Question

Can someone exlain me what is that “return” at the end of the function and why we have to write at the end of the main function return 0.e.g

int main()
 {
  .....
  return 0;
 }

Answer 1

You don’t have to write return at the end of main in C++; a return value of 0 is implicit. (This is different in C, where you do have to return a value.)

What this does is return a value to the program’s environment, so that it can be known whether the program succeeded (zero) or encountered some error (non-zero). Other programs, including shell scripts/batch files can use this information to make decisions, e.g. they can stop early when an error is encountered in a program they run.