Like a human brain is the center of all human activities and functions. Similarly, CPU is the brain of the computer which implements all the programs, control the flow of operations and displays the output with the help of input-output (I/O) devices. Before moving further, let’s quickly discover the full form of CPU.
The full form of the abbreviation CPU is Central Processing Unit.
This tutorial will briefly cover the meaning, history, types, parts of CPU, operations of CPU and other detailed information related CPU or Central processing unit.
What is meant by CPU?
“CPU or Central processing unit, also known as the central processor, main processor (sometimes only processor), is the electronic circuitry part of any digital computer system that executes instructions to regulate the computer program. The CPU carries out basic arithmetical and logical operators, linked various peripheral equipment, controls input/output (I/O) devices, and auxiliary storage units.”
CPU is defined as the brain of a computer system. Every computer has a separate CPU socket segment where the Central processing unit or CPU is installed inside the motherboard to execute systems I/O operations. It performs all the necessary logical and arithmetic activities and directs the computer's commands and functions. The term CPU is typically used to indicate a processor that contains the ALU and CU i.e.,
CPU = ALU + CU
CPU stands for Central processing unit
ALU stands for Arithmetical Logical Unit
CU stands for control unit
History of CPU
The first electronic computers were invented generations back with a fixed purpose. Therefore, there was a set of electronic circuits that allowed the user to do one particular thing. But modern computers are very different and can serve various purposes at one time. This all happened because of CPU evolution. The brief history of CPU is as follows:
- In 1823, Baron Jons Jackob introduced the first fundamental component of processors.
- Later in the year 1903, Nikola Tesla patented the logic circuits which today we refer as electronic gates or switches.
- Transistors were developed in 1947 at Bell Laboratories by three scientists named John Barden, Walter Brattain and William Shockley.
- Integrated circuit was invented in 1958 by Robert Noyce and Jack Kilby.
- Intel developed the world’s first microprocessor named Intel 4004 on 15 November 1971.
- AMD introduced the family of AM386 microprocessor in March 1991.
- Intel further released the fastest Pentium processor in March 1993, which consists of 60 MHz processor with approximately 3.1 million transistors.
- Further Intel developers discovered the Celeron 553 MHz bus processor on 4 January 2000, Intel.
- In April 2006, Intel further introduced the high speed Core 2 Duo processor E6320.
- Intel discovered the world’s first Core i7 processors in November 2008.
- Intel launched the first Core i5 Mobile processors (i5-430M and i5-520E) in January 2010.
Types of CPU
Typically, there are three types of Central Processing Unit:
- Transistor type CPU
- LSIT or Large Scale Integration type CPU
- SSIT or Small Scale Integration type CPU
Parts of CPU
1. ALU or Arithmetical Logical Unit
ALU is the vital unit of the CPU. It performs and manages numerical and logical calculations, like difference, sum, division, multiplication, etc. Arithmetical Logical Unit (ALU) contains two subsections that are given below:
- Arithmetic Section: The arithmetic section executes arithmetic operations like sum, subtraction, multiplication, and division. The various computer calculations are performed by making constant use of the ALU operations.
- Logic Section: The logic section executes various logic operations such as comparing, selecting, pairing and merging, etc.
2. Control Unit (CU)
CU is the chief component of the CPU. It assigns the task to the computer, and it synchronizes all the system activities that happen. The various functions of the control unit (CU) are as following:
- Control Unit manages the transfer of information and instructions between the other two units of a computer system.
- Control Unit regulates and controls all the units of the system.
- CU (Control Unit) fetches the data (in the form of instructions) from the memory unit, decodes it, and leads the computer's operation.
Control Unit is responsible for managing the communication between Input/ Output (I/O) devices and looks after the transfer of information or results from storage.
3. Register or Memory Unit
A register is a special kind of tool for storing memory. The memory stores the already processed data or the data in a queue, waiting for the processor to process it.
This unit stores instructions, information, and outputs. It provides data to other computer units when required. The memory unit has several different names, such as main memory or the internal storage or primary memory, or RAM (Random Access Memory). The size of the memory Unit influences the speed, power, and capability of the computer system. It is further divided into primary memory and secondary memory. The various functions of the memory unit are as following:
- Memory Unit is responsible for storing all the information and the instructions needed for data processing.
- Memory Unit holds all the intermediate processing outputs.
- Memory Unit holds the final processing output results of processing before these outcomes are passed to any output device to display.
- All I/O operations are carried through the main memory unit.
Operation of CPU
CPU is the fundamental building block of a computer. We have computers that run programs that are store in memory. Computers have two components. 1. CPU and 2. Memory
The CPU fetches an instruction on what it needs to do next from memory. It then executes that instruction and goes back and brings the next instruction from memory, and then it performs that instruction and so on. Now, of course, today, there are lots of other things that happen. The computers have graphics cards, PCI bus, USB, hard disk, but at the very most superficial level, the memory and the CPU work together to feed the CPU with a set of instructions.
So what do these instructions tell the CPU to do?
The CPU has a state, and that state is measured in two different ways. One is by a set of registers, and other is by some status flags. The registers contain a slot where you can put bits of information and manipulate those bits of information. There's a part of the CPU state, where its program counter is, wherein memory is fetching the next instruction. So every time you execute the instruction, the program counter is incremented. It goes forward to the next location in memory. Like this, the entire process repeats, following the fetch, decoding, and executing steps in their operation, known as the instruction cycle.