Computer (Computer) is a kind of information can be received and stored, and in accordance with the procedures stored in its internal (these procedures are the embodiment of the will of the people) on the input information processing, processing, and then the results of the output of the highly automated electronic equipment.
Two, the birth of electronic computers
1, the world's first computer ENIAC, was born in February 1946 in the United States, which does not have the main principle features of modern computers - stored programs and program control.
2, the world's first computer designed by the function of the stored program EDVAC, the United States in 1946 began to design, developed in 1950.
3, the world's first computer to realize the function of stored procedures EDSAC, the United Kingdom began designing in 1947, May 1949 into operation.
Three, the development of computers
The development of electronic computers can be divided into four stages according to the electronic logic devices:
1, the first generation of computers (from the introduction of ENIAC ~ the early 1950s), the era of electron tubes, with a light screen tubes or mercury time-delay circuits as a memory, the input and output using perforated paper tape or card. Software was in the initial stage, there was no system software, and the language was only machine language or assembly language. Applications are based on scientific computing.
2, the second generation of computers (mid-1950s ~ mid-1960s), the transistor era, the use of magnetic cores and drums for memory, the production of high-level programming language and batch processing systems. The field of application was expanded to data processing and transaction processing, and gradually used for industrial control.
3, the third generation of computers (the mid-1960s to the early 1970s), the era of small and medium-sized integrated circuits, the main memory began to use semiconductor memory, the external memory has a disk and tape, with operating systems and standardized programming language and human-computer conversational Basic language. Not only applied to scientific computing, but also applied to business management, automatic control, auxiliary design and auxiliary manufacturing and other fields.
4, the fourth generation of computers (mid-1970s to the present), the era of large-scale ultra-large-scale integrated circuits, the application of computers involved in various fields such as office automation, database management, image recognition, speech recognition, expert systems, and into the family.
Four, computer classification
Computers can be divided according to various aspects such as purpose, size or processing objects.
1, according to the use of division
(1) general-purpose machine: applicable to solve a variety of general problems, the use of this type of computer in a wide range of fields, the generality of the stronger, in scientific computing, data processing and process control and other purposes can be adapted.
(2) Specialized machines: used to solve a particular aspect of the problem, equipped with software and hardware for the solution of a problem, such as in the production process automation control, industrial intelligent instrumentation and other specialized applications.
2, according to the size of the division
(1) giant computer: used in cutting-edge defense technology and modern scientific computing. Giant machine computing speed up to a million billion times per second, the development of giant machines is an important measure of a country's economic strength and scientific level.
(2) large/medium-sized computers: have a high computing speed, can perform tens of millions of instructions per second, and have a larger storage space. Often used for scientific computing, data processing or as a network server.
(3) small computers: smaller, simple structure, lower operating environment requirements, generally used in industrial automation, measuring instruments, medical equipment in the data acquisition and so on. Small machine used as a giant computer system also plays an important role in the auxiliary machine.
(4) microcomputer: the central processing unit (CPU) using microprocessor chips, compact and lightweight, widely used in business, service industry, factory automation, office automation and mass information processing.
(5) workstation: personal computing environment and distributed network environment as a prerequisite for high-functioning computers, workstations are not simply numerical calculations and data processing tools, but also support for artificial intelligence operations of the work machine, through the network connection including workstations, including a variety of computers can be mutual transmission of information, resources, information **** enjoyment, the distribution of load.
(6) server: in the network environment for multiple users to provide services *** enjoyment of equipment, generally divided into file servers, print servers, computing servers and communication servers.
3, according to the processing object
(1) digital computer: computer processing input and output values are digital quantities.
(2) analog computer: processing data objects directly for continuous voltage, temperature, speed and other analog data.
(3) Digital-analog hybrid computer: input and output are both digital and analog data.
V. Characteristics of the computer
Computer is a highly automated information processing equipment. The main features are fast processing speed, high computational accuracy, strong memory, reliable logical judgment, high reliability and versatility.
1, fast processing speed: computer computing speed measured in terms of MIPS (how many millions of instructions per second).
2, high computational accuracy: the accuracy of the number is mainly determined by the number of bits of the binary code that represents the number.
3, memory capacity: memory can store a large amount of data and computer programs.
4, reliable logical judgment: with reliable logical judgment is an important feature of the computer, is the computer can realize the information processing automation is an important reason.
5, high reliability and versatility.
Sixth, the computer's performance indicators
The computer's main technical performance indicators are the main frequency, word length, memory capacity, access cycle, computing speed and other indicators.
1, the main frequency (clock frequency): refers to the number of pulses output by the computer CPU in a unit of time. It largely determines the operating speed of the computer. The unit MHz.
2, word length: refers to the number of bits of binary data that can be processed simultaneously by the computer's computing components. Word length determines the precision of a computer's arithmetic.
3, memory capacity: is the total number of bytes of information that can be stored in the internal memory. Can often 8 binary bits (bit) as a byte (Byte).
4, access cycle: memory for two consecutive independent "read" or "write" operation of the shortest time required, the unit to nanoseconds (ns, 1ns = 10-9s). Memory to complete a "read" or "write" operation of the time required is called memory access time (or read-write time).
5, computing speed: a comprehensive indicator, the unit is MIPS (million instructions / second). Factors affecting computing speed, mainly the main frequency and access cycle, word length and storage capacity also have an impact.
Other indicators: machine compatibility (including data and file compatibility, program compatibility, system compatibility and equipment compatibility), system reliability (MTBF), system maintainability (MTTR), the maximum number of external devices allowed to configure the machine, the computer system's Chinese character processing capacity, database management systems and network functions etc. Performance/price ratio is a comprehensive evaluation of computer performance indicators.
VII, the application of computers
The scope of computer applications, according to the characteristics of its application can be divided into scientific computing, information processing, process control, computer-aided systems, multimedia technology, computer communications, artificial intelligence.
1, scientific computing: refers to the application of computers to complete scientific research and engineering technology in the proposed mathematical problems (numerical calculations). General requirements for computer speed, high precision, relatively large storage capacity. Scientific computing is the earliest application of computers.
2, information processing: information processing mainly refers to the non-numerical form of data processing, including the collection of data and information, storage, processing, classification, sorting, retrieval and release of a series of work. Information processing, including office automation (OA), enterprise management, intelligence retrieval, newspaper layout processing. Characterized by a large amount of raw data to be processed, while the arithmetic operation is relatively simple, there are a large number of logical operations and judgment, the results require the form or file form storage, output. Requirements of the computer's large storage capacity, speed is not very demanding. Information processing is currently the most widely used, accounting for about 80% of all applications.
3, process control: the computer for science and technology, military field, industry, agriculture and other areas of process control. And computer control system, need to have a special digital - analog conversion equipment and analog - digital conversion equipment (called D / A conversion and A/D conversion). As the process control is generally real-time control, sometimes the computer speed requirements are not high, but requires high reliability and timely response.
4, computer-aided systems: 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,: the digital, text, sound, graphics, images and animation and other organic combination of media, the use of computers, communications and radio and television technology, so that they establish a logical link, and can be processed (including the entry of these media, compression and decompression, storage, display and transmission, etc.) of the technology. At present, the application areas of multimedia computer technology are being broadened, in addition to knowledge learning, e-books, business and home applications, in telemedicine, video conferencing have been greatly promoted.
6., computer communications: is a combination of computer technology and communications technology, the product of the development of computer network technology will be in different geographical areas of the computer with communication lines connected to the corresponding software, to achieve the purpose of resource **** enjoy.
7, artificial intelligence: the study of interpretation and simulation of human intelligence, intelligent behavior and its laws of a discipline. Its main task is to establish the theory of intelligent information processing, and then design can show some approximation of human intelligent behavior of the computing system. Artificial intelligence discipline includes: knowledge engineering, machine learning, pattern recognition, natural language processing, intelligent robotics and neural computing and other aspects of research.