how do signal work in c code example

Example 1: signal handlers in c

kill -l for all the signals

use signal function to register signal handlers
man signal

Example 2: c signals

#define SIGHUP  1   /* Hangup the process */ 
#define SIGINT  2   /* Interrupt the process */ 
#define SIGQUIT 3   /* Quit the process */ 
#define SIGILL  4   /* Illegal instruction. */ 
#define SIGTRAP 5   /* Trace trap. */ 
#define SIGABRT 6   /* Abort. */