Introduction
Electronic digital computer is an electronic computer that performs calculation and storage inside the machine in the form of numerical values. The representation of numbers is often binary. It is composed of arithmetic unit, controller, memory, input and output equipment, input and output channels, etc. According to the main performance indicators, it is divided into minicomputers and microcomputers.
Electronic digital computers are known for their fast calculation speed, high calculation accuracy, large amount of information storage, high degree of automation, and ability to make logical judgments. It can be used not only for numerical calculation and data processing, but also for automatic control and information processing. Electronic digital computers have been widely used in such departments as atomic energy, nuclear weapons, missiles, space technology, aviation, metallurgy, chemical industry, petroleum, machinery, water conservancy, electric power, transportation, meteorology, textiles, and health.
Classification
Electronic digital computers can be classified according to their purpose, the composition of basic logic circuits, the size of storage, and the speed of operation.
The use angle
From the use point of view, it can be divided into three categories: general-purpose computers, data processors and control machines.
1. General purpose machine
It is used to calculate complex mathematical problems in scientific research and engineering design (such as differential equations, algebraic equations, etc.), the law of motion of objects and the selection of the best solution. For example, calculations for missiles, satellites' trajectories, thermonuclear reactions, molecular motions, crystal structures, fluid mechanics, thermodynamics, stress, optics, etc., as well as the selection of the best solutions for the design of dams, bridges, and factory buildings.
2. Data processor
Used for comprehensive analysis of data. For example, to summarize, sort, classify and count experimental data, observation data, statistical data, and original data, automatically draw data distribution curves or automatically print reports.
3. Control machine
Also called real-time control machine, that is, actual and timely collection of detection data, after calculation and judgment, automatic control or automatic adjustment according to the best value. The control machine can be divided into direct control machine, supervisory control machine and system computer.
Circuit composition
The composition of the basic logic circuit can be divided into electron tubes, transistors, integrated circuits, and large-scale integrated circuits. Foreign countries call this division four generations. The first generation was from 1946 to 1957. The basic logic circuit was composed of electronic tubes, and the computer structure was organized around a central processing unit, using machine language. In the second generation from 1958 to 1964, the basic logic circuit was composed of transistors, the computer structure was centered on memory, the channel concept was introduced, and a series of programming languages were created. The third generation from 1965 to 1973, the basic logic circuit is composed of integrated circuits, the computer structure is still centered on the memory, and the central processing unit, channels, input and output devices are connected through the memory bus, and the software functions are greatly expanded. , The development of a human-machine dialogue language system, and the rapid development of minicomputers. In the mid-1970s, the transition to the fourth generation began. Large-scale integrated circuits were used in devices, and the structure would be organized in the concept of distributed computing. The operating system introduced databases and the rapid development of microcomputers.
Other angles
From the storage size, it can be divided into large, medium, small, supercomputer and microcomputer.
From the perspective of speed, there are low speed, medium speed, high speed, and super high speed. From the scope of use, there are general-purpose and special-purpose ones. From the representation of the number, there are fixed-point and floating-point.
In addition, from the transmission mode and operation mode, there are serial machines and parallel machines, and so on.
Composition
The computer system is based on hardware and is composed of the organic combination of hardware and software.
Hardware
Hardware is also called hard equipment. The hardware includes the host and external devices. The host is mainly composed of arithmetic unit, memory storage and controller. Peripheral equipment refers to the equipment through which information enters and takes out when handing over with the host, including basic input, output equipment, external storage, etc. In addition, there are power supplies, consoles, etc.
Software
Software is also called software equipment. Software is the general term for various programs for managing and operating machines. These programs are compiled in advance for ease of use and full use of computer performance, which are different from ordinary arithmetic programs. There are two types of software: system software and application software.