return value from main

check the following program
/*a.c*/
int main()
{
return 0;
}
returns 0 to the shell and echo $? gives 0
/*b.c*/
void main()
{
}
echo $? in shell gives some different values for each execution what does it represents????

 

It represents the fact that you haven't returned a value. The values are meaningless; you should not try to use them if the program doesn't return a value. But you should always return zero from main unless you have a good reason for returning some other specific value; zero indicates success, and for any script calling your program and relying on the return codes to check for errors a garbage return will cause undefined behaviour within the script.

If you know for certain that your program will NEVER EVER be called by a script that checks return values, and that returning garbage will definitely have no negative effects, then go ahead and return garbage. Otherwise at least return 0; it's not a difficult line to add. Or return EXIT_SUCCESS; if you prefer.

 

Always define main as returning an int, then return one. It's that simple.

 

The current C++ standard mandates that the main() function return int. However you don't have to ACTUALLY return a value. If the control flows out of main without reaching a return statement, it is equivalent to return 0;
On the other hand,
void main() is ill-formed