Re: Mystery DOS 3.3 mod.

[Rubywand <rubywand@swbell.net>]

Linards Ticmanis writes ...
> 
> I found the following program under the name of "COPYA.ST" on a 1 Jan
> 1983 DOS 3.3 system disk image from the net:
> 
> 10 POKE 47397,24 (i.e. B925- 18 CLC)
> 20 POKE 47398,96 (i.e. B926- 60 RTS)
> 30 PRINT  CHR$ (4)"RUN COPYA"
> 
> Is that on the original 1983 DOS 3.3 Disk? And, dear DOS hackers,
> what's its purpose?
> 
 ....

     It does a patch to the DOS 3.3 Read Sector routine to ignore Data
checksum errors and skip checks of Data epilogue bytes.

     The purpose is to bypass some kinds of copy protection. When it works as
intended, COPYA will be able to read the contents of the original diskette
and write the contents to a normal DOS 3.3 diskette. Other modifications (to
the copy) may be necessary to have a working deprotected copy.

     There are a number of similar patches which might be made to DOS 3.3
before running COPYA. A good reference is the "Super COPYA 1.1" article by
Scott M. Simon in Computist #66. Computist #67 has a couple more good COPYA
articles.

     Most likely, COPYA.ST is intended to be a program which gets changed
depending upon the patch you want in place. (For COPYA with no patches to DOS
3.3, you just RUN COPYA directly.)



Rubywand