An interactive explainer

Your computer isn't doing many things at once. It's faking it, brilliantly.

A music player, a browser and a download, all running 'at the same time'. On a single core, none of them are. One core runs exactly one instruction stream at a time. It just rotates between tasks faster than your senses can follow. That trick is concurrency, and it is not the same as parallelism. Watch one core juggle three jobs, see what a context switch really costs, then take the scheduler's own dial and change who gets the core.

CPU scheduling · Context switching · Concurrency vs parallelism

Systems · Beginner · 9 min · The multitasking illusion — an interactive explainer on ViLearn, with a simulation and a knowledge check. All explainers.