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A computer is a fast and accurate symbol manipulating system that is organized to accept, store, and process data and produce output results under the direction of a stored program of instructions. Key elements in this system include input, processing, and output devices. Let's examine each component of the system in more detail.
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Input Devices Computer systems use many devices for input purpose. Some INPUT DEVICES allow direct human/machine communication, while some first require data to be recorded on an input medium such as a magnetizable material. Regardless of the type of device used, all are components for interpretation and communication between people and computer systems.
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Central Processing Unit The heart of any computer system is the central processing unit(CPU). There are three main sections found in the CPU of a typical personal computer system:The primary storage section, The arithmetic- logic section, and The control section. But these three sections aren't unique to personal computer: They are found in CPUs of all sizes.
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Output Devices Like input units, output devices are instruments of interpretation and communication between humans and computer systems of all sizes. These devices take output results from the CPU in machine-coded form and convert them into a form that can be used (a)by people (eg. a printed and/or displayed report)or (b)as machine input in another processing cycle.
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The input/output and secondary storage units sometimes called peripheral devices (or just peripherals). This terminology refers to the fact that although these devices are not a part of the CPU, they are often located near it.
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计算机是一种能接收、存储和处理数据，并能在存储指令程序控制下产生输出结果的快速、精确的符号加工系统，这一系统是在存储指令程序控制下工作的。本节说明为什么计算机是一个系统以及计算机系统是如何组成的。系统的主要部件包括输入设备、处理器和输出设备。现在详细介绍每一部件。
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输入设备 计算机系统使用多种输入设备。其中有些输入设备直接进行人－机通信，另一些则首先要求把数据记录在诸如磁性材料那样的输入介质上。不论使用哪种设备，所有这些都是人与计算机系统之间进行解释和通信的部件。
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中央处理器 中央处理器（CPU）是计算机系统的核心。一台典型个人计算机的CPU由三部分组成：主存储器部分、算术－逻辑部分和控制部分。不仅个人计算机如此，各种规模的计算机的CPU都有这三部分。
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输出设备 与输入设备类似，输出设备也是人与计算机系统之间的解释和通信的设备。输出设备从CPU中取出机器代码形式的结果，然后将其转换成人们可读的形式（如打印或显示报告）或另一处理周期的机器输入。
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有时也将输入／输出设备和辅助存储器称为外围设备，这是因为这些设备不属于CPU，但又位于CPU附近。
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A processor is a functional unit that interprets and carries out instructions． Every processor comes with a unique set of operations such as ADD， STORE， or LOAD that represent the processor's instruction set． Computer designers are fond of calling their computers machines， so the instruction set is sometimes referred to as machine instructions and the binary language in which they are written is called machine language！
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An instruction is made up of operations that specify the function to be performed and operands that represent the data to be operated on. For example, if an instruction is to perform the operation of adding two numbers, it must know (l)what the two numbers are and (2)where the two numbers are. When the numbers are stored in the computer's memory, they have an address to indicate where they are, so if an operand refers to data in the computer's memory it is called an address. The processor's job is to retrieve instructions and operands from memory and to perform each operation. Having done that, it signals memory to send it the next instruction.
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A processor is composed of two functional units—a control unit and an arithmetic/logic unit, and a set of special workspaces called registers. The control unit is the functional unit that is responsible for supervising the operation of the entire computer system. The control unit fetches instructions from memory and determines their type or decodes them. It then breaks each instruction into a series of simple small steps or actions. By doing this, it controls the step-by-step operation of the entire computer system. The arithmetic /logic unit (ALU)is the functional unit that provides the computer with logical and computational capabilities. Data are brought into the ALU by the control unit, and the ALU performs whatever arithmetic or logic operations are required to help carry out the instruction. A register is a storage location inside the processor. Registers in the control unit are used to keep track of the overall status of the program that is running. Control unit registers store information such as the current instruction, the location of the next instruction to be executed, and the operands of the instruction. In the ALU, registers store data items that are added, subtracted, multiplied, divided, and compared. Other registers store the results of arithmetic and logic operations.
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处理器是解释并执行指令的功能部件。每个处理器都有一个独特的诸如ADD、 STORE或LOAD这样的操作集，这个操作集就是该处理器的指令系统。计算机系统设计者习惯将计算机称为机器，所以该指令系统有时也称为机器指令系统，而书写它们的二进制语言叫作机器语言。
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指令由操作码和操作数组成，操作码指明要完成的操作功能，而操作数则表示操作的对象。例如，一条指令要完成两数相加的操作，它就必须知道：①这两个数是什么？②这两个数在哪儿？当这两个数存储在计算机内存中时，则应有指明其位置的地址，所以如果操作数表示的是计算机内存中的数据，则该操作数叫作地址。处理器的工作就是从存储器中找到指令和操作数，并执行每个操作，完成这些工作后就通知存储器送来下一条指令。
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处理器由两个功能部件（控制部件和算术逻辑部件）和一组称为寄存器的特殊工作空间组成。控制部件是负责监督整个计算机系统操作的功能部件。控制部件从存储器中取出指令，并确定其类型或对之进行译码，然后将每条指令分解成一系列简单的、很小的步骤或动作。这样，就可控制整个计算机系统一步一步地操作。算术逻辑部件（ALU）是为计算机提供逻辑及计算能力的功能部件。控制部件将数据送到算术逻辑部件中，然后由算术逻辑部件完成执行指令所需的算术或逻辑操作。寄存器是处理器内部的存储单元。控制部件中的寄存器用来跟踪正在运行的程序的总体状态，它存储如当前指令、下一条将执行指令的地址以及当前指令的操作数这样一些信息。在算术逻辑部件中，寄存器存放要进行加、减、乘、除及比较的数据项，而其他寄存器则存放算术及逻辑操作的结果。
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Summary of Operating System
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Operating systems have developed over the past thirty years for two main purposes. First, they provide a convenient environment for the development and execution of programs. Second, operating systems attempt to schedule computational activities to ensure good performance of the computing system.
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Initially, computers were used from the front console. Software such as assemblers, loaders, and compilers improved on the convenience of programming the system, but also required substantial set-up time. To reduce the setup time, operators were hired and similar jobs were batched together.
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Batch systems allowed automatic job sequencing by a resident monitor and improved the overall utilization of the computer greatly. The computer no longer had to wait for human operation. CPU utilization was still low, however, because of the slow speed of the I/O devices relative to the CPU. Off-line operation of slow devices was tried.
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Spooling also provides a pool of jobs which have been read and are waiting to be run. This job pool supports the concept of multiprogramming. With multiprogramming, several jobs are kept in memory at one time； the CPU is switched back and forth between them in order to increase CPU utilization and to decrease the total real time needed to execute a job.
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Multiprogramming, which was developed to improve performance, also allows time sharing. Time-shared operating systems allow many users(from one to several hundred)to use a computer system interactively at the same time.
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A real-time system is often used as control device in a dedicated application. Sensors bring data to the computer. The computer must analyze the data and possibly adjust controls to modify the sensor inputs. Systems which control scientific experiments, medical computer systems, industrial control systems, and some display systems are real-time systems. A real-time operating system has well-defined fixed time constraints.
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在过去30年间操作系统主要朝着两个目标发展：第一，为程序的开发和执行提供一个方便的环境；第二，操作系统试图通过对计算任务的调度以确保计算系统的良好性能。
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最初，计算机只能通过控制台使用。诸如汇编程序、装入程序及编译程序这样的软件使系统软件编程更方便，但同时也需要大量的启动时间。为减少启动时间，计算机工作就需要操作员，且将相同的一批作业排在一起。
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批处理系统通过一个驻留内存的监控程序使得作业自动排列，同时也大大提高了计算机的整机利用率，计算机不再需要等待人工操作。但是，由于I/O设备的速度相对于CPU仍然很低，因此CPU的利用率仍很低，于是就采用低速设备的脱机操作。
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假脱机（SPOOLING）系统同时还提供了一个作业池，其中的作业已读出并等待运行，这个作业池支持多道程序设计的概念。在多道程序下，几个作业可同时保存在内存中，CPU在它们之间来回服务，以便提高CPU的利用率，减少执行一个作业实际所需的总时间。
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为提高系统性能而开发的多道程序设计技术同样也允许分时。分时操作系统允许多个用户（从一个到几百个）同时交互使用一个计算机系统。其他操作系统类型包括实时系统和多处理机系统。
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实时系统常用作专用系统中的控制设备。传感器将数据传到计算机系统，计算机应分析数据并尽可能调整控制以修改该传感器的输入。控制科学实验的系统、医学计算机系统、工业控制系统以及一些显示系统都是实时系统。实时系统有严格定义的、固定的时间限制，处理过程应在规定的时间内完成；否则系统失效。
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Given the fundamental language of communication with a computer—namely, machine language—there exists an almost intolerable barrier between the person who desires to solve some problem using the computer and the description of the solution in terms of the machine language.
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The development of symbolic languages and assemblers was followed closely by the development of autocoders, in which the programmer's language was more closely related to mathematical notation than to the machine operations. However, the autocoder required the development of more sophisticated conversion processors, thus leading to a study of the general translatory process.
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The methods of program conversion and subsequent execution of a user's program can be classified into two basic techniques: compilation and execution, or interpretation.
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translate To transform statements from one language to another without significantly changing the meaning. In this sense, a programmer must insist that a compiler or the conversion process within an interpreter should be a translator, since the meaning associated with a source program must be carried over to the target language program.
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compile To prepare a machine language program from a computer program written in another programming language by making use of the overall logic structure of the program, or generating more than one machine ［language］ instruction for each symbolic statement, or both, as well as performing the function of an assembler.
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interpreter A computer program that translates and executes each source language statement before translating and executing the next one.
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In practice, there rarely exists a compiler or an interpreter which adheres precisely to these definitions； most languages possess certain features that cannot be compiled, and most interpreters initially preprocess the source program into some intermediate form from which the original program can be reconstructed, and operate upon that code rather than the original form.
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如果只基于计算机通信的原始语言——机器语言，则在用计算机解决某一问题的人与用机器语言来对解决该问题的方法进行的描述之间存在一个几乎令人不能容忍的障碍。
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随着符号语言和汇编语言的研制与开发，紧接着出现了自动编码器，这样，程序员用的语言与数学表达的联系比与机器操作的联系更加紧密。然而，自动编码器需要开发更复杂的转换处理程序，于是导致了对于一般翻译过程的研究。
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程序翻译及随后的用户程序的执行方法，可归类为两大基本技术，即编译和执行或解释。
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翻译：对语句进行从一种语言到另一种语言的变换，而不改变（句子的）意义。在这一意义上，程序员必须坚持做到使一个编译程序或一个解释程序中的翻译过程是一个翻译器，因为与源程序有关的意义必须转移到目的语言程序中。
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编译：利用程序的总体逻辑结构，将用其他语言书写的计算机程序翻译成机器语言程序；或为每一符号化语句产生多于一个的机器语言指令，或同时具有以上两种形式，并执行汇编程序的功能。
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解释程序：在翻译并执行下一语句前，翻译并执行每一当前源语言程序语句的计算机程序。
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实际上，很少有完全遵循这些定义的编译程序或解释程序；大多数语言具有某些不能被编译的特征，而大多数解释程序首先对源程序进行预处理，处理成某一中间形式，再由该中间形式重新构造原始程序，并在该重新构造的代码上而不是在原始形式上运行。
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The OSI reference model, sometimes also called ISO or 7 layers reference model for communication, has been developed by the International Standards Organization in early 1980's. Hence the interchangeable terms OSI/ISO Reference Model. This model describes the principles for interconnection of computer systems in an Open System Interconnection environment. So, it is an idealized model of the logical connections that must occur in order for network communication. Most protocol suites, such as TCP/IP, DECnet, and Systems Network Architecture (SNA), map loosely to the OSI reference model. The OSI model is not a protocol but it is good for understanding how various protocols within a protocol suite function and interact. But what does it really mean"Open System Interconnection"？ The general principle which leads to the definition of the OSI standard was to allow connection and communication between any computer systems (from any vendors) as long as they comply with this"OPEN"standard.
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OSI参考模型，有时也称为OSI或者7层通信参考模型，是在20世纪80年代初由国际标准化组织开发的。因此，还可称为OSI/ISO参考模型。这个模型描述了在开放系统互联环境中计算机系统互联的若干原则。因此，它是一个适合于网络通信的理想的逻辑连接模型。许多协议簇，如TCP/IP、DECnet和系统网络体系结构（SNA），都不太严格地映射为OSI参考模型。OSI模型不是一个协议，但是它有助于理解一个协议簇中的各种协议是如何运行和相互作用的。"开放系统互连"真正意味着什么呢？OSI标准定义的总体原则是只要它们遵守这个"开放"标准，任何计算机系统（来源于任何厂商）之间都可以进行连接和通信。
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Database Technology on the Web
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Today's DBMS technology faces yet another challenge as researchers attempt to make sense of the immense amount of heterogeneous, fast-evolving data available on the Web. The large number of cooperating databases greatly complicates autonomy and heterogeneity issues and requires a careful scalable approach. We need better models and tools for describing data semantics and specifying metadata. Techniques for automatic data and metadata extraction and classification (ontologies, for example) Are crucial for building tomorrow's Semantic Web. Query languages and query processing should also be extended to exploit semantic information.
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Users also need adaptive systems to help them explore the Web and discover interesting data sources and interfaces that support different query and search paradigms. Data dissemination techniques and notification services must be developed to enable effective data delivery services. Web-centric applications such as e-commerce and digital government applications pose stringent organizational, security, and performance requirements that far exceed what is now possible with traditional database techniques. Recent XML-native or extended DBMSs still need to be fine-tuned and evaluated. Finally, we need new methodologies to support the design and development of data-intensive Web sites.
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随着研究人员试图弄懂网上大量不同种类组成的、快速演化的数据的意义，今天的数据库管理系统技术还面临着另外一个挑战。大量的协作式数据库使自主性与异构性问题大大复杂化了，这需要一种详细的、可扩展的方法。需要用更好的模型和工具来描述数据语义并规定元数据。用于自动数据和元数据抽取和分类（如存在论）的技术对建立明天的语义网络至关重要。查询语言和查询过程也应扩充到能采用语义信息。
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用户也需要适应性的系统以帮助他们探索网络、发现支持不同查询和搜索范例的有趣数据源和界面。为了使数据传送服务更加有效，必须发展数据传送技术和报告服务业务。以网络为中心的应用，如电子商务和数字政府应用等，对组织、安全和性能提出了严格的要求，这些要求远远超出了目前传统数据库技术的可能性。目前本身就有XML或扩展的数据库管理系统仍需要进一步精化和评价。最后，需要一套新的方法来支持数据密集型网站的设计和开发。
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Database Management Systems(DBMS)
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You know that a data base is a collection of logically related data elements that may be structured in various ways to meet the multiple processing and retrieval needs of organizations and individuals. There's nothing new about data bases-early ones were chiseled in stone, penned on scrolls, and written on index cards. But now data bases are commonly recorded on magnetizable media, and computer programs are required to perform the necessary storage and retrieval operations.
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You'll see in the following pages that complex data relationships and linkages may be found in all but the simplest data bases. The system software package that handles the difficult tasks associated with creating, accessing, and maintaining data base records is called a data basemanagement system (DBMS). The programs in a DBMS package establish an interface between the data base itself and the users of the data base. （These users may be applications programmers, managers and others with information needs, and various OS programs. ）
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A DBMS can organize, process, and present selected data elements from the data base. This capability enables decision makers to search, probe, and query data base contents in order to extract answers to nonrecurring and unplanned questions that aren't available in regular reports. These questions might initially be vague and/or poorly defined, but people can"browse"through the data base until they have the needed information. In short, the DBMS will"manage"the stored data items and assemble the needed items from the common data base in response to the queries of those who aren't programmers. In a file- oriented system, users needing special information may communicate their needs to a programmer, who, when time permits, will write one or more programs to extract the data and prepare the information. The availability of a DBMS, however, offers users a much faster alternative communications path.
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众所周知，数据库是逻辑上相关的数据元的集合。这些数据元可以按不同的结构组织起来，以满足单位和个人的多种处理和检索的需要。数据库本身不是什么新鲜事一一早期的数据库凿在石头上、记在名册上以及写入索引卡中。而现在，数据库普遍记录在可磁化的介质上，并且需要用计算机程序来执行必需的存储和检索操作。
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在后文中你将看到除了最简单的以外，所有数据库中都有复杂的数据关系及其链接。处理与创建、访问以及维护数据库记录有关的复杂任务的系统软件包叫作数据库管理系统（DBMS）。DBMS软件包中的程序在数据库及其用户间建立了接口（这些用户可以是应用程序员、管理员以及其他需要信息和各种操作系统的人员）。
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DBMS可组织、处理和显示从数据库中选择的数据元。该功能使决策者可以搜索、试探和查询数据库的内容，从而对在正式报告中没有的、不再出现的且无计划的问题作出回答。这些问题最初可能是模糊的并且／或者是定义不清的，但是人们可以浏览数据库直到获得问题的答案。简言之，DBMS将"管理"存储的数据项，并从公共数据库中汇集所需的数据项以回答那些非程序员的询问。在面向文件的系统中，需要特定信息的用户可以将他们的要求传送给程序员。该程序员在时间允许时，将编写一个或多个程序以提取数据和准备信息。但是，使用DBMS可为用户提供一种更快的、用户可选择的通信方式。
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Multimedia is not a new word. In fact, the concept of multimedia has been around for years. However, it appears that multimedia has finally started to play an increasingly important role in today's computer world. Because of ever more powerful computer systems and the experience of creative programmers, multimedia is truly changing the way people are using computers.
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The word"multimedia"has turned into a type of two-edged sword. Although most computer professionals have heard the word, many don't know exactly what it means. This is especially true when the word is applied to everything from talking games to voice-controlled television sets. Essentially, multimedia is the integration of text, audio sound, static graphicimages, animations, and full-motion video. Multimedia may use some or all of these aspects of communication.
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Multimedia is not a product； rather, it is a technology (or more accurately a combination of technologies). A technology is anything that makes something else more efficient.
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Interactive multimedia is another buzzword going through the industry. It is nothing more than an application that gets input from the user. A book is not very interactive, and neither is television. Because of the inclusion of a keyboard and a mouse, a multimedia computer is built for user input. That makes personal computers the premier interactive multimedia machines of today.
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多媒体不是个新词，实际上，多媒体的概念已出现好几年了，然而，直到最近多媒体才在当今计算机世界中扮演重要角色。由于更强大的计算机系统和有创造性程序员的努力，多媒体确实正在改变人们使用计算机的方式。
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多媒体一词现在已变成一种双刃剑。大多数计算机专业人员都听说过它，但并不确切了解它的含义，尤其是当从声控游戏到声控电视机等任何事情都用多媒体这个词时更为明显。实质上，多媒体是文本、声音、静态图像、动画和全动态视频的集成。多媒体可能部分或全部使用这些通信方式。
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多媒体不是产品而是一种技术（更确切地说是合成技术）。技术就是使其他事情做起来更有效的东西。
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交互式多媒体是工业界的另一焦点，它无非是一种接收用户输入的应用程序。书本和电视交互性都较差，多媒体计算机配有键盘和鼠标供用户输入，这使PC机成为当今主要的交互式多媒体计算机。
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The Definition of Computer Network
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There are many definitions of what the computer networks are. The definitions starting with phrase of the system of linked computers are misled because you could make a network without the linked computers. This network is characterized by people running back and forth between computers with floppy disks in their hands. Under this network, the computers are not linked physically but they still communicate data each other. Therefore, I would like to define it as follows: the computer network is the communication of data from one computer to one or more computers by any means such as people, wires, cables, or a telecommunications system.
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In the early 1980s, personal computer was developed with the concept of independent operation. With personal computer on your desktop, you could enter the information yourself, manipulate it, and produce the report you really wanted. While personal computer had become more powerful and applications for the computers included simple spreadsheet, databases, and word processors, the market for the computers exploded. So, many hardware and software venders joined in the market and it resulted competition.
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The competition pressed intense technological development, which led to increased power on the desktop and lower prices. Desktop computers were soon outperforming older, slower mainframe. Small businesses in particular were able to benefit from information managementservices that, a few years earlier, had been available only to wealthy corporations.
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For all its speed and power, the desktop computing environment had a difficulty in communicating among the users as computing information had became large and complicated. However, business information is useful only when it is communicated between human beings. The obvious solution was to link the desktop computers together. So, the idea of a Local Area Network (LAN) was developed.
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A local area network (LAN) is the communication of a number of computers by cable connecting to each one in a single location, usually a single floor of a building or all the computers in a small company. LANs may be contrasted with wide area networks (WANs). Stated simply, WANs are the communication between LANs by telephone lines leased from the various telephone companies, satellite links, packet radio, or microwave transceivers. The Internet has emerged as both the largest and the least expensive WAN in the world. Many companies take advantage of it now by forming private WANs, known as VPNs, or Virtual Private Networks, through encrypted communications over the Internet.
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对于计算机网络是什么有许多定义。因为没有连接的计算机你也可以建立一个网络，所以用连接的计算机的系统一词来定义会产生误解。这种网络可以被描述为手中拿着软盘的人们在计算机之间跑来跑去传递信息。在这种网络中，计算机之间物理上没有连接，但是它们仍然能够相互传递数据。因此，我喜欢这样定义网络：计算机网络就是可以通过任何一种方式，如人、导线、电缆或通信系统，在一台计算机与另一台或多台计算机之间进行数据通信。
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20世纪80年代初，个人计算机是依据独立操作的思想而开发的。通过桌面上的个人计算机，你可以自己输入信息、操纵它，并且生成你真正想要的报告。当个人计算机变得功能更强，并且计算机的应用开始包括简单的电子表格、数据库和字处理软件时，计算机市场开始蓬勃发展。因此，许多硬件和软件商加入到计算机市场中，从而导致了竞争。
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竞争压力导致了技术的迅猛发展，从而导致了台式机功能的增强和价格的降低。台式机很快战胜了老式的、速度慢的大型机。特别是小型企业能够从信息管理服务中获益，而这种服务在几年前，只有有实力的公司才能获得。
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限于台式机的速度和功能，当计算信息变得大而复杂的时候，台式机计算环境在用户之间进行通信方面遇到了困难。然而，只有当商业信息在人们之间相互传递时，它才能起作用。一种显而易见的解决方法就是将多台台式机连接在一起。于是，局域网的思想就形成了。
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一个局域网（LAN）实现在某个单一区域中（通常是某个建筑物中的一层或者是一家小型公司的全部计算机）通过电缆彼此连接的多台计算机之间的数据通信。局域网可以与广域网（WAN）形成对比。简单地说，广域网就是通过从各电话公司租用的电话线、卫星链路、分组无线网以及微波收发装置，在各局域网之间进行通信。Internet已经成为世界上最大、最便宜的广域网。许多公司现在利用Internet构成被称为"虚拟专用网"（VPN）的专用广域网，在Internet上进行加密通信。
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WHAT DOES NETWORK ADMINISTRATOR DO
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Network administrator has full rights and permissions to all resources on a network. The administrator is usually responsible for installing, managing, and controlling servers and networking components. Administrators can also modify the properties of user accounts and the membership of groups, create and manage printers, install printers, share resources and assign permissions to those resources. Database administrator is responsible for programming and maintaining a large multi-relational database in a networked environment and facilitating direct access to the database by individuals on the network. Workgroup manager is responsible for solving problems, implementing standards and solutions, reviewing performance, and facilitating the efficiency of a specific group of individuals who are connected to larger network environment. Support staff is responsible for providing technical assistance to the system administrator in large complex network environments, and providing routine problem-solving and spot training to end-users. Maintenance contractor is responsible for hardware repairs and upgrades. Webmaster is responsible for implementing and maintaining the content and style of the company's Internet site, keeping the information accurate, up-to-date, and interesting.
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The development of network technology is continuous up to present. The benefits of computer network are as follows:
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. Sharing information the computer can help you centralize the information and maintain control over it if you select one computer to store the shared information and have all other computers reference the information on that computer over the network. . Sharing hardware resources a network allows anyone connected to the network to use printers, fax/modem, scanners, tape backup units or almost any other device that can be attached to a computer.
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. Sharing software resources administrator can centrally install and configure the software and also restrict access to the software. It is easier than doing it on every one of the computers in an organization.
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. Preserving information a network also allows for information to be backed up to a central location. It is difficult to maintain regular backups on a number of stand-alone computers so important information can be lost easily by mistake or by accident.
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. Protecting information a network provides a more secure environment for a company's important information than stand-alone computers. Networks provide an additional layer of security by way of passwords.
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. Electronic-mail (E-mail) the computer network can also help people communicate by E-mail. You can attach electronic documents to mail message like photo, sound and video clip.
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网络管理员对一个网络上的所有资源拥有完全占有权和许可权。网络管理员通常负责安装、管理和控制服务器和网络组件。网络管理员还可以修改用户账号的属性、工作组的成员资格，创建、管理、安装打印机，共享资源以及为那些资源分配权限。数据库管理员负责在一个网络环境中编程和维护一个大型的多关系型数据库，并且为个人在网络上直接访问数据库提供便利。工作组管理员负责解决问题、实现标准和解决方案、检查性能以及提高连接到一个更大的网络环境的特定的一组人员的效率。维护人员负责为在大型复杂的网络环境中工作的系统管理员提供技术帮助，为终端用户提供常规问题解答和现场培训。维修承包商负责对硬件的维修和升级。Web站点管理员负责实现和维护公司Internet站点的内容和风格，保证网站信息正确、及时、有趣。
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至今，网络技术仍然在继续发展。计算机网络的优越性如下。
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. 共享信息。如果你选择一台计算机存储要共享的信息，并且使其他的所有计算机能够通过网络访问这些信息，那么这台计算机就能帮助你集中管理信息和对它进行维护控制。
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. 共享硬件资源。一个网络允许任何一位连接到这个网络的用户使用打印机、传真、调制解调器、扫描仪、磁带备份设备或者几乎所有能够连接到计算机上的其他设备。
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. 共享软件资源。系统管理员能够集中安装和配置软件，还可以限制对软件的访问。这比在一个机构中的每台计算机上都做这些事情要容易得多。
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. 保存信息。一个网络还允许将信息备份到一个集中的位置上。在大量的单独的计算机上维护常规备份是很困难的，因此重要信息很容易因错误或意外而丢失。
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. 保护信息。一个网络比单机可以为一个公司的重要信息提供更加安全的环境。通过密码网络提供了一个附加的安全层。
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. 电子邮件（E-mail）。计算机网络还能通过电子邮件来帮助人们进行通信。可以将诸如相片、声音和视频剪辑等电子文档附加在邮件信息上。
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