专业英语翻译

专业英语翻译 The development of the microcomputer during the 1970s brought about a revolution in engineering design .The industrial revolution at the turn of the nineteenth century heralded the development of machines which replaced physical drudgery by the mechanical means .Apart from a few exceptions, however, these machines required manual supervision because the problem of controlling this mechanical power was not at all straightforward. Many types of automatics control systems have appeared during the twentieth century, based on electronic, mechanical, hydraulic and fluidic principles. In each case the design techniques have been similar because each component of the system usually contributes a single well defined function to the system behaviors. The microcomputer represents a fundamentally different approach to the design of a system .Its physical form is quite simple and reliable, consisting of a few general-purpose elements which can be programmed to make the specific system function as required. It is the controlling program that be designed to give the system the required behavior, and it contain “components” and “subassemblies” just like any other kind of engineering .The program, or software, is just of the engineered system as the physical hardware, but it is much less susceptible to failure, provided that it is designed properly. The idea of programmed system is not new; electronic computers have been in existence for many decades. However, it has taken the development of the large scale integrated circuit—the silicon chip—to produce computers which are cheap, rugged, and reliable enough to be incorporated into engineering designs as components. The techniques of software design are well known to computer scientists and it is not surprising that the principles of good engineering design and “software engineering” are essentially those of good engineering design .We shall see that engineering design using software allows systems to be designed more easily than using more conventional techniques. It is the combination of developments in electronic device technology with those in computer technology which has enabled the microcomputer to be produced, and these technologies have “converged” to produce the micro-electronic industry which we see today. From Computer to Microcomputer The development of electronic technology has been the basis of the development of the computer, although the earliest computer antedates electronics by many decades. In fact the choice of candidate for “first computer” depends very much upon what we choose to regard as a computer; for example one calculating aid, the abacus, has been known since antiquity. Blaise Pascal invented the first real calculating machine in 1642; this machine was a purely mechanical device consisting of a set of geared wheels arranged so that a complete revolution of any wheel rotated the wheel immediately to its left through one-tenth of a revolution. In the first half of the nineteenth century Babbage designed programmable calculation “engines” suing mechanical techniques, although computers as we know them today were impractical because the precision engineering is required to construct them. The twentieth century saw the arrival of the electromechanical computers, which were developed for some special military tasks such as code-breaking and gun-aiming. However, these lacked speed and they were soon superseded by full electronic designs using thermionic valves. After the Second World War the computer was developed for civilian use as a large and expensive arithmetic-performing machine for business and scientific purpose. The power consumption and unreliability of valves limited the use of computers until valves were ousted by the introduction of the transistor, and new information storage techniques appeared which allowed smaller and more powerful computers to be produced. The 1960s saw the introduction of the minicomputer which was small and cheap enough at a few thousands of pounds—or dollars—to be produced in relatively large numbers for the industrial control and the laboratory instrumentation purposes. The minicomputer became yet cheaper when integrated circuits were introduced. As these circuits became more complex the number of integrated circuits required to construct a functioning computer fell, until simple minicomputers made significant reductions to be made in the time needed to design, develop, and commission the projects requiring large amount of the electronic logic. More recent developments in integrated circuit technology have led to the introduction of microcomputers, small computers fabricated using relatively few integrated circuit components. In fact an entire microcomputer can be made as a single chip. At the heart of any computer is a Central Processing Unit or CPU, and the corresponding heart of the microcomputer is the microprocessor or MPU (Micro-Processor Unit), which is simply a CPU implemented on a silicon chip. Its processing power is higher than that of its giant predecessors and yet it is cheap and robust enough to be treated as simply another engineering component. The microcomputer was conceived as a device which could be programmed in a very flexible fashion to give almost any desired behavior by means of a list of electronic instructions. Using a microcomputer involves programming skill in producing these lists of instructions as more conventional electronic and mechanical design techniques. As its name suggests, the microcomputer is organized in much the same way as a conventional computer; indeed, it may be regarded as the “natural” outcome of the “evolution” of the computer from its earliest days. The Advantages and Disadvantages of Microcomputer Systems The first advantage has already been mentioned; the large-scale integration of electronic systems has reduced the number if components which are used, leading to an increase in the overall reliability of the system and a reduction in assembly costs. The decrease in size which results from large-scale integration means that the equipment based on microcomputers is usually much smaller, lighter, and more robust than that using older technologies. Microcomputers can be made in large quantities because they are general purpose devices, and this leads to a much lower unit cost when compared with more conventional methods of producing systems with similar complexity. This standardization can be extended to the printed circuits on which the integrated circuits are mounted, and very sophisticated microcomputer systems can be purchased as single printed circuit boards at quite reasonable cost. The use of standard components also offers the possibility of standard test fixtures for use in fault diagnosis. It is the program which defines the function of a microcomputer based system and usually it is in this program that most of the system design is carried out. Many concepts which are similar to the engineers are found in software engineering, such as the requirement for modular design and for testability and maintainability. In fact, the presence of a microcomputer in a system can ease the problem of fault finding if the possibility of such faults has been anticipated by the designer, since the microcomputer may be used to provide diagnose of the precise nature of the fault. However, time dependent faults are less easily detected, and may become apparent only when the equipment has been operating for many hours. The microcomputer might appear at this point to have been presented as something of an engineer‟s panacea, but unfortunately there are also some disadvantages which arise from using a microcomputer. The first is mainly of interest in purely electronic system; microcomputer logic is slower than hardwired electronic logic by a factor of perhaps 100. In many applications, for example those which have mechanical interfaces, this is not important because the speed of response is limited by external factors rather than the speed of the microcomputer itself. The problem of fault finding in a malfunctioning microcomputer system is more serious. The fault could be in the electronic hardware, or it might be due to a programming error, and faults which involve interactions between hardware and software are especially inscrutable. Conventional fault-finding techniques and instruments such as oscilloscopes are frequently useless in such cases. But fortunately some methods for locating and identifying faults have been developed. System using microcomputers Electronic systems are used for handling information in the most general sense; this information may be the telephone conversation, the instrument reading or the company‟s accounts, but In each case the same main types of operation are involved: the processing, the storage and the transmission of information. In conventional electronic design, these operations are combined at the function level: for example, a counter, whether electronic or mechanical, storages the current count and increments in by one as required. A system such as an electronic clock which employs counters has its storage and processing capabilities spread throughout the system because each counter is able to storage and process numbers. Present day microprocessor based systems depart from this conventional approach by separating the three functions of processing, storage, and transmission into different sections of system. This partitioning into three main functions was devised by Von Neumann during the 1940s, and was not conceived especially for microcomputers. Almost every computer ever made has been designed with this structure, and despite the enormous range in their physical forms, they have all been of essentially the same basic design. In a microprocessor based system the processing will be performed in the microprocessor itself. The storage will be by means of memory circuits and the communication of information into and out of the system will be by means of special input/output (I/O) circuits. It would be impossible to identify a particular piece of hardware which performs the counting in a microprocessor based clock because the time would be stored in the memory and incremented at regular intervals by the microprocessor. However the software which defined the system‟s behavior would contain sections that perform as counters. The apparently rather abstract approach to the architecture of the microprocessor and its associated circuits allows it to be very flexible in use, since the system is defined almost entirely in the software. The design process is largely one of software engineering, and the similar problems of construction and maintenance which occur in conventional engineering are encountered when producing software. Microcomputers use RAM (Random Access Memory), into which data can be written and from which data can be read again when needed. This data can be read back from the memory in any sequence desired, and not necessarily the same order in which it was written, hence the expression „random‟ access memory. Another type of memory ROM (Read Only Memory) is used to hold fixed patterns of information which cannot be affected by the microprocessor; these patterns are not lost when power is removed and are normally used to hold the program which defines the behavior of a microprocessor based system. ROMs can be read like RAMs, but unlike RAMs they cannot be used to store variable information. Some ROMs have their data patterns put in during manufacture, while others are programmable by the user by means of special equipment and are called programmable ROMs. The widely used programmable ROMs are erasable by means of special ultraviolet lamps and are referred to as EPROMs, short for Erasable Programmable Read Only Memories. Other new types of device can be erased electrically without the need for ultraviolet light, which are called Electrically Erasable Programmable Read Only Memories, EEPROMs The microprocessor processes data under the control of the program, controlling the flow of information to and from memory and input/output devices. Some input/output devices are general-purpose types while others are designed for controlling special hardware such as disc drives or controlling information transmission to other computers. Most types of I/O devices are programmable to some extent, allowing different modes of operation, while some actually contain special-purpose microprocessors to permit quite complex operations to be carried out without directly involving the main microprocessor. The microprocessor, the memory and the input/output circuit may all be contained on the same integrated circuit provided that the application does not require too much program or data storage. This is usually the case in low-cost application such as the controllers used in the microwave ovens and the automatic washing machines. The use of single package allows considerable cost savings to be made when articles are manufactured in large quantities. As technology develops, more and more powerful processors and larger and larger amounts of memory are being incorporated into single chip microcomputers with resulting saving in assembly costs in the final products. For the foreseeable future, however, it will continue to be necessary to interconnect a number of integrated circuits to make a microcomputer whenever larger amounts of storage or input/output are required. Another major engineering application of microcomputers is in process control. Here the presence of the microcomputer is usually more apparent to the user because provision is normally made for programming the microcomputer for the particular application. In process control applications the benefits of fitting the entire system on to a single chip are usually outweighed by the high design cost involved, because this sort of equipment is produced in smaller quantities. Moreover, process controllers are usually more complicated so that it is more difficult to make them as single integrated circuits. Two approaches are possible; the controller can be implemented as a general-purpose microcomputer rather like a more robust version of a hobby computer, or as a „packaged‟ system, designed for replacing controllers based on older technologies such as electromagnetic relays. In the former case the system would probably be programmed in conventional programming language might be used, for example one which allowed the function of the controller to be described in terms of relay interconnections. In either case, the programs can be stored in RAM, which allows them to be altered to suit changes in application, but this makes the overall system vulnerable to loss of power unless batteries are used to ensure continuity of supply. Alternatively the programs can be stored in ROM, in which case they virtually become part of the electronic „hardware‟ and are often referred to as firmware. More sophisticated process controllers require minicomputers for their implementation, although the use of large scale integrated circuits „blurs‟ the distinction between mini- and microcomputers. Products and process controllers of various kinds represent the majority of present-day microcomputer applications, the exact figures depending on one‟s interpretation of the word „product‟. Virtually all engineering and scientific uses of microcomputers can be assigned to one or other of these categories. 20世纪70年代的微型计算机发展引起了工程设计的一场革命。在19世纪之 初的工业革命宣布了用机械工具代替繁重的体力劳动的机器有了进展。但除了少 数例外，这些机器需要人的操作监管，这是因为控制这种机械动力的问题并不都 是简明的。 在20世纪，出现了许多种基于电子、机械、液压和流体原理的自动控制系统。 由于系统中的每一元件通常对系统的运转状态只起单一的确定的功能，各种类型 系统的设计技术是相似的。 微型计算机代表了一种根本不同的系统设计方法。其物理形式是非常简单可 靠的，包括一些通用元件，通过编程取得所需的系统功能。控制程序的设计必须 给予系统所需的功能作用，它应像其他工程类一样包含“元件”和“组件”。程 序或软件，如同物理硬件形成的工程系统，但如果设计正确（得法），是不易出 问题的。 可编程系统的设想并非新鲜，电子计算机已使用几十年。但是，它的应用得 益于大规模集成电路——硅片的发展，从而使生产的计算机变得足够的便宜、耐 用且可靠，能够以部件的形式综合到工程设计中。软件设计技术对计算机科学家 来说已是十分清楚的，而且好的工程设计和“软件工程”是好的工程设计的基本 条件，我们将会看见使用软件的工程设计使系统设计比使用更常规的方法更为简 便。 正是由于电子器件技术的发展和计算机技术发展的综合产生了微型计算机。 这些技术“汇集起来”形成了今天我们看到的微电子产业。 尽管最早的计算机先于电子学好几十年，电子工业的发展使计算机发展的基础。 事实上，对“第一台计算机”的代表的选择主要取决于我们将何种东西看作是计 算机，例如一种辅助工具，算盘，在古代就已被热所知了。 布莱斯?帕斯卡于1642念发明第一台真正的计算机器；这是包含一组齿轮传动轮的纯机械装置，齿轮的布置使得任何一齿轮旋转一周就驱动其紧邻的齿轮 向左旋转十分之一周。在19世纪前半叶，巴贝奇用机械技术设计了可编程计算“机器”，尽管我们今天知道这些计算机是不实用的，因为要建造它们需要很精 细的工程。20世纪出现了电机计算机，开发用于诸如密码破译、枪的瞄准等特 殊的军事任务，但是这些机器速度不高，并迅速使用热离子管的全电子设计所取 代。 二次大战后民用计算机被开发来作为一种商务和科学用途的大型昂贵的执行算 术运算的机器。热离子管的功耗和使用的不可靠限制了计算机的使用，直至晶体 管的出现取代了热离子管，而且新的信息存储技术的采用使得生产的计算机更小 更强大。 20世纪60年代目睹了小型计算机的出现，这种计算机很小并且价格低廉至 几千英镑（或美元），所以以相对较大的数量被生产用于工业控制和试验仪器。 当集成电路被采用时，小型计算机就变得更为便宜。随着这些电路变得更加复杂， 建造功能化计算机所需的集成电路数量则下降，直至可能只用一块或两块印刷电 路板构成小型计算机，这些小型计算机使得在设计、开发和委托加工具有大量电 子逻辑的时，所需的时间大为减少。 集成电路技术的更新发展促使了微型计算机的出现，也就是用相对少量的集 成电路元件构成了小计算机。事实上,一完整的计算机可用一个芯片做出。在任一计算机中，其核心是中央处理器或CPU，而微型计算机的核心是微处理器或MPU，它是用一个硅片制成的CPU。它的处理能力比早先的巨大芯片还要强，并且对仅仅作为另一种工程部件来说，已足够强大。 微型计算机被设想为能以非常灵活的方式进行编程的装置，通过一组电子指 令清单就能给出几乎任何所希望的功效。使用计算机会涉及在生成指令清单时的 编程技巧以及常用的电子和机械设计技术。正如其名字所指示的，微型计算机以 常用计算机十分相同的方法组成；事实上，它可看作是从最早的计算机“进化” 的“自然”结果。 第一个有点已经提到过了，就是电子系统的大规模集成已经降低了所用的 元件数量，促使系统的总体可靠性的提高和装备费用的降低。由于大规模集成引 起的尺寸减小意味着基于微计算机的设备功能通常要小得，轻得多，并且比用旧 技术制成的设备更为强大。 由于微计算机是通用设备，能大量地生产，所以与构成同样复杂性系统的常 规方法相比，会使单位成本低得多。这种标准化可扩大到安装集成电路的印刷电 路，这样就能以相当合理的价格购到用单块印刷电路板形成的非常复杂的微机系 统。而且标准元件的使用使标准测试附件在故障诊断中的应用成为可能。 是程序限定了微机化系统的功能，通常也正是在这个程序环境下，大多数的 系统设计得以开展。在软件工程设计中，工程师会遇到许多熟悉的概念，例如模 块设计的必要性，以及可测试性和维护性设计的必要性。事实上，例如某些系统 错误可被设计者所预见，微机在系统中的存在就使错误查找问题变得容易，这些 因为微机可用来诊断错误的准确性。但是，基于时间的错误是不容易探测的，这 些错误可能要运行许多小时后才会变得清楚。 到此，微机看起来给了工程人员的某些万灵药，但是不幸的是在使用微机时 也会引发某些不利因素。首先是纯电子系统仍具有吸引力；微机逻辑比硬线连接 的电子逻辑大约慢100倍。在许多应用中，例如具有机械接口的场合，这是不重 要的，因为响应速度是由外部因素而不是微机本身速度所限制的。 在不良的微机系统中，错误的查找问题就更加严重。这种错误可能存在于电 子硬件中，或者是由于编程错误，而涉及硬软件交互的错误则特别难以克服。常 用的错误查找技术和仪器，如示波器，常常对它们无能为力，但幸运的是用于错 误定位和辨别的方法已经被开发出来。 广义地说，电子系统是用于处理信息的，这种信息可以是电话交谈、仪器读 书或企业账户，但是各种情况下都涉及相同的主要操作：信息处理、存储和传送。 在常规的电子设计中，这些操作都是以功能平台方式组合起来的，例如记数器， 无论是电子还是机械的，都要存储当前值，并按要求将该值增1。诸如采用记数 器的电子钟之类的任一系统要使其存储和处理能力遍布整个系统，因为每个记数 器都能存储和处理一些数字。 当前微处理器化系统与上述的常规方法不同，它将处理、存储和传输三个功 能分离形成不同的系统单元。这种形成三个主要单元的分离方法是冯?诺伊曼在 20世纪40年代所设想出来的，并且是针对微计算机设想。从此几乎所有制成的 计算机都是用这种结构设计的，尽管包含宽广的物理形式，从根本上来说它们均 是具有相同的基本设计。 在微处理器化系统中，处理是由微处理器本身完成的。存储是利用存储器电 路，而进入和出自系统的信息传输则是利用特定的输入/输出（I/O）电路。要在 一个微处理器化时钟中找出执行计数功能的一个特殊硬件是不可能的，因为时间 存储在存储器中，而在固定的时钟间隔下由微处理器控制增值。但是，规定系统 运转过程的软件包含实现计数器功能的单元。由于系统几乎完全由软件所定义， 所以对微处理器结构和其辅助电路这种看起来非常抽象的处理方法使其在应用 时非常灵活。这种设计过程主要是软件工程，而且在生产软件时，就会遇到产生 于常规工程中相似的构造和维护问题。 微计算机常使用RAM（随机存取存储器），在RAM中数据可被写入，并且在需 要时可被再次读出。这种数据存储器能以任一所希望的次序从存储器中读出，不 必按写入时的相同次序，所以有“随机”存取存储器。另一类型ROM（只读存储器）用来保持不受微处理器影响的固有的信息标本；这些标本在电源切断后不会 丢失，并通常用来保存规定微处理器化系统运转过程的程序。ROM可像RAM一样被读取，但与RAM不一样的是不能用来存储可变的信息。有些ROM在制造时将其数据标本放入，而另外的则可通过特殊的设备由用户编程，所以称为可编程ROM。被广泛使用的可编程ROM可利用特殊紫外线灯擦除，并被称为EPROM，即可擦除可编程只读存储器的缩写。另有新类型的器件不必用紫外线灯而用电擦除，所以 可称为电可擦除可编程只读存储器EEPROM。 微处理器在程序控制下处理数据，并控制流向和来自存储器和输入/输出装置的信息流。有些输入/输出装置是通用型的，而另外一些则是设计来控制如磁 盘驱动器的特殊硬件，或控制传给其他计算机的信息传输。大多数类型的I/O装置在某种程度下可编程，允许不同形式的操作，而有些则包含特殊用途微处理 器的I/O装置不用主微处理器的直接干预，就可实施非常复杂的操作。 假如应用中不需要太多的程序和数据存储量，微处理器、存储器和输入/输出可全被包含在同一集成电路中。这通常是低成本应用情况，例如用于微波炉和 自动洗衣机的控制器。当商品被大量生产时，这种单一芯片的使用就可节省相当 大的成本。当技术进一步发展，更强的处理器和更大数量的存储器被包含成单片 微型计算机，结果使最终产品的装配成本得以节省。但是在可预见的将来，当需 要大量的存储器或输入/输出时。还是有必要继续将许多集成电路相互联结起来， 形成微计算机。 微计算机的另一主要工程应用是在过程控制中。这时，由于装置是按特定的 应用情况有微机编程实现的，对用户来说微计算机在存在通常就更加明显。在过 程控制应用中，由于这种设备以较少的数量生产，将整个系统安装在单个芯片上 所获得的利益常不比所涉及的高设计成本。而且，过程控制器通常更为复杂，所 以要将它们做成单独的集成电路就更为困难。可采用两种处理，将控制器做成一 种通用的微计算机，正像较强版本的业余计算机那样；或者做成“包裹”式系统， 按照像电磁继电器那样的较老式的技术进行设计，来取代控制器。对前一种情况， 系统可以用常规的编程语言来编程，正如以后要介绍的语言那样；而另一种情况， 可采用特殊用途的语言，例如那种使控制器功能按照继电器相互连接的方法进行 描述。两种情况下，程序均能存于RAM，这让程序能按应用情况变化时进行相应 的变化，但是这使得总系统易受掉电影响而工作不正常，除非使用电池保证供电 连续性。另一种选择是将程序存在ROM中，这样它们就变成电子“硬件”的一部 分并常被称为“固件”。 尽管大规模集成电路的应用使小型和微型计算机的差别变得“模糊”，更复 杂的过程控制器需要小型计算机实现它们的过程。各种类型的产品和过程控制器 代表了当今微计算机应用的广泛性，而具体的结构取决于对“产品”一词的解释。 实际上，计算机的所有工程和科学上的应用都能指定来进行这些种类中的某一或 某些工作。