🚀 go-pugleaf

fprince@cwis.unomaha.edu (Frank E. Prince) writes:

>Could anyone tell me the difference between .com and .exe files. The
>most I've come up with is that a com file is an "executable memory image"
>but that definition was somewhat out of context, and I don't really
>understand it. I've done some assembly language programming with MASM so
>I do understand instruction sets, stacks, registers etc. Any information
>regarding this is much appreciated.
>			Thanks,
>				Frank

I've posted this since it may be of general interest to others as well.

As far as I understand, a .com file is a direct memory dump (ie no code
relocation can take place) whereas an .exe file contains offsets and indirection
allowing it to be run from (more or less) any location in memory.

Thus, a .com file can be loaded and executed slightly faster than an.exe file
since the processor only has to load the code to a set area (usually the base
of user memory) and jump straight to it.

The only problem with .com files is that there is no separation between the
code segments.  Thus the stack and data segments share the same memory area.
Thus some compilers may throw out the code.

Using Borland Turbo C++, I find that the tiny memory model will suffice,
so compile your code with that and as long as the executable file is less than
64k in length then quit to dos and type :

			exe2bin <filename>.exe <filename>.com

and this will transform your .exe file into a .com file (so now we all know what
this little DOS utility is for :-) ).


So, hope this helps?

Cheers,  Mark...



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