Operating Systems

The earlier posts, how computers run programs and inside a running process, started with a program already running. This one goes further back, to the moment you press the power button, and follows the chain that has to happen before any of that machinery exists. What firmware is Firmware is software. The difference from ordinary software is where it lives and what it does. Regular software, your browser or the OS, sits on your hard disk or SSD....

The first post followed the chain from disk to CPU. This one goes deeper into what actually happens once a program is running: how its memory is laid out, how the OS keeps track of it, and how many programs share the machine at once. From passive to active A program sitting on the hard disk is a passive thing. Just saved instructions, doing nothing. The moment you run it, it becomes an active process living in RAM....

Every time you open an app, a chain of hardware kicks into motion behind the scenes. This post follows that chain from the disk all the way to the CPU, one idea building on the last. 1. Why RAM is faster than a hard disk RAM is electronic. Data is fetched by sending electrical signals, almost instantly. A hard disk drive (HDD) is mechanical. It has spinning platters and a moving arm that must physically travel to the right spot before it can read....