This utility patches ".COM" programs so that they will automatically
perform a checksum of themselves when they load.

Use: COMCHK <oldfile> <newfile>

EG:  COMCHK TEST.COM TEST1.COM

The above line will create a TEST1.COM which behaves exactly the same as
TEST.COM, except that it checksums itself befor running the original
program, and aborts with a 'Corrupt image' message if it thinks it has
been altered.

At present, the program only works with ".COM" files < 64K in size.
Source is provided... Feel free to enhance it as you see fit.

The program was written in and can be compiled with MICRO-C version
2.1 (or greater). It should be fairly easy to port to other compilers
or earlier versions of MICRO-C, by modifying the low-level I/O function
calls: "open, close, read, write, lrewind".

To compile with MICRO-C, use:

            cc comchk -flop         /* Produce CAN.OBJ */
            masm/ml ecan;           /* Produce ECAN.OBJ */
            lc comchk ecomchk       /* Link to produce CAN.COM */

This program MUST be compiled in the TINY model (.COM file)... It
references some of its CODE as DATA in order to copy the embedded
function into the patched output file, and therefore must have
overlaid code and data segments.

Enjoy,

Dave Dunfield