COMPACT(1)              GENIX Programmer's Manual              COMPACT(1)



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

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

      DESCRIPTION
           Compact compresses the named files using an adaptive  Huffman  code.
           If  no file names are given, then 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  com-
           pact.  If no file names are given, then the standard input is uncom-
           pacted 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

      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.



      Printed 11/16/83                                                        1

      COMPACT(1)              GENIX Programmer's Manual              COMPACT(1)



      AUTHOR
           Colin L. Mc Master

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      Printed 11/16/83                                                        2