Catching SIGALRM Signal: Self-driven using alarm function

What makes SIGALRM signal something special?  It is generally used with alarm function.
It is similar to raise function, except for 2 things

1. SIGALRM is the only signal generated out of alarm function
2. The signal is not raised immediately.  It is raised after some delay, that is specified by user.

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#include <stdio.h> #include <signal.h> #include <unistd.h> void alarm_catch(int signum) { printf("\tCaught the signal %d\n",signum); } void main() { //Registering SIGALRM signal signal(SIGALRM,alarm_catch); //Raise SIGALRM signal to same process after 3 seconds alarm(3); //Timer loop for 5 seconds: Each print message denotes one second passed for(int i=0;i<5;i++) { printf("TIME\n"); fflush(stdout); sleep(1); } }

Steps will be like this

1. Registering the signal 
2. Raising alarm.(To raise SIGALRM after 3 seconds)
3. Timer Loop for 5 seconds

After alarm function is executed, next line of code will be executed without any delay. In the background, after 3 seconds SIGALRM would have been raised.
When we execute the program

root@kali:~# ./a.out
TIME
TIME
TIME
 Caught the signal 14
TIME
TIME

 We got 'Caught the signal 14'(alarm_catch function is executed) after 3 TIME messages (3 seconds, argument of alarm).