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# What is a CPU?

## CPUs or processors

CPU stands for _Central Processing Unit_ or Central Processing Unit. It’s like the brain of a computer. This unit interprets and executes the basic instructions that allow a computer to function. The term CPU is generally used interchangeably with the word processor.

A processor consists of several distinct parts. These include the arithmetic logic unit (referred to as ALU), the control unit and the cache. 

The ALU’s role is to perform mathematical and logical operations. The control unit coordinates the activities of the entire processor. Finally, the cache stores the data and instructions frequently used by the CPU.

The speed of a processor is measured in hertz (Hz), which is a unit of measure of frequency. One Hz is equivalent to one cycle per second. The faster a CPU is able to execute instructions, the higher its frequency will be.

The first processors were created in the early 19th century. They were then known as mechanical calculators, and only mathematicians and scientists were able to use them. 

Today, processors are everywhere. They are found in many electronic devices such as smartphones, tablets and smart TVs. 

These CPUs are both much smaller and millions of times more powerful than 19th century mechanical calculators.