A decompiler is a computer program that performs the reverse operation to that of a compiler. That is, it translates program code at a relatively low level of abstraction (usually designed to be computer readable rather than human readable) into a form having a higher level of abstraction (usually designed to be human readable). 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. A decompiler takes as input an executable file, and attempts to create a high level, compilable, possibly even maintainable source file that does the same thing. It is therefore the opposite of a compiler, which takes a source file and makes an executable. However, a general decompiler does not attempt to reverse every action of the compiler, rather it transforms the input program repeatedly until the result is high level source code.