Return 0 or return 1 - what the difference?

Question

Guys, I do not understand the difference between return 0 and return 1, return 2, and so on.
If I change return 0 to return 1, then 2 + 2 will remain equal to 4.
https://code.sololearn.com/cZ3BMs7gSRBA/?ref=app

Answer 1

It depends on the system you run the program on, some test the return and respond based on it. A return of non-zero on those systems will have an effect.