【正文】 a process control system， the puter must be capable of sensing the important process variables from the operation and providing the necessary responses to maintain effective control over the process. 。 In a data processing system, this munication is acplished by various input/output devices such as card readers， printers， and CRT consoles. 在數(shù)據(jù)處理系統(tǒng)中，這種交流是通過輸入 /輸出設(shè)備例如讀卡器、打印機(jī)、 CRT 控制板等完成的。為了便于計算機(jī)編程，對人來說相對容易學(xué)習(xí)的高級語言出現(xiàn)了。 Also, different machines use different machine languages. 同時，不同的機(jī)器使用不同的機(jī)器語言。 The sequence of these binarycoded instructions defines the set of calculations and data manipulations by which the puter executes the program. 這些二進(jìn)制編碼的順序限定了計算機(jī)執(zhí)行程序的運算組和數(shù)據(jù)運算 The binarycoded instructions that puters can understand are called machine language. Unfortunately， binarycoded instructions and data are very difficult for human programmers to read or write. 這些計算機(jī)所能識別的二進(jìn)制編碼叫做機(jī)器語言。 The number of bits in the register establishes the word length with which the puter is capable of handling. The number of bits per word can be as few as 4 ( early microputers ) or as many as 64 ( large scientific puters ). Computer Programming Languages 存儲器的位數(shù)代表了電腦能夠處理的字長，每個字所占位數(shù)最少到 4 個（早期微型計算機(jī)）最多到 64 個（大型科學(xué)計算機(jī)） The binary number system could be used to represent any decimal number, alphabetic letter, or other mon symbol. 二進(jìn)制數(shù)能夠用來表示十進(jìn)制數(shù)、字母，或者其他一般符號。 Computer registers are small memory devices that can receive， hold, and transfer data. Each register consists of binary cells to hold bits of 、保存和傳送數(shù)據(jù)的小存儲設(shè)備。 The logic section can also be used to alter the sequence in which instructions are executed when certain conditions are indicated and to perform other functions, such as editing and masking data for arithmetic operations. 當(dāng)指出某些條件時邏輯器能夠改變程序執(zhí)行的順序，也能夠完成其他功能，例如為運算操作編輯和屏蔽數(shù)據(jù)。 The arithmeticlogic unit performs operations such as addition, subtractions, and parisons. These operations are carried out on data in binary form. 運算器完成像加、減和比較的功能。 It sends data to the ALU and tells the ALU what functions to perform on the data and where to store the results. 它將數(shù)據(jù)發(fā)送給運算器并告知運算器數(shù)據(jù)所要求的處理操作和結(jié)果的存儲位置。Arithmeticlogic unit (ALU) 控制器、運算器 The control unit coordinates the various operations specified by the program instructions. 控制器控制由程序制定的各種操作。 Central Processing Unit (CPU) 中央處理器 The central processing unit (CPU) regulates the operation of all system ponents and performs the arithmetic and logical operations on the data. 中央處理器控制所有系統(tǒng)組成的操作并進(jìn)行數(shù)據(jù)的算術(shù)和邏輯運算。 This form of representation is called the binary system. 這種表示形式叫做二進(jìn)制計數(shù)法。 Regardless of the application, the puter executes the program through its ability to manipulate data and numbers in their most elementary form. 不考慮這些應(yīng)用，電腦能自動執(zhí)行程序并以最基本的形式完成數(shù)字和數(shù)據(jù)的運算。 Because the contents of the puter39。軟件將使用者所要求系統(tǒng)完成的各項功能分配給計算機(jī)。 The puter may also be connected to external storage units (e. g， tapes, disks, etc) through the UO section of the puter 電腦也可以通過輸入 /輸出設(shè)備與外圍存儲設(shè)備（比如磁帶、磁盤）鏈接。存儲器完成電腦的記憶功能。 The arithmeticlogic unit carries out the arithmetic and logic manipulations of data. 運算器完成數(shù)據(jù)的算術(shù)和邏輯運算。 a control unit and an arithmeticlogic unit (ALU). 這三個組成部分的關(guān)系如圖 所示，中央處理器通常被認(rèn)為包含兩部分 :一個控制器和一個運算器 .The control unit coordinates the operations of all the other ponents. 控制器控制所有其他組成部分的運輸。機(jī)械工程英語第二版第二部分翻譯 Unit 1 Introduction 前言 The central and essential ingredient of GAD/CAM is the digital puter.〔 1〕 Its inherent speed and storage capacity have made it possible to achieve the advances in image processing, realtime process control, and a multitude of other important functions that are simply too plex and timeconsuming to perform manually. To understand CAD/CAM it is important to be familiar with the concepts and technology of the digital puter CAD/CAM 的重要組成部分是數(shù)字計算機(jī)，它固有的速度以及存儲能力似的它能夠在圖像處 理，實時過程控制以及很多因太復(fù)雜太費時而人工無法完成的其他重要功能方面獲得進(jìn)步，要想懂得 CAD/CAM，熟悉數(shù)字電腦的概念和技術(shù)是很重要的 . The modern digital puter is an electronic machine that can perform mathematical and logical calculations and data processing functions in accordance with a predetermined program of instructions. The puter itself is referred to as hardware, whereas the various programs are referred to as software. 現(xiàn)在數(shù)字計算機(jī)是一部能夠根據(jù)預(yù)定的程序來完成數(shù)字和邏輯運算以及數(shù)據(jù)處理功能的電子設(shè)備，計算機(jī)本身稱為硬件，而各種各樣的程序稱為軟件 There are three basic hardware ponents of a generalpurpose digital puter。 一般用途的數(shù)字計算機(jī)由三種基本硬件組成 .Central processing unit (CPU) 微處理器 .Memory 存儲器 .Input/output ( I/0 )section 輸入 /輸出設(shè)備 The relationship of these three ponents is illustrated in Fig. . The central processing unit is often considered to consist of two subsections。 It controls the input and output of information between the puter and the outside world through the I/O section, synchronizes the transference of signals between the various sections of the puter, and mands the other sections in the performance of their /輸出端口控制電腦與外圍設(shè)備之間信息的輸入與輸出、控制電腦各部分間信 號的傳輸，同時也控制其他部分完成各自的功能。 It adds, subtracts, multiplies, divides, and pares numbers according to programmed instructions. The memory of the puter is the storage unit. 它根據(jù)編制的程序完成數(shù)的加、減、乘、除和比較。 The data stored in this section are arranged in the form of words which can be conveniently transferred to the ALU or I/0 section for /輸出設(shè)備傳輸以進(jìn)行處理的字節(jié)形式存儲在該部分中 Finally, the input/output provides the means for the puter to municate with the external world. This munication is acplished through peripheral equipment such as readers, printers, and process interface devices. 最后，輸入 /輸出設(shè)備提供電腦和外部世界的交流手段，這種交流通過像閱讀機(jī)、打印機(jī)和出口設(shè)備等外圍設(shè)備 完成。 . The software consists of the programs and instructions stored in memory and in external storage units. It is the software that assigns the various functions which the user desires the system to acplish to the puter. 軟件由程序和存儲在內(nèi)存與外存中的指令組成。 The usefulness of the puter lies in its ability to execute the instructions quickly and accurately. 電腦的有用性在于它快速準(zhǔn)確地執(zhí)行程序的能力。 s memory can