You have a long list of machine language instructions. You know (roughly) what the output of the compiler looks like when translating from source code to machi

You have a long list of machine language instructions. You know (roughly) what the output of the compiler looks like when translating from source code to machine language for various constructs like functions, if statements, etc. (a compiler course helps here). Some reverse engineering tools provide partial automation for that to assist in this deciphering. After that, it's just a lot of painstaking, grinding work.