"difference patching" is my word for the method used by patch makers that take only the differences in two files, and apply them to a patch file. RTPatch is an example of a program that does this.

I've been trying to create one myself, but I'm stuck on the logic. The only way I can think of to do it is to compare the bits in both of the files, and if oldfile[x] != newfile[x] then save the offset and value of newfile[x] to the patch file.

I don't think that's the way it should be done, because nearly all the bits will be different, and you'll end up with a larger patch file than it would be with any other patch program.

Maybe I just need a fresh perspective on it, but I can't think of a more efficient way of doing it. Can anyone help?

have you considered using recursion think about it and post back if you need help setting it up

try comparing line by line, not bit by bit.

comparing line by line might be errorneous, but if not its worth a shot. If your trying to patch a file by getting the asic contents of one exe and comparing it with the asci contents of another, that won't work.