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    CRIDERS COMPRESSION SYSTEM: 

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- 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