#include<stdio.h>
#include<signal.h>
void abc();
main()
{
printf("Press ctrl+c for teminating\n");
signal(SIGINT,abc);
signal(SIGINT,abc);
signal(SIGINT,abc);
for(;;
}
void abc()
{
printf(" U have pressed ctrl+c\n");
}
iam unable understand the program
how this ctrl+c works with SIGINT and DEL works with SIGINT in linux to terminate the program.

Your little program will trap the SIGINT signal and so you can't quit by pressing CTRL-C. If you don't handle the signal then bash will and will terminate the program.

Compile and run the program. Press ctrl-c. It will print "U have pressed ctrl+c" instead of terminating.
Next open another terminal (xterm or konsole) and enter in "killall -SIGINT ctc". It will print the same message. You used killall to send a signal to the process named "ctc". You can quit the program by entering "killall -SIGQUIT ctc" in the second terminal.

Normally you would use the signal to do something else, like closing files and releasing memory. Maybe you have child processes that you will send SIGQUIT to.

Be sure to read the "man 2 signals" manpage as well as the "info bash" section 3.7.6 Signals.