Internet 互联网


  The Internet is a giant network of computers located all over the world that communicate with each other.

   The Internet is an international collection of computer networks` that all understand a standard system of addresses and commands, connected together through backbone systems. It was started in 1969, when the U.S. Department of Defence established a nationwide network to connect a handful of universities and contractors. The original idea was to increase computing capacity that could be shared by users in many locations and to find out what it would take for computer networks to survive a nuclear war or other disaster by providing multiple path between users. People on the ARPNET (as this nationwide network was originally called) quickly discovered that they could exchange messages and conduct electronic "conferences" with distant colleagues for purposes that had nothing to do with the military industrial complex. If somebody else had something interesting stored on their computer, it was a simple matter to obtain a copy (assuming the owner did not protect it).

  Over the years, additional networks joined which added access to more and more computers. The first international connections, to Norway and England, were added in 1973. Today thousands of networks and millions of computers are connected to the Internet. It is growing so quickly that nobody can say exactly how many users "On the Net".

  The Internet is the largest repository of information which can provide very very large network

The Wonderful Structure of a Microcomputer


      In Chinese, a computer is popularly known as an " electrical brain", for the working process of a computer is similar to a human brain very much.

In appearance, a microcomputer has three simple and apparent parts: the main frame, the keyboard and the monitor. In other words, if you own these parts, you would exactly have a computer. A computer system is composed of software and hardware in the light of its working mode. If we compare the hardware to a human body, then, the software would be soul.

Just as a driver can't drive a car without driving skills or the car itself, you can't control a computer without controlling techniques or the computer itself. The controlling techniques are called software, while computers themselves and related devices are called hardware.

The work of a computer is just making full use of various resources by software set in the computer, and directing the hardware to realize marvelous omnipotent functions.

Primary Components of a Microcomputer


       There are many types of microcomputers. Here, we will use an IBM Personal Computer (PC) to illustrate the primary components of a microcomputer. Other brands and models of microcomputers exhibit difference in appearance and operations. An IBM PC is shown in the figure. Its primary hardware components are the main frame, the monitor, the keyboard, and many peripherals such as the disk drive, hard disk, printer, and mouse, all of which are hardwired to the main frame. The main frame is the heart of a microcomputer system. It contains the Central Processing Unit (CPU), a chip that controls the major operations of the computer and the main memory.

Floppy and Hard Disks


      The typical secondary storage medium of a microcomputer is the floppy and hard disks. A floppy disk, or diskette, is a thin circular piece of flexible polyester coated with a magnetic material. The data are recorded on a series of concentric circles called tracks. The access mechanism steps from track to track, reading or writing one track at a time. A track is subdivided into sectors. To distinguish the sectors, they are sequentially addressed by natural numbers 0,1,2and so on .A sector is a primitive access unit.Most microcomputers use floppy diskettes of 5 1/4 inches and 3 1/2inches in diameter. The following figure shows a 3 1/2 inches floppy diskette. Hard disks, or fixed disks, can be either fixed in the mainframe as a part of the internal hard disks reside permanently within the microcomputer and are removed only for servicing or replacement. External hard disks can be purchased alone and then attached to the microcomputer with cables; they are used for backing up large amounts of data or for additional storage capacity. Hard disks provide tremendous storage capacities ranging from hundreds of megabytes to several gigabytes.

Keyboard　and Mouse


       A keyboard is a requisite hardware device of a computer. It is an input device most in use, and a dialogue tool between a man and a computer. We can input data needed to be processed or preserved by a computer via a keyboard. A typical includes a group of standard keys set in the center of the keyboard, many function keys and several additional keys. Function and additional keys have different roles in different software. Another popular input device is mouse. The mouse is a small, handheld object that is pushed around a desktop to move the cursor on the screen or to select choices from menus displayed on the screen. A mouse is essentially a pointing device that allows the user to do many operations more quickly than he could with the keyboard alone.

Monitor


       The monitor is an essential output device of a microcomputer. Monitors, also known as video display terminals (VDTs), resemble television screens, and may be either monochrome or color. A monochrome monitor displays only one color on the screen. It is possible white or more eyepleasing green. While color monitors usually offer a wide selection of display colors.

Printer


        The printer is the most commonly used output device after the monitor. Printers can create a permanent paper copy of results generated by the program being run on the computer. These printouts are sometimes referred to as hard copy. Printers can also generate listings of programs and graphic images. Three types of printers are available: wire printers, ink jet printers and laser printers.

Computer Hardware


    A computer is a fast and accurate symbol processing system. It can accept, store, process data and produce output results. A computer can automatically process data without human intervention. However, it must be given a set of instruction to guide it, step by step, through processes. The set of instructions is called a program, The program is stored physically inside the machine, making it a program.

    All computer systems of interest to us are similar. They contain hardware components for input, central processing unit and output. The system on the small-scale is called a microcomputer or minicomputer. Continuing up the size scale, the mainframe computer is one that may offer a faster processing speed and a greater storage capacity than a typical mini. Finally comes the supercomputer, designed to process complex scientific applications, which is the largest and fastest.

Computer Hardware


Although the capacity of computers’ storage locations is varied, every computer stores numbers, letters, and other characters in a coded form. Every character in the storage is represented by a string of 0s and 1s, the only digits founded in the binary numbering system.  BCD and ASCII are popular computer codes.

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Computer software


    Most people think of software as all of the amazing application programs available today for microcomputers. But there are other forms of computer software that make it possible to use application programs. Software is the collective name for all the programs and instructions that direct a computer’s operations. Generally software can be divided into three types: system software, application software and support software, system software monitors and controls the system’s hardware. Application software performs specific tasks for the user. Support software is a series of software, which support development and maintenance of other software. Software is created through the use of programming languages.

The computer Language


   The role of a program is to deliver user’s intention to a computer and direct it to work. That is to say, a program is a dialogue tool for interacting between a man and a computer, as well as a bridge to transmit information. In general, the characters, phases and their syntax rules for programming are generally called “programming language”.

    Programming languages are divided into three types: machine language, which is also called an instruction system, is the only one used directly by computers. The assembler language is a kind of symbolic language. It adopted some mnemonic symbols which can show the instructional functions to present the content of the program. The high-level language is a programming language based on English. Its operators and expressions are similar to ordinary mathematical formulas. General users can easily master a high-level language and make programs in it.

Programming


   Programming is, at its simplest, the way people tell computers what to do, when to do it, and how to do it. A program is a specific set of instructions written by one or more people, which direct the action of a computer system. It may be a very simple or complicated set of instructions. It may be written by a beginning computer user or by a top computer expert. It may be written in simple English or in a language spoken only by computers. Just as writing a fiction, programming is a process of creating art.

What is Object Oriented Programming?


    Object oriented programming (OOP) is a new way of approaching the job of programming that differs from traditional programming because it uses objects as data structures to enhance productivity, simplify programming, get reusability and improve software reliability. All object oriented programming languages have three characteristics in common: objects, polymorphism and inheritance. Let’s take a look at these concepts.
    Object is a data structure that contains both structured information and related operations. An object can contain other objects. In this way, the object is given both data properties and behaviors, and so object oriented programs can better reflect the real world they are trying to simulate. Polymorphism essentially means that one name can be used for several related but slightly different purposes. Inheritance is the process by which one object can acquire the properties of another object. This is important because it supports the concept of classification. For example, a red delicious apple is a part of the classification apple, which in turn is a part of the fruit class, which is under the larger class food.  

Office Automation


      Office Automation (OA) is the application of the computer and communication technologies to improve the productivity of clerical and managerial office workers, The major functions of the OA system include text processing, electronic mail, information storage and retrieval, task management, and etc.. Today, there have been many OA systems, for example, desktop publishing, video conference, videotext and so on. So, many office workers can easily find the information they want through a personal computer sitting on his or her desk, It changes substantially the way people work in an office.

Artificial Intelligence


      For many years, researchers have been exploring the way people think in hopes of creating a computer that thinks like a person. This is so called Artificial Intelligence (AI). It aims at producing a computer system that will be able to communicate with us by speech and hearing, and be capable of solving intelligent problems. One practical application of AI has been in the area of expert systems. An expert system is a computer program that solves the specialized problems at the level of a human expert.

Expert System


       An expert system is a software system having some domain knowledge, which can solve some problems for people. Its performance depends on the facts and the rules that are fed into the computer. The expert knowledge is gathered by knowledge engineers from human experts in the field such as medicine, engineering, or geology. For example, in the field of medicine, one question that might be asked of an expert system is whether one treatment is better for a patient than another one. An expert system has the capacity to store the collection of knowledge and manipulate it in response to user’s inquiries, in some cases, it can explain responses to the user.

Internet has four main applications as follows：


    l．E－mail． With Internet， people can compose， send， and receive electronic mails． Many people get dozens of messages a day and consider it as their primary way of interacting with the outside world, far outdistancing the telephone and snail mail.
    2．News． Newsgroups are specialzied forums in which users with a common interest can  exchagne messages．Thousands of newsgroups exist on Internet，on technical and nontechnical topics，including computers，science，recreation，and politics．
    3．Remote login．Using the Telnet，Rlogin, or other programs， the  user anywhere on  Internet can log into any other machine  on  which  he  has  an  account．
    4． File transfer．Using the FTP program， it is possible to copy files from one machine on Internet to another． Vast numbers of articles， databases， and  other information are available in this way．

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