The EDIT, FORT, and RLOAD files in this folder are from a Motorola Exorciser.
Calls are made by these programs into the EXBUG monitor primarily for console
and related I/O. There are also some EXBUG variables that are accessed by
these programs. The xxxxPAT.ASM files contain patches to these programs to
to modify these EXBUG references to equivalent functions that have been added
towards the end of the Altair 680 EDOS Resident PROM instead.

To apply the patches, append the xxxxPAT.S19 file to the end of the original
S19 file. Finally, append the letter "S" followed by ESC ($1B) at the end
of the resulting file. This S-ESC sequence marks end of file for the load
routine in the EDOS Resident PROM.

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The FORTRAN library (FORLB.BIN) also includes code that jumps into EXBUG for
I/O. To patch the library (a binary file), I used a hex file editor and 
searched for $7E $F0 to find the jumps to the EXBUG I/O routines at $F0xx.
These were patched to $7E $EB to jump to the equivalent routines in the
Altair 680 EDOS Resident PROM.

The FORTRAN library contains a checksum on each data segment, so when the 
patches are made, the checksum must be updated. The format of a data segment
is:

  "D", length, data[1..length-1], checksum

The checksum is the two's complement of the 8 bit sum of the length byte and
the data bytes. When the checksum is added in as well, the result is zero.

-----------------------------

The ASM and BASIC files are from an Astral 2000 computer. These files had to
be used because an Exorcisor EDOS disk could not be found with the assembler
and BASIC on it. The Astral computer uses a different Resident PROM address
and monitor (i.e., not EXBUG) than the Exorcisor, so the patches required are
different than for the other three files.