Why and how to use FIFOs for communication between unrelated processes: mkfifo, open flags, blocking behavior and O_NONBLOCK.

How unnamed pipes work, how pipe() and fork() are combined, and a parent-to-child communication example in C.

How fork() duplicates a process, what it returns, how multiple calls multiply processes, and how wait() avoids zombies.

What a process is, how Linux creates processes with fork() and exec(), and how processes communicate.