Computer is a highly automated electronic equipment, which can receive and store information, process and process the input information according to the programs stored in it (these programs are the embodiment of human will), and then output the processing results.

Second, the birth of electronic computers.

1, the world's first computer, ENIAC, 1946 was born in the United States in February. It does not have the main principle features of modern computers-stored programs and program control.

2. The world's first computer, EDVAC, designed according to the function of stored programs was designed in the United States in 1946 and developed in 1950.

3.EDSAC is the first computer in the world to realize the function of storing programs. It was designed by Britain at telephone number 1947 and put into operation in May.

Third, the development of computers.

According to electronic logic devices, the development of electronic computers can be divided into four stages:

1, the first generation of computers (from the advent of ENIAC to the early 1950s), in the electron tube era, light screen tubes or mercury delay circuits were used as memory, and punched paper tapes or cards were used as input and output. The software is in the primary stage, there is no system software, and the language is only machine language or assembly language. The application is mainly based on scientific calculation.

2. The second generation computer (from the mid-1950s to the mid-1960s), in the transistor era, used magnetic cores and drums as memory, and produced advanced programming languages and batch processing systems. The application field extends to data processing and transaction processing, and is gradually used in industrial control.

3. The third generation computer (from the mid-1960s to the early 1970s), in the era of small and medium-sized integrated circuits, the main memory began to use semiconductor memory, and the external memory included disks and tapes, an operating system, a standardized programming language and a Basic language for man-machine dialogue. It is not only used in scientific calculation, but also in the fields of enterprise management, automatic control, aided design and aided manufacturing.

4. The fourth generation of computers (from the mid-1970s to the present), in the era of large-scale VLSI, computer applications involve office automation, database management, image recognition, voice recognition, expert system and other fields, and have entered the family.

Fourth, computer classification.

Computers can be divided according to their use, scale or processing objects.

1, by purpose

(1) General-purpose computer: suitable for solving various general problems. This computer has a wide range of applications and strong versatility, and can be adapted to scientific calculation, data processing and process control.

(2) Special machine: used to solve a specific problem, equipped with software and hardware to solve a certain problem, such as in special applications such as automatic control of production process and industrial intelligent instruments.

2, according to the scale.

(1) Supercomputer: used for cutting-edge national defense technology and modern scientific calculation. The operation speed of supercomputers can reach billions of times per second, and the development of supercomputers is an important symbol to measure a country's economic strength and scientific level.

(2) Large/medium-sized computers: high computing speed, capable of executing tens of millions of instructions per second and large storage space. It is usually used for scientific calculation, data processing or as a network server.

(3) Small computers: small in scale, simple in structure and low in requirements for operating environment, and are generally used for data acquisition in industrial automatic control, measuring instruments and medical equipment. As an auxiliary machine of giant computer system, minicomputer also plays an important role.

(4) Microcomputer: The central processing unit (CPU) uses microprocessor chips, which are small in size and light in weight, and are widely used in automatic control, office automation and popular information processing in commerce, service industry and factories.

(5) Workstation: a high-function computer based on personal computing environment and distributed network environment. Workstation is not only a tool for numerical calculation and data processing, but also a working machine supporting artificial intelligence operation. Through network connection, various computers, including workstations, can transmit information to each other, share resources and information, and distribute loads.

(6) Server: a shared device that provides services for multiple users under the network environment, which is generally divided into file servers, print servers, computing servers and communication servers.

3, according to the processing object.

(1) Digital computer: When the computer processes, the input and output values are all numbers.

(2) Analog computer: The data object to be processed is the direct and continuous analog data such as voltage, temperature and speed.

(3) Digital-analog hybrid computer: Input and output can be both digital data and analog data.

Verb (abbreviation for verb) the characteristics of a computer

Computer is a highly automated information processing equipment. The main features are high processing speed, high calculation accuracy, strong memory ability, reliable logical judgment ability, high reliability and strong versatility.

1. Fast processing speed: The computing speed of a computer is measured by MIPS (how many millions of instructions are executed per second).

2. High calculation accuracy: the accuracy of a number mainly depends on the number of bits of the binary code representing this number.

3. Strong memory ability: Memory ability can store a lot of data and computer programs.

4. Reliable logical judgment ability: Reliable logical judgment ability is an important feature of computers and an important reason why computers can realize information processing automation.

5. High reliability and versatility.

Six, computer performance indicators

The main technical performance indexes of computer include main frequency, word length, memory capacity, access cycle, operation speed and so on.

1, main frequency (clock frequency): refers to the number of pulses output by computer CPU in unit time. To a great extent, it determines the running speed of the computer. Unit MHz.

2. Word length: refers to the number of bits of binary data that can be processed by the computing components of a computer at the same time. The word length determines the calculation accuracy of the computer.

3. Memory capacity: refers to the total number of bytes of information that can be stored in memory. Usually, 8 binary bits can be used as a byte.

4. Access cycle: the shortest time required for two consecutive independent "read" or "write" operations of the memory, in nanosecond (ns, 1ns= 10-9s). The time required for a memory to complete a "read" or "write" operation is called the access time (or reading and writing time) of the memory.

5. Operation speed: it is a comprehensive index, and the unit is MIPS (millions of instructions per second). The main frequency and access period, word length and storage capacity also affect the operation speed.

Other indicators: machine compatibility (including data and file compatibility, program compatibility, system compatibility and equipment compatibility), system reliability (MTBF), system maintainability (MTTR), maximum number of external devices allowed by machine configuration, Chinese character processing capability of computer system, database management system and network function, etc. Cost-performance ratio is a comprehensive index to evaluate computer performance.

Seven, the application field of computer

The application scope of computer can be divided into scientific calculation, information processing, process control, computer-aided system, multimedia technology, computer communication and artificial intelligence according to its application characteristics.

1, scientific calculation: refers to the application of computers to complete mathematical problems raised in scientific research and engineering technology (numerical calculation). Generally, computers are required to have high speed, high precision and relatively large storage capacity. Scientific calculation is the earliest application of computer.

2. Information processing: Information processing mainly refers to non-numerical data processing, including data collection, storage, processing, classification, sorting, retrieval and publishing. Information processing includes office automation, enterprise management, information retrieval, newspaper arrangement, etc. It is characterized by a large amount of raw data to be processed, simple arithmetic operation, large amount of logical operation and judgment, and the results need to be stored and output in the form of tables or files. The computer is required to have a large storage capacity, but the speed is not very high. Information processing is the most widely used at present, accounting for about 80% of all applications.

3. Process control: computer is used for process control in the fields of science and technology, military, industry and agriculture. And the computer control system needs special digital-to-analog conversion equipment and analog-to-digital conversion equipment (called D/A conversion and A/D conversion). Because process control is generally real-time control, sometimes the speed of the computer is not high, but it requires high reliability and timely response.

4. Computer-aided system: There are computer-aided instruction (CAI), computer-aided design (CAD), computer-aided manufacturing (CAM), computer-aided testing (CAT), computer integrated manufacturing (CIMS) and other systems.

5. Multimedia technology: a technology that organically combines various media such as numbers, characters, sounds, graphics, images and animations, establishes logical connections among them by using computer, communication and radio and television technologies, and processes them (including input, compression and decompression, storage, display and transmission of these media). ). At present, the application fields of multimedia computer technology are constantly expanding. Besides knowledge learning, e-books, business and family applications, it has also been greatly promoted in telemedicine and video conferencing.

6. Computer communication: It is the product of the combination of computer technology and communication technology. With the development of computer network technology, computers located in different regions are connected through communication lines and equipped with corresponding software to achieve the purpose of resource sharing.

7. Artificial intelligence: a discipline that studies, explains and simulates human intelligence, intelligent behavior and its laws. Its main task is to establish the theory of intelligent information processing, and then design a computing system that can show some intelligent behaviors similar to human beings. The disciplines of artificial intelligence include knowledge engineering, machine learning, pattern recognition, natural language processing, intelligent robots and neural computing.