/* Solution 1: */ int main(int argc, char* argv[]) { if( argc == 2 || main( 2, NULL ) ) { printf("Hello "); } else { printf("World\n"); } return 0; } /* Solution 2 (Only for Unix and Linux): */ int main(int argc, char* argv[]) { if( !fork() ) { printf("Hello "); } else { printf("World\n"); } return 0; }