What is a CPU?

If you’re just learning about the world of computers and electronics, the terminology used to refer to different parts can be confusing.

CPUs reside in almost all devices you own, whether it’s a smartwatch, a computer, or a thermostat. They are responsible for processing and executing instructions and act as the brains of your devices. Here, we explain how CPUs interact with other parts of your devices and what makes them so integral to the computing process.

The CPU is the core component that defines a computing device, and while it is of critical importance, the CPU can only function alongside other hardware. The silicon chip sits in a special socket located on the main circuit board (motherboard or mainboard) inside the device. It is separate from the memory, which is where information is temporarily stored. It is also separate from the graphics card or graphics chip, which renders the video and 3D graphics that are displayed on your screen. One of the most common advancements in CPU technology is in making those transistors smaller and smaller. That has resulted in the improvement in CPU speeds over the decades, often referred to as 

In the context of modern devices, a desktop or laptop has a dedicated CPU that performs many processing functions for the system. Mobile devices and some tablets instead utilize a system on a chip (SoC) which is a chip that packages the CPU alongside other components. Intel and AMD both offer CPUs with graphics chips and memory stored on them, too, meaning they can do more than just standard CPU functions.
At its core, a CPU takes instructions from a program or application and performs a calculation. This process breaks down into three key stages: fetch, decode and execute. A CPU fetches the instruction from RAM, decodes what the instruction actually is, and then executes the instruction using relevant parts of the CPU.
The executed instruction, or calculation, can involve basic arithmetic, comparing numbers, performing a function, or moving numbers around in memory. Since everything in a computing device is represented by numbers, you can think of the CPU as a calculator that runs incredibly fast. The resulting workload might start up Windows, display a YouTube video, or calculate compound interest in a spreadsheet.