I want to program a simple assembly language compiler for the experience, but I don't know what compilers write to the .exe files they create. I'm pretty sure it writes 8 digit binary numbers, but I don't know which numbers do what. Any help would be appreciated, thanks.
.exe file mostly contains your program translated into machine language. To get some understanding of what machine language is, you'll have to look into http://en.wikipedia.org/wiki/Assembly_language
But isn't that what compilers do? They compile the source files into object files, then link them into an executable. Aren't executable files lists of binary commands?
I assume Computergeek was thinking about something else (whatever that could be)..
You can surely write a program yourself, using a hex editor. Note that exe contains things other than executable code. .com files are the most simple executable format. They only contain the code. If you want to play around with that, get yourself an assembler, such as http://flatassembler.net/ , and a hex editor.
Oh, I think I know what Computergeek01 was talking about. You can't write a program in 1's and 0's because they are characters and take up one byte, not one bit.
Just to add on, back in the old days, the way to make your scores whatever super high is to use hex editor to open up some binary files and go to some file byte offset and amend the value inside. At least it works in Koei games back in the 80's :P