What will happen if i return other than 0?

Answer 1

"The return value for main should indicate how the program exited. Normal exit is generally represented by a 0 return value from main. Abnormal termination is usually signalled by a non-zero return but there is no standard for how non-zero codes are interpreted.
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It's also worth noting that in C++, int main() can be left without a return value at which point it defaults to returning 0."

Source: http://stackoverflow.com/a/204483

Answer 2

Nothing, once return 0 is read by the processor the program terminates.