Generally speaking, "the first electronic digital computer recognized in the world" is considered by most people as "ENIAC" which came out in 1946. It is mainly used to calculate the trajectory. It is manufactured by Moore Institute of Electrical Engineering, University of Pennsylvania, USA, but it is huge, covering an area of 170 square meters, weighing about 30 tons, and consumes nearly 140 kilowatts of electricity. Obviously, such computers are expensive and inconvenient to use. This statement is widely used in basic computer textbooks. In fact, according to the ruling of the US Supreme Court 1973, the earliest electronic digital computers should be john atanasoff, an associate professor in the Department of Physics of He Hua University, and Clifford Berry, his graduate assistant (181963). The reason for this misunderstanding is that a man named Moakley in the "ENIAC" research group copied john atanasoff's research results at 194 1 and applied for a patent at 1946. For various reasons, this error was not reversed until 1973. (See "john atanasoff" in Baidu Encyclopedia for details. I hope everyone will remember ABC and john atanasoff, and I hope this mistake can be corrected in future textbooks). Later, in order to commend and commemorate john atanasoff's great contribution in the computer field, former US President George W. Bush awarded john atanasoff the "National Science and Technology Award", the highest American science and technology award.
1956, the transistor electronic computer was born, which is the second generation electronic computer. Only a few larger cabinets can be installed, and the operation speed is greatly improved. The third generation of integrated circuit computers appeared in 1959.
The original computer was invented by john von neumann (at that time, the computing power of the computer was equivalent to the current calculator), which was as big as three warehouses, and then gradually developed.
This is the latest stage of computer development since 1970s. By 1976, "Cray" made of LSI and VLSI made the computer enter the fourth generation. With the invention of VLSI, electronic computers are constantly upgrading to miniaturization, miniaturization, low power consumption, intelligence and systematization.
In the 1990s, computers developed in the direction of "intelligence", creating computers similar to human brains, which can do thinking, learning, memory and network communication.
In the 265,438+0th century, computers have become more notebook-oriented, miniaturized and specialized, with an operation speed of over 65,438,000 billion times per second. It is not only easy to operate and cheap, but also can replace part of people's mental work and even expand people's intelligence in some aspects. Therefore, today's microcomputers are vividly called computers.
The first personal computer in the world was introduced by IBM in 1980. IBM introduced a personal computer based on Intel x86 hardware architecture and Microsoft MS-DOS operating system, and formulated the PC/AT specification. After that, the development of the microprocessor introduced by Intel and the operating system introduced by Microsoft is almost equivalent to the development history of personal computers. Wintel architecture completely replaced IBM's dominant position in the field of personal computers.
There are many types of computers according to their types, working modes, components, working principles and application conditions.
As far as data representation is concerned, computers can be divided into three categories: digital computers, analog computers and hybrid computers.
Digital computers are divided into mechanical computers and electromechanical computers, current electronic computers, optical computers, quantum computers, biological computers, neural computers and so on.
According to its scale or system function, electronic computers can be divided into giant, large, medium, small, microcomputer and single-chip microcomputer.
Taken together, the classification of computers is like this:
(1) classified by performance indicators
① Supercomputer: high speed and large capacity.
(2) Mainframe: High speed, applied in military technology and scientific research.
③ minicomputer: simple structure, low cost and outstanding cost performance.
④ Microcomputer: small size, light weight and low price.
(2) Classification by purpose
① Special machine: with strong pertinence, specific service and special design.
② General computer: scientific calculation, data processing and process control to solve various problems.
(3) Classification according to principles
① Digital machine: high speed, high precision, automation and multifunction.
(2) Simulator: Analog quantity is used as operation quantity, which is fast and has poor accuracy.
③ Mixer: It is in the development stage, combining the strengths of the former two and avoiding their weaknesses.
No matter what kind of computer, it is composed of hardware and software, which are inseparable. People call a computer without any software installed as bare metal.
Hardware appliance
Electronic circuits and physical devices used in computer systems are tangible entities, such as central processing unit (CPU), memory, external devices (input and output devices, I/O devices) and buses.
1 memory. The main function is to store programs and data. Program is the basis of computer operation, and data is the object of computer operation. The memory consists of memory bank, address decoder, read-write control circuit, address bus and data bus. The memory that can directly and randomly access instructions and data by the central processing unit is called the main memory, and the large-capacity memory such as magnetic disk, magnetic tape and optical disk is called the external memory (or auxiliary memory). The storage system of a computer consists of main memory, external memory and corresponding software.
② The main function of the central processing unit is to execute the operations specified by the program one by one according to the programs in the memory. The main components of the central processing unit are: data register, instruction register, instruction decoder, arithmetic logic unit, operation controller, program counter (instruction address counter), address register, etc.
③ External equipment is the bridge between users and machines. The task of the input device is to convert various forms of information that users require the computer to process, such as data, characters, characters, graphics and programs, into a code form acceptable to the computer and store it in the computer. The task of the output device is to output the processing results of the computer in the form required by users (such as screen display, text printing, graphics and charts, language sounds, etc.). ). I/O interface is a buffer device between external devices and CPU, which is responsible for electrical performance matching and information format conversion.
software
A collection of programs that can make a computer hardware system work smoothly and effectively. Programs are always stored and represented by some physical media, such as disks, tapes, program paper, punched cards, etc. But software does not refer to these physical media, but refers to the invisible and intangible programs themselves. Reliable computer hardware is like a person's strong physique, and effective software is like a person's intelligent thinking.
Computer software system can be divided into system software and application software. System software is responsible for the management, scheduling, monitoring and service of the whole computer system resources. Application software refers to various applications developed by users in different fields for their own needs. The computer software system includes:
① Operating system: the core of system software, which is responsible for the management, control and monitoring of various soft and hard resources in the computer system.
② Database management system: responsible for the management and sharing of all files, materials and data in the computer system.
(3) Compilation system: responsible for compiling the source program written by users in high-level language into machine language that the machine can understand and execute.
④ Network system: responsible for organizing and managing the network resources of computer systems, so that multiple independent computers can share and communicate with each other.
⑤ Standard library: a collection of programs written in a standard format, including calculation programs for solving elementary functions, linear equations, ordinary differential equations, numerical integrals, etc.
⑥ Service program: also called utility program. Various programs provided to enhance the service function of the computer system, including the functions of installation, connection, editing, error detection, error correction and diagnosis of user programs. In order to make the computer fast and accurate, remember more and more firmly, for decades, it has been improving the processing speed of the central processing unit in a single machine.