How to open .cpp .h and others file in C program?

Question

C++ / C#

I have a program that reads a file in a certain way and outputs a message-result.
The whole problem is that I can only open .txt files, but I would really like to open files with code directly, let's say .сpp .h

Answer 1

Um... well, open it. these are all the same text formats, the file extension does not care at all.