Why do we type return 0 at the end of a program

Question

what will happen if I type return 1

Answer 1

The return value of the main function is considered the "Exit Status" of the application to the most of the operating systems and returning 0 value is a success status that tell the OS that program has terminated properly and safely.

Answer 2

0 is a stand in for None. That is, no error occurred. When your program fails it will return 1: Something went wrong. In the past, people would sometimes define special error codes. So the program might return 5 on a certain problem.