (36%) and
           Binary (19%).  These values are the percentages of file
           bytes reduced.

           Uncompact restores the original file from a file compressed
           by compact. If no file names are given, the standard input
           is uncompacted to the standard output.

           Ccat cats the original file from a file compressed by
           compact, without uncompressing the file.

      RESTRICTION
           The last segment of the filename must contain fewer than
           thirteen characters to allow space for the appended '.C'.

      FILES
           *.C       compacted file created by compact, removed by
           uncompact




      Page 1                                          (73 A2 02MT REV1)






      COMPACT(1)                  (bsd 4.2)                  COMPACT(1)



      SEE ALSO
           Gallager, Robert G., `Variations on a Theme of Huffman',
           I.E.E.E.  Transactions on Information Theory, vol. IT-24,
           no. 6, November 1978, pp. 668 - 674.

           pack(1)

















































      Page 2                                          (73 A2 02MT REV1)



