Putting the "You" in CPU

A technical explainer of how your computer runs programs, from start to finish.

by @kognise and @hackclub


## From the beginning... I've done [a lot of things with computers](https://github.com/kognise), but I've always had a gap in my knowledge: what exactly happens when you run a program on your computer? I thought about this gap — I had most of the requisite low-level knowledge, but I was struggling to piece everything together. Are programs really executing directly on the CPU, or is something else going on? I've used syscalls, but how do they *work*? What are they, really? How do multiple programs run at the same time? A scrawled digital drawing. Someone with long hair is confused as they peer down at a computer ingesting binary. Suddenly, they have an idea! They start researching on a desktop computer with bad posture. I cracked and started figuring as much out as possible. There aren't many comprehensive systems resources if you aren't going to college, so I had to sift through tons of different sources of varying quality and sometimes conflicting information. A couple weeks of research and almost 40 pages of notes later, I think I have a much better idea of how computers work from startup to program execution. I would've killed for one solid article explaining what I learned, so I'm writing the article that I wished I had. And you know what they say... you only truly understand something if you can explain it to someone else. > In a hurry? Feel like you know this stuff already? > > [Read chapter 3](https://cpu.land/how-to-run-a-program) and I guarantee you will learn something new. Unless you're like, Linus Torvalds himself.

Continue to Chapter 1: The "Basics" »
(cpu.land)