- prototype in signal.h - raises signal to program where 'sig' is: SIGABRT signal abnormal termination SIGILL signal illegal instruction SIGSEGV signal illegal storage access SIGFPE signal floating point error SIGINT signal Ctrl-Break interrupt SIGTERM signal program termination (ignored in MS DOS) SIGUSR1 user signal SIGUSR2 user signal SIGUSR3 user signal - returns 0 on success; nonzero otherwise - see signal()