Come again ???? are you talking about reverse engineering programs ? Or what ??
Theres basicaly
NO way you can be sure to find the exact orriginal code.
Altho there are some
1;
2 programs out there which will help.
In order to prevent people from reverse engineering
1;
2 a program, programmers use
scramblers to obfuscate the code, so it isn't easy to fugure out.
Usualy reverse engineering is a matter of having a great debugger and knowing how to use it. Plus beeing well known in bin/hex/oct calculations.