The evolution of computing tools has gone through different stages from simple to complex, from low-level to high-level, for example, from knots in "Notes on Knots" to counting chips, abacus slide rules, and mechanical computers. They have played their respective historical roles in different historical periods, and also inspired the development of modern electronic computers.
In 1889, American scientist Herman Hollery developed an electric tabulating machine based on electricity
to store computing data.
In 1930, American scientist Vannevar Bush created the world's first analog electronic computer.
On February 14, 1946, the world's first electronic computer "ENIAC Electronic Numerical And Calculator" (ENIAC Electronic Numerical And Calculator) customized by the US military came out at the University of Pennsylvania. ENIAC (Chinese name: Eniac) was developed by the Auberdine Weapons Test Site in the United States to meet the needs of calculating ballistics. This calculator uses 17,840 electron tubes, with a size of 80 feet × 8 feet and a weight of 28t ( ton), the power consumption is 170kW, the operation speed is 5,000 addition operations per second, and the cost is about 487,000 US dollars. The advent of ENIAC has epoch-making significance, indicating the arrival of the era of electronic computers. In the next 60 years, computer technology has developed at an astonishing rate, and the performance-price ratio of no technology can increase by 6 orders of magnitude within 30 years.
Generation 1: Tube Digital Machines (1946-1958) electronic tube digital computer electronic tube digital computer In terms of hardware, the logic components use vacuum tubes, the main memory uses mercury delay lines, cathode ray oscilloscope electrostatic memory, magnetic drums, and magnetic cores; the external memory uses magnetic tape. The software uses machine language and assembly language. The application areas are mainly military and scientific computing. The disadvantages are large size, high power consumption and poor reliability. It is slow (generally thousands to tens of thousands of times per second) and expensive, but it lays the foundation for future computer development.
Generation 2: Transistor Digital Machines (1958-1964) The application fields of operating systems, high-level languages and their compiled programs in software are mainly scientific computing and transaction processing, and they have begun to enter the field of industrial control. It is characterized by reduced size, reduced energy consumption, improved reliability, increased computing speed (usually 100,000 times per second, but up to 3 million times per second), and its performance has been greatly improved compared to the first generation of computers.
The third generation: integrated circuit digital machine (1964-1970) In terms of hardware, the logic elements use medium and small scale integrated circuits (MSI, SSI), and the main memory still uses magnetic cores. In terms of software, time-sharing operating systems and structured and large-scale programming methods appeared. It is characterized by faster speed (usually from millions to tens of millions of times per second), and the reliability has been significantly improved, the price has been further reduced, and the products have become generalized, serialized and standardized. The field of application began to enter the field of word processing and graphic image processing.
4th generation: LSI computers (1970-present) On the hardware side, large-scale and very large-scale integrated circuits (LSI and VLSI) are used for logic elements. In terms of software, database management systems, network management systems and object-oriented languages have emerged. In 1971, the world's first microprocessor was born in Silicon Valley, USA, ushering in a new era of microcomputers. The application field gradually moves from scientific computing, transaction management, and process control to family. Due to the development of integration technology, the integration level of semiconductor chips is higher, each chip can accommodate tens of thousands or even millions of transistors, and operators and controllers can be concentrated on one chip, thus the emergence of microprocessors, And it can be assembled into a microcomputer with a microprocessor and a large-scale, ultra-large-scale integrated circuit, which is what we often call a microcomputer or a PC. Microcomputers are small in size, cheap and easy to use, but their functions and computing speed have reached or even exceeded those of the past large computers. On the other hand, various logic chips manufactured by using large-scale and ultra-large-scale integrated circuits have been made into supercomputers that are not very large in size, but can operate at a speed of 100 million or even billions of times. Following the successful development of the Galaxy I supercomputer with 100 million operations per second in 1983, my country successfully developed the Galaxy II general-purpose parallel supercomputer with one billion operations per second in 1993. This period also produced a new generation of programming languages, database management systems and network software. With the change of physical elements and devices, not only the mainframe of the computer has undergone upgrading, but also its external equipment is constantly changing. For example, external memory has developed from the original cathode ray display tube to the magnetic core and the magnetic drum, and later developed into a general-purpose magnetic disk. ).
The hardware units of a computer system can generally be divided into an input unit, an output unit, an arithmetic logic unit, a control unit, and a memory unit. The arithmetic logic unit and the control unit are collectively called the Central Processing Unit (CPU).
The power supply is an indispensable power supply device in the computer. Its function is to convert the 220V alternating current into the 5V, 12V, and 3.3V direct current used in the computer. The quality of its performance directly affects the stability of other equipment. The stability of the whole machine. Laptops provide effective power for laptops with their own lithium batteries.
The motherboard is a platform for the various components in the computer to work, it connects the various components of the computer closely together, and each component transmits data through the motherboard. In other words, the important "transportation hubs" in the computer are all on the motherboard, and the stability of its work affects the stability of the whole machine.
The 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. The CPU consists of arithmetic units, controllers, registers, caches, and a bus that implements data, control, and status connections between them. As the core of the entire system, the CPU is also the highest execution unit of the entire system. Therefore, the CPU has become the core component that determines the performance of the computer. Many users use it as a standard to judge the grade of the computer.
Memory, also known as internal memory or random access memory (RAM), is divided into DDR, SDRAM, ECC, REG, (but SDRAM has been eliminated by DDR due to its low capacity, slow storage speed, and poor stability) memory is an electronic storage device. It consists of a circuit board and a chip. It is characterized by small size, high speed, and can be stored with electricity, and can be emptied without electricity, that is, the computer can store data in the memory when it is turned on, and all data in it will be automatically emptied when it is turned off. There are three types of memory: DDR, DDR2, DDR3, and DDR4, with a capacity of 1-256GB. 
The sound card is an indispensable hardware device for forming a multimedia computer. Its function is to convert the sound digital signal in the computer into an analog signal and send it to the speaker to emit sound after a playback command is issued.
When working, the graphics card cooperates with the monitor to output graphics and text. Its function is to convert and drive the display information required by the computer system, and to provide line scan signals to the monitor to control the correct display of the monitor. It is an important component for connecting the monitor and the mainboard of the personal computer. , is one of the important devices for "man-machine dialogue".
The network card is a network component that works at the data link layer. It is the interface connecting the computer and the transmission medium in the local area network. It can not only realize the physical connection and electrical signal matching with the transmission medium of the local area network, but also involve the sending and receiving of frames, frame encapsulation and decapsulation, media access control, data encoding and decoding, and data caching functions. The role 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, part or all of the sound card, graphics card, and network card are often integrated on the motherboard.
The English name is "Flash disk", and a flash disk is also commonly referred to as a USB flash drive, a USB flash drive, or a flash drive. It is a universal serial bus USB interface that does not require a physical drive. Storage medium (Flash Memory). A flash disk generally includes a flash memory (Flash Memory), a control chip and a casing. The flash disk has the advantages of multiple erasing, high speed and anti-magnetic, shock-proof and moisture-proof. The flash disk adopts the popular USB interface, the size is only the size of the thumb, the weight is about 20 grams, no driver, no external power supply, plug and play, file exchange between different computers, storage capacity ranging from 1 ~ 128GB, to meet different requirements demand.
The English name is "Modem", commonly known as "cat", that is, modem, there are built-in and external, wired and wireless. A modem is one of the essential devices when surfing the Internet over a phone line. Its function is to convert the digital signal processed on the computer into an analog signal transmitted by the telephone line. With the popularization of ADSL broadband network, the built-in modem has gradually withdrawn from the market.
The English name is "Optical Disk driver", a machine that computers use to read and write CD-ROM content, and is also a relatively common component in desktop and notebook computers. With the more and more extensive application of multimedia, CD-ROM has become a standard configuration in many computer accessories. Optical drives can be divided into CD-ROM drives, DVD drives (DVD-ROM), combo (COMBO) and DVD recorders (DVD-RAM) and so on. The ability and speed of reading and writing are also increasing, 4 × 16 × 32 × 40 × 48 ×.
The English name is "monitor". The display is large or small, thin or thick, and has various varieties. Its function is to display the results processed by the computer. It is an output device and one of the indispensable parts of a computer. It is divided into three categories: CRT, LCD, and LED. The interfaces include VGA, DVI, VGA DVI, HDMI DP, type-C, S-video, and AV interfaces.
The English name is "Keyboard", which is divided into wired and wireless. The keyboard is the main artificial input device, usually with 104 or 105 keys, which is used to input characters, numbers, etc. to the computer, as well as computer control.
The English name is "Mouse". When people move the mouse, there will be an arrow pointer on the computer screen to move with it, and it can accurately point to the desired position and quickly locate it on the screen. It is indispensable for people to use the computer. one of the components. There are two types of keyboard and mouse interfaces: PS/2 and USB. The hardware mouse is divided into two types: photoelectric and mechanical (mechanical has been eliminated by photoelectric).
The English name is "Loud speaker", which is connected to a power amplifier through an audio cable, and then amplifies the sound through a transistor and outputs it to the speaker, so that the speaker emits the sound of the computer. General computer speakers can be divided into 2, 2.1, 3.1, 4, 4.1, 5.1, 7.1, and the sound quality is also different.
The English name is "Printer", through which the files in the computer can be printed on paper, and it is one of the important output devices. In the field of printers, three main products, including dot matrix printers, inkjet printers and laser printers, have been formed, each of which exerts its advantages to meet the different needs of users from all walks of life.
Devices such as cameras, scanners, digital cameras, digital video cameras, and TV cards are used to process video signals.
The hard disk is an external memory, and the mechanical hard disk is made of metal magnetic disk or glass magnetic disk, and the magnetic disk has a memory function, so the data stored on the magnetic disk will not be lost whether it is turned on or off. The hard disk has a large capacity, reaching the TB level, and the size is 3.5, 2.5, 1.8, 1.0 inches, etc., and the interfaces include IDE, SATA, SCSI, etc., SATA is the most common. Mobile hard disks are storage products that use hard disks as storage media and emphasize portability. The vast majority of mobile hard drives on the market are based on standard hard drives, and only a few are based on micro hard drives (1.8-inch hard drives, etc.), but the price factor determines whether mainstream mobile hard drives are based on standard notebook hard drives. Base. Because the hard disk is used as the storage medium, the data read and write mode of the mobile hard disk is the same as that of the standard IDE hard disk. Most mobile hard disks use interfaces with faster transmission speeds such as USB and IEEE1394, which can transmit data to the system at a higher speed. A solid-state hard disk is a hard disk made of a solid-state electronic storage chip array, which consists of a control unit and a storage unit (FLASH chip). Solid-state drives are completely the same as ordinary hard drives in product shape and size, but solid-state drives are faster than mechanical hard drives.
A memory card is a memory that uses Flash Memory technology to store electronic information. It is generally used in digital cameras, handheld computers, MP3, MP4 and other small digital products as storage media, so it looks small and looks like a card, so it is called for flash memory cards. According to different manufacturers and different applications, flash memory cards include Smart Media (SM card), Compact Flash (CF card), Multi Media Card (MMC card), Secure Digital (SD card), Memory Stick (memory stick), TF Although these flash memory cards have different appearances and specifications, the technical principles are the same. Since the flash memory card itself cannot be directly recognized by the computer, the card reader is a communication bridge between the two. Card Reader (Card Reader) can use many kinds of memory cards, such as Compact Flash or Smart Media or Microdrive memory card, etc., as the information access device of the memory card. The card reader uses USB1.1/USB2.0 transmission interface and supports hot-plugging. Just like a normal USB device, just plug it into your computer's USB port, then insert a memory card and you're ready to go. According to the speed, there are USB1.1, USB2.0 and USB3.0. According to the purpose, there are single card reader and multi-in-one card reader.