

   -----------------------------
    CRIDERS COMPRESSION SYSTEM: 
   -----------------------------


- 1984 by G. C. Crider


CCSEXP:
*******

This is the machine language
expansion program used to expand
a compressed file back to it's
original condition.
     1. Use the load binary file
feature of DOS or your favorite
menu to load the program and begin
execution.  DOS must be resident.
     2. Insert the source and
destination diskette(s) in the
drive(s).
     3. Enter the file specs
(including Dn:) of your input
(compressed) file and output
(normal) file as requested by the
program.  Use of wild cards could
produce incorrect results or loss
of data.
Do not use the input file as
the output file.  This will result
in an ERROR 0.
     CCS will be able to determine
the correct density if the drive
has been properly configured prior
to execution of CCSCOMP.  The new
ATARI DOS 3 "double density" will
probably not work.
     4. Expansion begins
immediately and is complete when
the words "END OF JOB" appear on
the screen.

ERROR PROCESSING

The CCS programs display standard
error codes used by DOS and the ATARI
operating system.  There are three
additional codes used by CCS
described below:

     ERROR 0 - Issued by CCSCOMP
and CCSEXP to indicate that the
output file is the same file as
specified for input.  CCSALL uses
this code to indicate that the
output disk is the same as the
input disk.

     ERROR 1 - Issued by CCSEXP to
indicate that the input file is not
a compressed file and erroneous
result might occur if the expansion
were allowed to continue.  It is
also issued by CCSCOMP and CCSALL
to indicate that the file you are 
attempting to compress is already 
in compressed format.

     ERROR 2 - Issued by CCSCOMP
and to indicate that the
characters $FEEF and $CBCF both
appear in the input file (very 
rare!).  Since one or the other of
these strings will be used by the
compression program to indicate the
presence of a compression word 
(explained later), the expansion 
program or menu would not expand 
the file properly.  Compression is 
terminated.  This file cannot be 
compressed.  Very few files will 
cause this error. 

    The presence of any error
condition except ERROR 0 will cause
the output file to be deleted when
CCSCOMP or CCSEXP is being
executed.  

HOW DOES IT WORK?

CCS replaces contiguous
occurances of five or more
identical bytes with one or more
four byte compression words.  The
construct of the compression word
is as follows:

Bytes 0-1 = $FEEF  compression flag.
This indicates that the next 2 bytes
are compression data. If, during the 
course of compresion, The characters 
$FEEF are detected in the input file,
an alternate flag of $CBCF is used. 
If both are detected in the input 
file, ERROR 2 will result.

Byte 2 = Number of repetitions of the
character less one.

Byte 3 = The char. to be repeated.

If there are more than 256
repetitions of a character,
additional compression words are
written until the entire stream is
represented.

AFTERWORD

If you would like the latest
versions of all of the above
mentioned utilities, send me a
disk, self-addressed mailer and
postage along with $5 to cover
copying costs and I will return the
diskette with the programs and
documentation files.  If you want
to send me some software you think
I might like, forget the $5 charge!
It is O.K. if I already have it.
It is the thought that counts.

If you encounter difficulties
with this or any of my programs, do
not hesitate to call or write.  I
don't guarantee a fix, but maybe I
can offer a little sympathy.

     Gary C. Crider
     1105 Burgess Ct.
     Arlington, TX 76015
     (817) 467-1114
      (817) 467-1114


