VMSLZ.HLP

The files VMSLZ1.ARC, VMSLZ2.ARC, and VMSLZ3.ARC contain an adaptation of the
Unix 'compress' program to VAX/VMS by Martin Minow of DEC
(minow%rex.dec@decwrl.arpa), as submitted to the DECUS library.  The files are
in DOS-ARC format, which can be picked apart by a VMS program call TARC.EXE
(which we don't have), or can be easily decomposed with a text editor.  The
Unix compress program was originally written by Spencer Thomas, et al., to
implement the Lempel-Ziv (LZ) file compression algorithm (as described by Terry
Welch in IEEE Computer V17 #6, whose initial is sometimes appended to the
acronym to make it LZW), which replaces common strings of bytes with compact
codes in a single pass over a file in a deterministic manner.  The VMS version
of this facility adds knowledge of FILES-11/RMS file structure, and compresses
record-oriented files together with their attributes, restoring them to their
original form upon decompression.

The files are:

VMSLZ1.ARC - contains a readme file, plus 3 pieces of the compression program.
VMSLZ2.ARC - decompression program, in 3 pieces
VMSLZ3.ARC - header files, common functions, makefile, formatted documentation

The archive format is strictly textual, with each file beginning with a line
of the form 

-h- filename     date-time     origin

The LZ programs are written in C, and can be compiled with VAX-11 C, DECUS C,
or under Unix.  The VMS-specific features are switch-selectable.

Note that the ARC format described above is not the same as the MS-DOS ARC
format, in which multiple files are archived into a single file, each
compressed by the most appropriate algorithm (run-length, Huffman, or LZW).

[End of VMSLZ.HLP]
