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Annotation of researchv9/cmd/compress/README, revision 1.1

1.1     ! root        1: Compress version 4.0 improvements:
        !             2:        o compress() speedup (10-50%) by changing division hash to xor
        !             3:        o decompress() speedup (5-10%)
        !             4:        o Memory requirements reduced (3-30%)
        !             5:        o Stack requirements reduced to less than 4kb
        !             6:        o Removed 'Big+Fast' compress code (FBITS) because of compress speedup
        !             7:        o Portability mods for Z8000 and PC/XT (but not zeus 3.2)
        !             8:        o Default to 'quiet' mode
        !             9:        o Unification of 'force' flags
        !            10:        o Manual page overhaul
        !            11:        o Portability enhancement for M_XENIX
        !            12:        o Removed text on #else and #endif
        !            13:        o Added "-V" switch to print version and options
        !            14:        o Added #defines for SIGNED_COMPARE_SLOW
        !            15:        o Added Makefile and "usermem" program
        !            16:        o Removed all floating point computations
        !            17:        o New programs:
        !            18:                compressdir - compress all files on a directory
        !            19:                uncompressdir - uncompress all files on a directory
        !            20:                zcmp - cmp compressed files
        !            21:                zdiff - diff compressed files
        !            22:          The following are with thanks to philabs!per:
        !            23:                btoa - convert binary to ascii for mailing
        !            24:                atob - convert ascii to binary with checksum
        !            25:                tarmail - tar, compress, btoa, and mail files
        !            26:                untarmail - restore "tarmail" files
        !            27: 
        !            28:                WARNING: These last few programs are not compatible 
        !            29:                with the original ones from the net.  The encoding
        !            30:                has changed.  See btoa.c for more info.
        !            31: 
        !            32: The "usermem" script attempts to determine the maximum process size.  Some
        !            33: editing of the script may be necessary (see the comments).  If you can't get
        !            34: it to work at all, just create file "USERMEM" containing the maximum process
        !            35: size in decimal.
        !            36: 
        !            37: The following preprocessor symbols control the compilation of "compress.c":
        !            38: 
        !            39:        o USERMEM               Maximum process memory on the system
        !            40:        o SACREDMEM             Amount to reserve for other proceses
        !            41:        o SIGNED_COMPARE_SLOW   Unsigned compare instructions are faster
        !            42:        o NO_UCHAR              Don't use "unsigned char" types
        !            43:        o BITS                  Overrules default set by USERMEM-SACREDMEM
        !            44:        o vax                   Generate inline assembler
        !            45:        o interdata             Defines SIGNED_COMPARE_SLOW
        !            46:        o M_XENIX               Makes arrays < 65536 bytes each
        !            47:        o pdp11                 BITS=12, NO_UCHAR
        !            48:        o z8000                 BITS=12
        !            49:        o pcxt                  BITS=12
        !            50:        o BSD4_2                Allow long filenames ( > 14 characters) &
        !            51:                                Call setlinebuf(stderr)
        !            52: 
        !            53: The difference "usermem-sacredmem" determines the maximum BITS that can be
        !            54: specified with the "-b" flag.
        !            55: 
        !            56: memory: at least               BITS
        !            57: ------  -- -----                ----
        !            58:      433,484                    16
        !            59:      229,600                    15
        !            60:      127,536                    14
        !            61:       73,464                    13
        !            62:            0                    12
        !            63: 
        !            64: The default is BITS=16.
        !            65: 
        !            66: The maximum bits can be overrulled by specifying "-DBITS=bits" at
        !            67: compilation time.
        !            68: 
        !            69: WARNING: files compressed on a large machine with more bits than allowed by 
        !            70: a version of compress on a smaller machine cannot be decompressed!  Use the
        !            71: "-b12" flag to generate a file on a large machine that can be uncompressed 
        !            72: on a 16-bit machine.
        !            73: 
        !            74: The output of compress 4.0 is fully compatible with that of compress 3.0.
        !            75: In other words, the output of compress 4.0 may be fed into uncompress 3.0 or
        !            76: the output of compress 3.0 may be fed into uncompress 4.0.
        !            77: 
        !            78: The output of compress 4.0 not compatable with that of
        !            79: compress 2.0.  However, compress 4.0 still accepts the output of
        !            80: compress 2.0.  To generate output that is compatable with compress
        !            81: 2.0, use the undocumented "-C" flag.
        !            82: 
        !            83: Check the Makefile, then "make".

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