4 lessons
What is a process, really?
The difference between a program sitting on disk and the same program actually running, and everything the OS tracks about it.
Process states and the art of pausing mid-thought
The five-state life of a process, and the surprisingly expensive trick the OS uses to pause one process and resume another.
Process creation, fork, and exec
Where new processes actually come from, and the strange but brilliant two-step trick Unix uses to create and start them.
Threads — many workers sharing one process's kitchen
Why threads exist, how they differ from processes, and the real math behind when multithreading actually speeds things up.