decompiler

A decompiler is a computer program that takes as input an executable file, and attempts to create a high level, compilable source file that does the same thing. It is therefore the opposite of a compiler, which takes a source file and makes an executable. Decompilers usually do not perfectly reconstruct the original source code, and can vary widely in the intelligibility of their outputs. Nonetheless, decompilers remain an important tool in software reverse engineering.