Some time before the event occurs, you must have "registered" your event handling function for a particular signal value.

        void myhandler(int signum)
        {
           printf("Ouch, you interrupted me!\n");
        }
        int main()
        {
          if ( signal(SIGINT, myhandler) == SIG_ERR ) {
             printf("signal error\n");
             exit(1);
          }
          pause();
          
          exit(0);
        }