Return value of main() tells how the program exited.
If the return value is zero(EXIT_SUCCESS, define in "stdlib.h") it means that the execution was successful while any non zero value will represent that something went bad in the execution.
The default return type of main() is an "int" so its recommend to avoid the use of or better don't use it.
you can use or <main()> as the default return type is int.
printf("Here to check\n");
return 0; // to validate change the return value to different ..
compile the program.
./a.out //execute your program.
echo $? //execute this after executing the above it will show the exit value of "a.out"