How to change the logic/code for Windows?

There is a program on windows 8.

In the program it is necessary to change/fix/add a few functions.

there is a search function ( with fields to fill) in the program and need to add to the search form a new field which is searched, and to add some more features

There is an assumption that it is written in C++.

What are the possible solutions for fixing the code and save changes in the program?

thank you!
July 2nd 19 at 17:35
2 answers
July 2nd 19 at 17:37
If the source code can not get the simple options there.

There is the option of disassembly, build your dll, but this operation is so complex that judging from your question it makes no sense to undertake.
If the program is simple, easier to order as a freelancer and write from scratch, obtaining and software and source code for the future.
July 2nd 19 at 17:39
If no source - it's much easier to write from scratch.

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