Also known as: CPU, central processing unit, processor
The central processing unit (CPU) is the chip that carries out a program’s instructions — the part of computer hardware most often called the “brain.”1
Overview
A CPU fetches instructions, decodes them, and executes them one after another, very fast. Modern CPUs contain several cores: each core is a self-contained processing unit, so a multi-core CPU can genuinely work on several tasks at the same time. This is what makes concurrency and parallel work practical.
Clock speed, measured in gigahertz (GHz), counts how many cycles a core runs per second. It is a rough guide to speed, not an absolute one — a newer 3 GHz core can outpace an older 4 GHz core because it does more useful work per cycle.
Where it fits
The CPU scales across the whole hardware spectrum. A microcontroller has a single tiny, low-power core; a desktop has a handful; a server may carry dozens. The CPU works hand in hand with RAM, which holds the data and instructions it is actively using.
Sources
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Central processing unit — Wikipedia, on CPU function, cores, and clock speed. ↩