Patcher is a program run in MSDOS that lets the user detect and describe the possible differences between two files.
Patcher is especially designed to make comparisons of two different versions of the same file so that you can quickly locate the differences between them, if there are any.
For programmers it`s interesting that on the Patcher author`s website you can find the source code (in C++) of how the program was done. Also, Patcher is totally free. For it to work correctly you need Visual Basic 6.0 or later.