void exit(int status)

This function may be called to forcibly terminate the program at any point. The parameter status is simply a number which is, in some sense, made available to the "external" environment of the program. In any case, if you are using exit() to terminate your program, you should normally just give it one of two pre-defined exit values which have been given symbolic names in stdlib.h: use exit(EXIT_SUCCESS) if the program is terminating "normally" and exit(EXIT_FAILURE) if it is terminating because of some unexpected or intolerable exception or error being encountered.