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Interesting that, when you compare the MBR and COM versions side-by-side in a hex editor, the only changes (apart from the required few bytes at the end of the MBR version) are in what I assume are memory addresses: a 7D byte in the MBR version ends up being 02 in the COM version. One higher than 7C and 01 in the respective starting addresses.

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You can also easily see this in the (really nice) code, where the only difference is the starting address set at https://github.com/nanochess/Pillman/blob/master/pillman.asm... and the MBR magic bytes in the very bottom.

If you now wonder what the difference between a .com and a .exe file is:

A .com file has a single page which is loaded in that specific location, with all addresses in the code assuming absolute addresses. The .exe (MZ file) allows DOS to put the program anywhere into memory and the rewrite address references (or rather segments) according the relocation table from the program header. With MZ files DOS also sets up space for the stack and sets registers accordingly.

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