What is a CPU?

A CPU, or central processing unit, is the brains of the electronic system it controls. The most familiar CPUs –also called microprocessors -- are found in desktop and laptop personal computers, yet millions of CPUs are also used in what we call "embedded applications". CPUs are programmable. In other words they can be programmed to execute a range of instructions, to perform arithmetic and logical operations on data, and control input/output of data. This makes CPU's very versatile. They may – as we see in the familiar example of PCs – run lots of different programs. They may also be programmed to perform the specific functions required in a range of different types of electronic equipment, ranging from consumer electronics for the home to mobile devices to enterprise IT equipment for the data center.

Embedded CPUs may be combined with other circuitry to create a "System-on-a-Chip" (SoC) solution. For example the chips used to power mobile phones, network switching equipment and hard disk drive controllers all incorporate CPUs that are embedded in SoC solutions.

A CPU is typically the fastest running and most advanced component in any SoC. Because it is programmable, the CPU can be called upon to perform a wide range of tasks. Often these include tasks that were not considered—or did not exist—when the product was originally designed. For example, the mobile phone that you use today probably has many more functions than the one you used two years ago. These upgrades are possible, in large part, because the CPU can be programmed to perform additional tasks. This versatility is a key benefit of CPUs.

However, the more functions a CPU has to perform, the more powerful the "brain circuit" needs to be. Thus we have seen rapid advances in CPU technology driven by demands for ever more capability in electronic systems. Hard disk drives need to store more data and access it more rapidly. Mobile devices that can fit in your pocket need to provide the functionality of a PC. And in the home we need central hubs or gateways to handle all of the various data flows from TVs and PCs.

You can also think of the CPU as the manager of an electronic system. The CPU is in charge of how the system works. It sends some tasks to ancillary devices, but handles most of the brain work itself. Then it gathers the results and makes a decision. That "decision" might be the solution to a complex mathematical problem, or it could be a digitally enhanced picture of your dog! It may be the optimal route to enable rapid retrieval of data from a hard disk drive, or it might be the ability of your mobile phone to recognize your voice commands.