The internal circuit of the computer can complete all kinds of arithmetic operations at high speed and accurately. Nowadays, the operation speed of computer system has reached trillions of times per second, and the microcomputer can reach more than one hundred million times per second, so that a large number of complex scientific calculation problems can be solved. For example, the calculation of satellite orbit, the calculation of large dams, and the calculation of 24-hour weather take years or even decades, while in modern society, it takes only a few minutes to complete with computers.

Computer, commonly known as computer, is a modern electronic computer used for high-speed calculation, which can perform numerical calculation as well as logical calculation, and also has the function of storage and memory. It is a modern intelligent electronic device that can run according to the program and process massive data automatically and at high speed.

It is composed of hardware system and software system, and a computer without any software installed is called bare metal. It can be divided into five categories: supercomputers, industrial control computers, network computers, personal computers and embedded computers. The more advanced computers include biological computers, photonic computers and quantum computers.

In 1944, Huo Po wrote a program for Harvard Mark 1, the world's first computer. Howard aiken built Mark 1 at Harvard University. It takes about 6 seconds to calculate a multiplication.

John von neumann, inventor of computer. Computer is one of the most advanced scientific and technological inventions in the 20th century, which has had an extremely important impact on human production and social activities. Its application field has expanded from the initial military scientific research application to all fields of society, and has formed a huge computer industry, which has promoted the technological progress around the world. Computers have spread all over ordinary schools, enterprises and institutions, entered the homes of ordinary people, and become an indispensable tool in the information society.

The application of computers is becoming more and more common in China. After the reform and opening up, the number of computer users in China has been rising and the application level has been improved, especially in the fields of Internet, communication and multimedia. From 1996 to 2009, the number of computer users increased from 6.3 million to 67.1 million, and the number of networked computers increased from 29,000 to 59.4 million. The number of Internet users has reached 316 million, and the wireless Internet has 670 million mobile users, of which 117 million are mobile Internet users, ranking first in the world.

Due to the development of integration technology, semiconductor chips are more integrated, each chip can accommodate tens of thousands or even millions of transistors, and the arithmetic unit and controller can be concentrated on one chip, resulting in the emergence of microprocessors, which can be assembled into microcomputers with large-scale and ultra-large-scale integrated circuits, that is, microcomputers or PCs. Microcomputer is small, cheap and easy to use, but its function and operation speed have reached or even surpassed that of large computers in the past. On the other hand, all kinds of logic chips made of large-scale and ultra-large-scale integrated circuits have been made into giant computers, which are not very large in size, but can operate at a speed of 100 million or even billions of times. In 1983, China successfully developed the Galaxy I supercomputer with 100 million operations per second, and in 1993, it successfully developed the Galaxy II universal parallel supercomputer with 1 billion operations per second. This period also produced a new generation of programming languages, database management systems and network software.

With the changes of physical elements and devices, not only the host computer has undergone upgrading, but also its external devices are constantly changing. For example, the external memory developed from the initial cathode ray display tube to the magnetic core and drum, and then to the universal magnetic disk, and now there is a CD-ROM with smaller volume, larger capacity and faster speed.

A computer is composed of a hardware system and a software system.

The hardware units of traditional computer systems can generally be divided into input unit, output unit, arithmetic logic unit, control unit and memory unit, among which arithmetic logic unit and control unit are collectively called central processing unit (CPU).

hardware system

Power Supply 

Power supply is an indispensable power supply equipment in computer. Its function is to convert 220V alternating current into 5V, 12V and 3.3V direct current used in computer. Its performance directly affects the stability of other equipment, and then affects the stability of the whole machine. The laptop provide an effective power supply for that laptop unde the condition that the laptop is provided with a lithium battery.

mainboard

Motherboard is a platform where all parts of the computer work. It connects all parts of the computer closely, and all parts transmit data through the motherboard. In other words, the important "transportation hub" in the computer is on the motherboard, and its stability affects the stability of the whole machine.

CPU

CPU is the central processing unit, which is the computing core and control core of a computer. Its function is mainly to interpret computer instructions and process data in computer software. CPU is composed of arithmetic unit, controller, register, cache and bus for data, control and status. As the core of the whole system, CPU is also the highest execution unit of the whole system, so CPU has become the core component that determines the performance of the computer, and many users use it as a standard to judge the grade of the computer.

internal storage

Memory, also called internal memory or random access memory (RAM), is divided into DDR, SDRAM, ECC and REG. (However, SDRAM has been eliminated by DDR because of its low capacity, slow storage speed and poor stability.) Memory is an electronic storage device, which is composed of circuit boards and chips. It is characterized by small size, high speed, power storage and no power emptying, that is, the computer can store data in the memory when it is turned on, and will automatically empty it after it is turned off. Memory includes DDR, DDR2, DDR3 and DDR4, with a capacity of 1-256GB.

hard disc

Hard disk belongs to external memory, and mechanical hard disk is made of metal magnetic disk or glass magnetic disk, and magnetic disk has memory function, so the data stored on magnetic disk will not be lost whether it is turned on or off. Hard disk has a large capacity, reaching TB level, with dimensions of 3.5, 2.5, 1.8, 1.0 inches, etc. The interfaces are IDE, SATA, SCSI, etc. SATA is the most common. Mobile hard disk is a storage product that takes hard disk as storage medium and emphasizes portability. Most mobile hard disks in the market are based on standard hard disks, and only a few are based on micro hard disks (1.8-inch hard disks, etc.), but the price factor determines whether mainstream mobile hard disks are based on standard notebook hard disks. Because the hard disk is used as the storage medium, the data reading and writing mode of the mobile hard disk is the same as that of the standard IDE hard disk. Mobile hard disks mostly use USB, IEEE1394 and other interfaces with faster transmission speed, which can transmit data with the system at a higher speed. Solid-state hard disk is a hard disk made of solid-state electronic memory chip array, which consists of a control unit and a memory unit (FLASH chip). Solid-state hard disk is completely consistent with ordinary hard disk in product shape and size, but solid-state hard disk is faster than mechanical hard disk.

sound card

The sound card is an indispensable hardware device for a multimedia computer. Its function is to convert the sound digital signal in the computer into an analog signal and send it to the sound box to make sound.

display card

When working, the graphics card cooperates with the display to output graphics and characters. Its function is to convert and drive the display information needed by the computer system, and provide line scanning signals to the display to control the correct display of the display. It is an important component connecting the display with the motherboard of the personal computer and one of the important devices of "man-machine dialogue".

network card

The network card is a network component working in the data link layer, and it is the interface connecting computers and transmission media in the local area network. It can not only realize the physical connection and electrical signal matching with the transmission media in the local area network, but also involve the functions of frame sending and receiving, frame encapsulation and unpacking, media access control, data encoding and decoding, and data caching. The function of the network card is to act as a bridge between the computer and the network cable. It is one of the important devices used to establish a local area network and connect to the Internet.

In the integrated motherboard, the sound card, graphics card and network card are often partially or completely integrated on the motherboard.

modem

The English name is "Modem", commonly known as "cat", that is, modems, which are built-in and external, wired and wireless. Modem is one of the essential devices when surfing the Internet through telephone lines. Its function is to convert the digital signals processed on the computer into analog signals transmitted by telephone lines. With the popularization of ADSL broadband network, the built-in modem gradually withdrew from the market.