(CPU) means,Central processing unit,it is a principal part of any digital computer system, generally composed of the main memory, control unit, and arithmetic-logic unit. It constitutes the physical heart of the entire computer system; to it is linked various peripheral equipment, including input/output devices and auxilliary storage units. In modern computers, the CPU is contained on an integrated circuit chip called a microprocessor.

circuit board

The control unit of the central processing unit regulates and integrates the operations of the computer. It selects and retrieves instructions from the main memory in proper sequence and interprets them so as to activate the other functional elements of the system at the appropriate moment to perform their respective operations. All input data are transferred via the main memory to the arithmetic logic unit for processing, which involves the four basic arithmetic functions (i.e., addition, subtraction, multiplication, and division) and certain logic operations such as the comparing of data and the selection of the desired problem-solving procedure or a viable alternative based on predetermined decision criteria.

CPU Components

A typical CPU has a number of components. The first is the arithmetic logic unit (ALU), which performs simple arithmetic and logical operations. Second is the control unit (CU), which manages the various components of the computer. It reads and interprets instructions from memory and transforms them into a series of signals to activate other parts of the computer. The control unit calls upon the arithmetic logic unit to perform the necessary calculations.

a CPU contains an arithmetic logic unit, a control unit, and a cache

Third is the cache, which serves as high-speed memory where instructions can be copied to and retrieved. Early CPUs consisted of many separate components, but since the 1970s, they have been constructed as a single integrated unit called a microprocessor. As such, a CPU is a specific type of microprocessor. The individual components of a CPU have become so integrated that you can’t even recognize them from the outside. This CPU is about two inches by two inches in size.

what is a CPU can be answered by looking to examples from Intel

CPUs are located on the motherboard. Motherboards have a socket for this, which is specific for a certain type of processor. A CPU gets very hot and therefore needs its own cooling system in the form of a heat sink and/or fan.

CPU with heatsink and fan to cool down hot computer processors

The ALU is where the calculations occur, but how do these calculations actually get carried out? To a computer, the world consists of zeros and ones. Inside a processor, we can store zeros and ones using transistors. These are microscopic switches that control the flow of electricity depending on whether the switch is on or off. So the transistor contains binary information: a one if a current passes through and a zero if a current does not pass through.

Transistors are located on a very thin slice of silicon. A single silicon chip can contain thousands of transistors. A single CPU contains a large number of chips. Combined, these only cover about a square inch or so. In a modern CPU, however, that square inch can hold several hundred million transistors – the very latest high-end CPUs have over one billion! Calculations are performed by signals turning on or off different combinations of transistors. And more transistors means more calculations. You may be interested to know that the material, silicon, used in chips is what gave the Silicon Valley region of California its name.

The Main Functions of the CPU

The CPU processes instructions it receives in the process of decoding data. In processing this data, the CPU performs four basic steps:

  1. Fetch: Each instruction is stored in memory and has its own address. The processor takes this address number from the program counter, which is responsible for tracking which instructions the CPU should execute next.
  2. Decode: All programs to be executed are translated to into Assembly instructions. Assembly code must be decoded into binary instructions, which are understandable to your CPU. This step is called decoding.
  3. Execute: While executing instructions the CPU can do one of three things: Do calculations with its ALU, move data from one memory location to another, or jump to a different address.
  4. Store: The CPU must give feedback after executing an instruction, and the output data is written to the memory.

The number of operations a CPU can perform depends upon its speed, which is measured in Hertz. One hertz is the speed during which one operation is performed in one second. Typically a computer’s speed is measured in gigahertz. 1 GHz is the speed it takes the CPU to perform one million simple tasks. A “simple task” includes the smallest steps a processor can perform.

Usually, the processor understands and performs assembly instructions that last four cycles. The faster your CPU, the more instructions it can perform in one second, but do not let this number fool you. The speed of the CPU is not the only metric that influences your computer’s performance. There are many other factors, such as CPU architecture, cache size, and bus speed that must be evaluated to get independent results. Do not simply chase the highest speed when buying a processor. Evaluate all of the factors.


The CPU is the brain of a computer, containing all the circuitry needed to process input, store data, and output results. The CPU is constantly following instructions of computer programs that tell it which data to process and how to process it. Without a CPU, we could not run programs on a computer.

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Author: refuge_2020

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