What is a CPU?

CPU (central processing unit) the central unit in a computer containing the logic circuitry that performs the instructions of a computer's programs. The CPU performs arithmetical, logical operations on data held in the computer memory - the RAM. The RAM is seen as a vector that contains instructions and data provided by the computer programmer.

The CPU relies on an "Operating system" such as Windows or MacOS for input and output of data, interaction with the user or storing information on the disk.

Most of the CPUs made today are produced by Intel or AMD, and all of these use the same "instruction set" - or how the instructions are coded to the CPU. There are controversy about these CPU's first of all in the way that they "see" and address the memory, that is highly inefficient.


CPU stands for the Central Processing Unit of a computer system. The CPU can deal with many millions of calculations per second. Bytes of data travel about the computer on electronic pathways, known as buses.

Data from the CPU travels along these buses to other parts of the computer, telling them what to do. How quickly the CPU can deal with calculations is decided by the number of bytes that it can process at once (its bandwidth), and the number of instructions it can deal with during one second. The "clock speed" is like a metronome that determines the beat, and the instruction type will determine how many "clock cycles" are needed per instruction. Like incrementing a number held in a register to the CPU is much faster than incrementing a variable held in memory.

The instructions are provided by programmers, that has coded in a formal computer language all the instructions. It will need an operating system to load instructions and show results - allow us to use the computer.

You will find CPU in microprocessors used in digital watches, cameras, and cell phones that are just the same as those for "server systems" and "mainframes" for databases and websites. However faster and larger computers may have many CPU that even share the same memory, and is programmed to work together. When CPUs share the same memory, special precautions must be made to avoid interfering with one another. This requires that the cache memory held close to the CPU to improve speed, is either shared (e.g. "dual core") - or needs to be synchronised ("Scalable Coherent Interface") and brings on a new level of complexity.

Or to put it really simply; the CPU is like the human brain, performing all of the calculations required to complete a program.