A signal can be defined as an asynchronous event that is delivered to a target process. Signals are delivered to the target process either by another process or the OS (the kernel) itself.
At the code level, a signal is merely an integer value; more correctly, it is a bit in a bitmask. It's important to understand that, although the signal may seem like an interrupt, it is not an interrupt. An interrupt is a hardware feature; a signal is purely a software mechanism.
OK, let's try a simple exercise: run a process, putting it in an infinite loop, and then manually send it a signal via the keyboard. Find the code in (ch11/sig1.c):
int main(void){ unsigned long int i=1; while(1) { printf("Looping, iteration #%02ld ...
