Which is the different between
int main(void)
void main()
void main(void)?

int main( void ) doesn't take any arguments, and returns an integer which usually indicates success or failure. Usually you won't care much about what main's return value is, but I suppose you could use it to tell whoever called it whether it had an error or not. void main() and void main(void) are the same. The empty parentheses imply no arguments to main, just as with any other function. The void return value means you don't need to return anything from main, although I think the standard practice is to use an int return value (and some compilers will even force you to use int as the return value).

Stick to int main() or int main(int argc, char** argv) since these are the ISO standards.

Don't forget that if you use

int main()

You must return some value when your main function is done...

int main()
{
return 0;
}

If you use void, however, you are not expected to do that. I strongly encourage you to use int, though

void main()
{
return;
}

well it's worth it to take a look and see what exactly main is returning to.
seeing this it is clear that main should ALWAYS return a value. however it is optional
for main to have argc,argv. if they are not there, void should be. so, you should have either: