Network Computer Network Computer (abbreviated as NC) PC is an invention that has the greatest influence on human society in recent decades. PC enables individuals to use computers conveniently and greatly expands the application of computers. But PC is not omnipotent, and it is not always the best personal computing tool. For example, in the mobile communication environment, people need a "smart phone" that is smaller, more energy-efficient and better integrated with communication. In the network application environment, people need a more compact, safer and easier to manage NC. The advantage of PC is its powerful processing power and freedom, but it also has disadvantages. In the network environment, PC is very easy to be infected with viruses or attacked by hackers, thus endangering the security of the whole network. Moreover, the security of data stored locally on PC is far less than that stored on server. Therefore, when security and management become the primary consideration of information systems, NC is more suitable as a client than PC. As a "thin client" in network system, NC mainly relies on high-speed network. At present, 100 Mbps or even Gigabit networks have become popular, and the network infrastructure supporting NC is no longer a problem. NC generally has no local external storage devices and redundant ports, and the running software and data are also concentrated on the server. As a network node, it is difficult for viruses and hackers to invade, and the security of data is greatly improved. Because NC can be managed centrally by the system administrator, one administrator can easily manage hundreds of NC. In addition, numerical control also has the advantages of low cost, no noise and high reliability. Of course, the disadvantage of NC is that it doesn't have the powerful processing power and freedom as PC, and it can't work independently, so it can't replace PC. Accurately speaking, NC and PC have their own strengths and should be complementary to meet different needs. [2] Network computer is a terminal client with PC function, such as low cost, no upgrade, no maintenance, easy operation, power management, strong security and high reliability. It can meet the needs of managers and the public for information processing and information acquisition, and it is the inevitable product of information application segmentation in various industries. Widely used in government e-government, military private network, banks, enterprises and institutions, schools, families, residential quarters and so on. Network computer is a kind of terminal equipment dedicated to network computing environment. Compared with PC, it has no storage devices such as hard disk, floppy disk drive and CD-ROM drive. It obtains resources through the network, and its application software and data are also stored on the server. Because of these characteristics, NC has the following advantages in teaching: 1, rights management: there is no storage device on the network computer terminal, and all programs run on the server, so that students' status can be easily understood, avoiding some problems such as chatting and playing games online. In addition, all the permissions of the client are also controlled by the server, and the control of running the application program and the control of logging in the computer system can be set on the server. 2. Easy to maintain: resources are obtained through the network, which is the terminal equipment in the network computing environment, and the PC system will not crash, so it is very convenient to install the operating system: 60 CNC machine tools only need to install the operating system on 3 servers, which is very fast. Installing or deleting teaching software is also very simple, just need to operate on the server side. In addition, the CNC machine tool system is simple to use, the hardware integration is stable, and there is basically no local fault. The failure rate is extremely low, which is very suitable for school use. 3. Low cost: From the software cost calculation, the network computer only needs to install the program on the server, which saves a lot of software purchase costs. For example, OFFICE2003, the price of a set of OFFICE2003 is 3 100 yuan. According to the calculation of 60 computers in a computer room, PC room needs186,000 yuan, and network room only needs 9,300 yuan. In the same way, many commercial software can be used as long as a few sets, and the cost is greatly reduced. From the hardware cost calculation, the network computer has a simple structure: there is no floppy drive, optical drive and hard disk, and the configuration price of NC is 1/3 of that of PC. In addition, the power of NC is only 15W, which is 1/20 of that of PC, saving a lot of power for users. The CNC machine tool has no hard disk, floppy drive and CD-ROM drive, and the operating system and application software are installed on the server, which only needs maintenance, while the CNC machine tool does not need maintenance, which greatly saves the cost. In a word, the advantage of NC is mainly to reduce the total cost of ownership: compared with low-cost PC, the cost of two NC's is equivalent to a low-cost PC (including the server cost allocated to each NC) under similar use effects. In other words, with the same investment, using NC can buy twice as many computers as using PC, which is of course particularly important for developing countries. In addition, hardware is not the whole cost. In an organization, the total cost of establishing, operating, maintaining and updating its computer system is called TCO, which consists of four elements: ① capital cost and non-human resource cost (including parts, electronic equipment, software cost, etc.). Technical support costs, including all labor costs including design, installation, maintenance, repair and upgrade. ③ Management expenses, including the expenses of purchasing management and technical management (managing network, server, desktop equipment, etc.). (4) the operating cost of users, that is, the time cost spent by users to learn and maintain their systems. According to Zona Research's calculation, the TCO of a system with 65,438+05 PCs after five years is $265,438+07,663, which is equivalent to $2,902 per PC per year, of which the hardware cost is only 65,438+03% of the TCO, as shown in Figure 65,438+0. However, if the same system adopts NC, due to the outstanding advantages of NC in management, upgrade, installation and maintenance, the TCO converted to each NC is only $65,438 +0.258 per year, which is less than half of that of PC. If according to the estimation of other organizations (including the famous Gartner Group), the TCO of a PC is as high as 7000-1.5000 USD per year, then the cost saved by adopting NC is much more. It can be seen that the economic benefits of adopting NC are very obvious no matter from the analysis of hardware cost or total cost of ownership. [3] 4. Strong security: the network computer has no local storage equipment and will not be infected with viruses. In addition, resources are allocated to each machine on the server, and user rights are set. Each machine is independent, does not affect each other, and is safe. There is also the phenomenon that sudden software and hardware problems on the PC lead to the loss of work data, which will not happen when using a network computer. All files applied for and stored by users are on the server, and the data on the server will not be lost whether the user exits normally or abnormally. 5. Simple operation: the network computer is easy to operate and use, because users can skillfully use it without any computer application knowledge. Users only need to do two things: 1) turn on the power; 2) Connect to the server. The switch NC is as simple as a household appliance. This is undoubtedly very convenient for students who have no computer foundation. 6. Upgrade-free: The network computer adopts a new network architecture. Compared with PC, the terminal client does not need to be upgraded at all. Both hardware upgrade and software upgrade need to be completed on the server side, which saves a lot of manpower and material resources. 7. Low noise: The network computer has no mechanical moving parts such as hard disk, CD-ROM drive, floppy disk drive, etc., and the embedded CPU used has low calorific value, so it doesn't need fan to dissipate heat, so it works very quietly and has no noise. Very suitable for school applications. [4] The computer used on the network, but with the traditional hard disk, floppy disk, optical disk and other components removed, belongs to a thin PC, and the server provides programs or storage on the network. The network computer has its own processing power, but all software except the core software needs to be downloaded from the network server. Because all the data used are stored on the server, frequent software upgrades and maintenance are omitted, and the cost is also reduced. NC (network computer) network computer, also called thin client, was put forward by Oracle Company in 1995. At that time, it caused great repercussions in the computer and communication fields, and in the same year, the "Network Computer Alliance" was established. Subsequently, IBM, Apple, Netscape, Oracle, Sun and other five major manufacturers jointly released the NC industry standard-the brief features of network computer reference (NC- 1 specification for short), which includes specifications supporting Java, HTML, FTP, TCP/IP and CGI. More than 70 manufacturers, including the world's largest consumer and commercial electronic equipment manufacturers, communication manufacturers, software developers, wireless system manufacturers, microprocessor manufacturers, peripheral manufacturers and credit card companies, immediately expressed their support for the formulation of this technical specification. NC mode is a brand-new C/S mode, which is very popular in Europe and America. The NC mode is called Terminal Services and WINDOWS-based Terminal (WBT). Except for hard disk, optical drive and floppy drive, NC is no different from PC. There are motherboard, memory, network card, graphics card, mouse and keyboard interface, parallel port, serial port and USB port. The working mode adopted by NC is C/S (Client/Server) mode. Because there is no hard disk, the data used by the terminal is placed on the server. After NC logs in to the server, the server will send a set user interface and some applications suitable for users to the terminal. The server will receive the mouse and keyboard commands sent by the terminal to operate, and then send the image of the operation result back to the terminal for display. Using NC to do the work, all the upgrade work and management and maintenance work are concentrated on the server side. The prospect of Linux and network computer NC in desktop computers is quite controversial. From a global perspective, the development of Linux in this area is not fast, and now it only accounts for about 5% of desktop computers, so some people doubt its future in this area. It seems that in developed countries, Linux can hardly compete with Windows in the field of desktop computers, but in China, the situation is different. Because PC is far from being popular in China, a new desktop computer, network computer or network computer (NC), is emerging under the impetus of the Internet, which will be the main way for Linux to expand its share in the desktop computer field. The meaning of products in the IT field often changes with time. When 198 1 was first introduced, it was only IBM's personal computer. Today, PC can cover all Wintel computers, including desktop computers, portable computers, workstations and servers. Similarly, the meaning of NC changes with time. When Ellison and others in Oracle Bone Inscriptions put forward the concept of NC in 1995, NC was basically closely related to Java applications. However, the popularization of Java is not as smooth as expected. For example, Corel had planned to rewrite all its office software in Java, but soon gave up. Similarly, NC that relies entirely on Java has also failed. If we want a new definition of NC today, we can describe it as follows: NC is a thin client dedicated to broadband network computing environment, in which applications and data are stored on the server. NC itself has no external memory (hard disk, CD, etc.). ) and few expansion ports except the display and input devices necessary for human-computer interaction. NC supports various working modes and application software including Windows, Unix, Linux and other platforms. Ncs are mostly non-Wintel structures. This definition shows that NC generally has an Ethernet port with the rate of 10/ 100Mbit/S; "Applications and data are stored on the server", which is the development trend of IT industry including Microsoft. Net strategy. According to the actual needs, the input devices of NC are only keyboard and mouse, and there are many authentication devices such as password keyboard and IC card reader. It should be pointed out that the current NC can support multi-mode and cross-platform, which is a new development of technology in the near future. It breaks the limitation that NC only supports Java at first, so that NC can use Windows application software on the server, which is beneficial to the popularization of NC. Because the architecture of NC itself is not required to be compatible with Wintel, from the perspective of information security and cost performance, NC will be "mostly non-Wintel structure". When NC is popularized in the future, some Wintel-structured PCs may be "slimmed down" into "thin PCs" (that is, some devices on PCs are removed) to compete with NC. At this time, the advantage of NC over "thin PC" will mainly be its non-Wintel structure. If NC is also Wintel architecture, it will not be much different from "thin PC" and can even be regarded as an extension of PC. Therefore, the important reason why NC can become a new desktop computer is that NC is mostly non-Wintel, while PC is Wintel. Although some NC in the market can't reach the level described here, such NC can be realized with the current technology, so it will appear in the market soon. People will ask, since NC has so many advantages, why not popularize it? In fact, we have mentioned that NC took a detour a few years ago; Moreover, the popularity of high-speed network environment is something in recent years. The technology of numerical control itself is also developing. For example, now NC can use Windows programs running on the server, which is a terminal of Windows and needs the server to support "multi-user", which is a function only available above NT 4.0. In addition, the most reasonable working mode of NC is B/S (browser/server), which is no different from PC, that is, running the browser locally and running the application on the server, but this mode has only developed in recent years and has become the mainstream of application. In the future, with the development of network computing environment, the popularity of NC is a matter of time. The application scope of NC and PC shows that these two types of computers are complementary. Some applications are suitable for PC, some applications are suitable for NC, and some applications can be used by both computers. In the future, these two kinds of computers can be mixed in one unit. In short, for a long time, these two kinds of computers will coexist and compete with each other in some cases, which is not a bad thing for users. Instead, it gives users more choices and promotes the continuous improvement of the cost performance of these two types of computers. The benefits of using Linux in NC are the same as those in server and other fields, but it is worth noting that using Linux in NC also brings some special benefits, mainly that NC can adopt non-Wintel structure. In other words, Linux enables non-Intel CPU to be supported by a mature OS, and enables non-Wintel computers to survive and develop. People must remember that in the mid-1990s, Motorola tried to make a personal computer with PowerPC chips. Although the performance of PowerPC chip exceeded Intel's CPU at that time, the plan was aborted because Microsoft's Windows did not support PowerPC. There is a PowerPC personal computer production line somewhere in China, which was abandoned just after it was built without producing a computer. Therefore, the reason why Intel CPU can monopolize the PC field is entirely because of the support of Microsoft OS. Conversely, CPU of any structure will never enter the PC field without the support of Microsoft OS. Now with open source Linux, it can be easily transplanted to any kind of CPU, and it can be supported by a large number of application software on Linux immediately, so that this new structure of CPU can survive and develop. Because of this, non-Wintel NC can also be developed. For China, this means that it is possible for us to develop a CPU with independent intellectual property rights, and with the support of Linux, we can form an NC with independent core technology, and of course we can also form various other IA devices. Therefore, Linux has created the necessary conditions for us to develop CPU with independent intellectual property rights, and people will gradually realize the significance of popularizing Linux in this respect. Imagine that without Linux, even if a CPU is developed, there is no mature OS support (of course, Microsoft can't transplant Windows for this). Such a CPU can only be a hero's useless place. People may ask, why not develop a CPU compatible with Intel architecture? So you can run Windows? The answer is no, mainly for two reasons: one is the technical difficulty, and the other is the intellectual property barrier, which makes this road impossible. It can be seen that Linux is the premise of developing CPU with independent intellectual property rights and non-Wintel structure NC. China has a huge market, and China's PC is far from saturated. Now it has entered the Internet era. The rise of Linux will make Wintel PC and non-Wintel NC*** coexist in the field of desktop computers in China. In the future, with the development of Internet and independent core technologies, the share of numerical control will become larger and larger, and the field of desktop computers in China will definitely be different from that in western developed countries. The main application fields of NC are the State Council Information Work Office, Ministry of Science and Technology and Ministry of Information Industry. In the Technical Guide of E-government Engineering issued in early 2003, it is stipulated that "network computers are recommended for window service industries and internal office systems with centralized business management and high security requirements". It is emphasized here that NC is mainly used in window service industry and internal office system. Although the internal office system can also use PC, the security of PC is poor, even if the internal and external networks are "physically isolated", it is not safe. At present, wireless Internet access has become a routine function of notebook computers, and wireless access points abound. The ubiquitous wireless connection makes "physical isolation" difficult to achieve. Unless all notebooks are not used, all wireless access devices on the computer are removed, or the whole workplace is shielded, "physical isolation" is empty talk. Obviously, these hidden dangers can be eliminated if NC is adopted. Window service industry is very common, such as finance, insurance, taxation, transportation, postal service, … these application systems all contact customers through business windows. As the front end of this kind of application system, "window business" is basically fixed (one or several services), and its main functions are: interacting with customers, verifying identity, preparing bills, etc. Usually, a business "window" needs some local processing and storage capabilities: it can input data and display it to realize interaction; Able to communicate with back-end system; Be able to prepare the required bills: be able to connect devices for identity verification (such as password keyboard, card reader, biometric equipment, etc.). ). At present, the requirements of information system for information security are getting higher and higher, and the number of business windows is very large, which directly faces our customers. Therefore, improving the security and manageability of business windows has become a major problem in information systems. Historically, the service "window" was composed of character terminals, which were used as time-sharing terminals of background hosts. This character terminal is very fragile and easy to manage. Later, with the decline of host system and the rise of PC, PC gradually became the protagonist of window business. PC is powerful, and it can handle window business more than enough, but it is unsafe and difficult to manage. In this kind of application, the rich functions of PC are often harmful, so it is very reasonable for the window service industry to choose NC. Widely used in government, enterprises and institutions, finance and other industries, network office, rural informatization, hotel room computers, school electronic classrooms and digital libraries.