As a side project of mine, I am writing an in depth tutorial about programming an assembler and disassembler. One of the features of the assembler is multiple output formats and I would really like the output to be useable. So what I need is the specification of an executable file format. It doesn’t matter if the format is strictly for NES, C64 or a completely different machine. The important thing is that the format is “real”.

For the Beeb (Acorn systems, including the Electron) the file contains just the bytes that should be loaded (in one contiguous lump) and it's the file system metadata which contains the load address and the execution address. A machine code program might have the load and execution addresses the same, although it need not. A BASIC program would have an execution address pointing into ROM.

For the C64, the first two bytes give the load address (or a suggested load address) - I don't know what the C64 does about execution. Possibly it jumps to the first byte. See
http://fileformats.archiveteam.org/wiki ... executable

Oh, and welcome!

I think you have to know where there is a free block of memory and its memory location on each system.
You also have to know how big that block is on each system.

You need a memory map.
There are books like "Mapping the Commodore 64".
The other issue would be using the Kernal or specific hardware which would be different on each system. I've heard people having problems and their answer was "Use the Kernal" or you are not using the Kernal.

http://www.amazon.com/Mapping-Commodore ... mmodore+64

Also, please take a look at André Fachat's O65 relocatable binary format for another approach. Although André designed O65 with his projects in mind it should be adaptable to other 65xx systems.


It is up to whatever loads the file to jump to the start address. There wasn't anything in the C-64's kernel that was an analog of UNIX's exec... system calls. However, upon completion of the load, locations $AC and $AD (LSB/MSB) hold the load address (also true for the C-128). So a JMP ($AC) instruction should start execution of the program, assuming the load address actually points to executable instructions.

_________________
x86?  We ain't got no x86.  We don't NEED no stinking x86!

http://www.commodore.ca/manuals/pdfs/co ... ry_map.pdf

This is a Commodore 64 and Vic 20 memory map.

Thank you for the information, I will check it out in a few days when I'm finished moving in to my new apartment.

(Thanks for the info about $AC, BDD)