Compiling, as far as I know, converts human-readable code (C, Fortran, whatever) into machine code. I don't think it's possible to fully reverse. People who reverse engineer applications have to do a lot of guesswork, and know more than just how to write a program, since the tools available can't show them the code as it was originally written, but only some sort of translation from the machine code into something editable. At least this is my understanding.
Even SWF files cannot be completely decompiled to their original state, but the result can give the viewer an idea of how it was built.
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/ >) My 84-year-old non-techy mom uses Debian Linux. It ain't that hard.