计算机专业英语教程5课件

1、五、借用词借用词一般来自厂商名、商标名、产品代号名、发明者名、地名等，它通过将普通公共英语词汇演变成专业词意而实现。有的则是将原来已经有的词汇赋予新的含义。例如：woofer 低音喇叭tweeter 高音喇叭flag标志、状态cache 高速缓存semaphore 信号量firewall 防火墙mailbomb 邮件炸弹scratch pad 高速缓存fitfall 专用程序入口在现代科技英语中借用了大量的公共英语词汇、日常生活中的常用词汇，而且，以西方特有的幽默和结构讲述科技内容。这时，读者必须在努力扩大自己专业词汇的同时，也要掌握和丰富自己的生活词汇，并在阅读和翻译时正确采用适当的含义。

2、Computer English Chapter 3 Number Systems and Boolean AlgebraKey points: useful terms and definitions of Number system and Boolean AlgbraDifficult points: Conversion of the Number Systems and Boolean AlgbraRequirements:1. Concepts of Number System and their conversion 2. Boolean Algebra 3. Moores La

3、w 4. 科技英语中数学公式的读法 New Words & Expressions:hexadecimal adj.十六进制的; n.十六进制 radix n.根, 基数octal adj.八进制的; n.八进制alphabet n.字母表fractional adj.分数的, 小数的whole number n.整数remainder n.余数significant figure n.有效数字quotient n.商algorithm n.算法complement n. 补码，余角carry n.进位 3.1 Number Systems Abbreviations: Binary-code

4、d hexadecimal (BCH) 二进制编码的十六进制The use of the microprocessor requires a working knowledge of binary, decimal, and hexadecimal numbering systems. This section provides a background for those who are unfamiliar with number systems. Conversions between decimal and binary, decimal and hexadecimal, and bi

5、nary and hexadecimal are described.3.1 Number Systems 使用微处理器需要掌握二进制、十进制和十六进制数制系统的基本知识，本节为那些不熟悉数制系统的读者提供这方面的背景知识。说明了十进制与二进制之间、十进制与十六进制之间，及二进制与十六进制之间的转换。Before numbers are converted from one number base to another, the digits of a number system must be understood. Early in our education, we learned th

6、at a decimal, or base 10, number was constructed with 10 digits: 0 through 9. The first digit in any numbering system is always a zero. For example, a base 8 (octal) number contains 8 digits: 0 through 7; a base 2 (binary) number contains 2 digits: 0 and 1. 3.1.1 Digits 将数从种数制向另一种数制转换之前，必须了解数的计数系统。在

7、早期教育中，我们已学习了十进制数，或以10为基的数，它由10个数字组成：0到9。任何计数制的第一个数字总是零，这种规则适用于任何其他数制。例如，以8为基的数(八进制)包含8个数字：0到7，而以2为基的数(二进制)包含2个数字：0和 l。The exponential powers of the positions are critical for understanding numbers in other numbering systems. The position to the left of the radix (number base) point, called a decimal

8、 point only in the decimal system, is always the units position in any number system. For example, the position to the left of the binary point is always 20 or 1; the position to the left of the octal point is 80 or 1. In any case, any number raised to its zero power is always 1, or the units positi

9、on.3.1.2 Positional Notation 位的指数幂在理解其他计数制中的数时是个关键。基数小数点，在十进制中称为十进制小数点，其左边的位在任何数制中都是个位。例如，二进制小数点左边的位是20或1。而八进制小数点左边的位是80或1。在任何情况下，任何数的零次幂总是1，或1个单位。The position to the left of the units position is always the number base raised to the first power; in a decimal system, this is l01, or l0. In a binary

10、system, it is 21, or 2; and in an octal system it is 81, or 8. Therefore, an 11 decimal has a different value from an 11 binary. The 1l decimal is composed of 1 ten plus 1 unit and has a value of 11 units; while the binary number 11 is composed of 1 two plus 1 unit, for a value of 3 decimal units. T

11、he 11 octal has a value of 9 units.3.1.2 Positional Notation 个位左边的位总是基数的1次幂，在十进制系统中是101，或10；在二进制中是21，或2；而在八进制中是81，或8。因此，十进制的11与二进制的11具有不同的数值。十进制11表示个10加上一个1，其值为11；二进制11表示个2加上个1，其值为3；八进制11的值为9。In the decimal system, positions to the right of the decimal point have negative powers. The first digit to

12、the right of the decimal point has a value of 10-1, or 0.1. In the binary system, the first digit to the right of the binary point has a value of 2-1, or 0.5. In general, the principles that apply to decimal numbers also apply to numbers in any other number system.3.1.2 Positional Notation 在十进制系统中，对

13、于十进制小数点右边的位，它的幂为负数。十进制小数点右边第一位数的值为10-1，或0.1。在二进制中,二进制小数点右边第位数的值为2-1或0.5。一般来说，十进制使用的计数法可以用于任何其他数制。Hexadecimal numbers are often used with computers. A 6A.CH (H for hexadecimal) is illustrated with its weights in Example 3-3. The sum of its digits is 106.75, or 106. The whole number part is represente

14、d with 616 plus 10 (A)1. The fraction part is 12 (C) as a numerator and 16 (16-1) as the denominator, or 12/16, which is reduced to 3/4.3.1.3 Conversion to Decimal 计算机经常使用十六进制。例3-2给出了一个十六进制数6A.CH(H表示十六进制)，以及它的权。它的各位数值之和是106.75，即106。整数部分用616加10(A) 1表示；分数部分用12(C)作为分子，16作为分母(16-1)，或表示为12/16，化简得3/4。 Con

15、versions from decimal to other number systems are more difficult to accomplish than conversion to decimal. To convert the whole number portion of a number to decimal, divide by the radix. To convert the fractional portion, multiply by the radix. 3.1.4 Conversion From Decimal 由十进制转换成其他进制比由其他进制转换成十进制困

16、难。转换十进制整数部分时，要用基数去除，转换分数部分时，要用基数去乘它们。Whole Number Conversion from Decimal. To convert a decimal whole number to another number system, divide by the radix and save the remainders as significant digits of the result. An algorithm for this conversion as is follows: 1. Divide the decimal number by the

17、radix (number base). 2. Save the remainder (first remainder is the least significant digit), 3. Repeat steps 1 and 2 until the quotient is zero.3.1.4 Conversion From Decimal 转换十进制整数部分 将十进制整数转换成其他数制时，要用基数去除，并且保存余数，作为结果的有效数字。这种转换的算法如下：1. 用基数除十进制数。2. 保存余数(最先得到的余数是最低有效位数字)。3. 重复步骤l和2，直到商为零。Converting fr

18、om a Decimal Fraction. Conversion from decimal fraction to another number base is accomplished with multiplication by the radix. For example, to convert a decimal fraction into binary, multiply by 2. After the multiplication, the whole number portion of the result is saved as a significant digit of

19、the result, and the fractional remainder is again multiplied by the radix. When the fraction remainder is zero, multiplication ends. Note that some numbers are never-ending. That is, a zero is never a remainder. An algorithm for conversion from a decimal fraction is as follows3.1.4 Conversion From D

20、ecimal 转换十进制小数部分 转换10进制小数部分是用基数乘来完成的。例如，要将十进制 小数转换成二进制，要用2乘。乘法之后，乘积的整数部分保存起来作为结果的一个有效位，剩余的小数再用基数2去乘。当剩余的小数部分为0时，乘法结束。有些数可能永远不会结束，即余数总不为0。转换十进制小数部分的算法如下：At times, data are stored in complement form to represent negative numbers. There are two systems that are used to represent negative data: radix an

21、d radix -1 complements. The earliest system was the radix -1 complement, in which each digit of the number is subtracted from the radix -1 to generate the radix -1 complement to represent a negative number. 3.1.6 Complements 有时，数据以补码的形式存储，以便表示负数。有两种表示负数的方式：补码和反码(基数减l的补)，最早的方式是反码。为了得到负数的反码表示，用基数-1减去该

22、数的每一个数位上的数字。Example 3-9 shows how the 8-bit binary number 01001100 is ones (radix -1) complemented to represent it as a negative value. Notice that each digit of the number is subtracted from one to generate the radix -1 (ones) complement. In this example, the negative of 01001100 is 10110011. The s

23、ame technique can be applied to any number system, as illustrated in Example 3-10, in which the fifteens (radix -l) complement of a 5CD hexadecimal is computed by subtracting each digit from a fifteen.3.1.6 Complements 例3-9表示了如何将8位二进制数01001100对l取补(基数减1的补)，以便表示成个负数。注意，用1减去该数的每一位数字，以便生成反码。在此例中，0100110

24、0的负数是10110011。同样的技术可适用于任何数制。如例3-10所示，十六进制数5CD的反码是从15(基-1)中减去它的每一位数字得到的。 Today, the radix -1 complement is not used by itself; it is used as a step for finding the radix complement. The radix complement is used to represent negative numbers in modern computer systems. (The radix -1 complement was use

25、d in the early days of computer technology.) The main problem with the radix -1 complement is that a negative or a positive zero exists; in the radix complement system, only a positive zero can exist. 3.1.6 Complements 如今，反码已不单独使用，而作为求补码的一个步骤使用，补码是当代计算机系统表示负数的方法(反码用于早期的计算技术中)。反码的主要问题是它存在负零或者正零，而补码系统

26、中只能存在正零。To form the radix complement, first find the radix -1 complement, and then add a one to the result. Example 3-11 shows how the number 0100 1000 is converted to a negative value by twos (radix) complementing it. 3.1.6 Complements 为得到补码，先求反码，然后将1加到结果上。例3-11表示了如何通过对2(基为2)取补的方式，将数01001000转换成负数。T

27、o prove that a 0100 1000 is the inverse (negative) of a 1011 0111, add the two together to form an 8-digit result. The ninth digit is dropped and the result is zero because a 0l00100 is a positive 72, while a 1011 0111 is a negative 72. The same technique applied to any number system. Example 3-12 s

28、hows how the inverse of a 345 hexadecimal is found by first fifteens complementing the number, and then by adding one to the result to form the sixteens complement. As before, if the original 3-digit number 345 is added to the inverse of CBB, the result is a 3-digit 000. As before, the fourth bit (c

29、arry) is dropped. This proves that 345 is the inverse of CBB. 3.1.6 Complements 为验证0100 1000是1011 1000的反(负数)，将两者相加得到一个8位结果。去掉第9位数字，结果是零。因为0100 1000是正数72，而1011 0111是负数72。同样的枝术可用于任何数制。例3-12表示如何求十六进制数345的负数，首先求该数15的补，然后将1加到结果上，得到16的补，同前面类似，如把原来的3位数345加上其负数CBB，则结果是3位000，第4位(进位)被丢掉。这证明了345是CBB的反。The conc

30、ept of a Boolean algebra was first proposed by the English mathematician George Boole in 1847. Since that time, Booles original conception has been extensively developed and refined by algebraists and logicians. The relationships among Boolean algebra, set algebra, logic, and binary arithmetic have

31、given Boolean algebras a central role in the development of electronic digital computers. 3.2 Boolean Algebra 布尔代数的概念最初是由英国数学家George Boole于1847年提出来的，从那时起，代数学家和逻辑学家们更广泛地发展了Boole最初的概念，并使之更加精练。由于布尔代数、集合代数、逻辑学和二进制算术之间的内在联系，使得布尔代数的理论在电子计算机的发展中起到举足轻重的作用。The most intuitive development of Boolean algebras a

32、rises from the concept of a set algebra. Let S=a, b, c and T=a, b, c, d, e be two sets consisting of three and five elements, respectively. We say that S is a subset of T, since every element of S (namely, a, b, and c) belongs to T. Since T has five elements, there are 25 subsets of T, for we may choose any individual element to be included or omitted from a subset. Note that these 32 subsets include T itself and the empty set, which contains no elements at all. If T contains all elements of concern, it is called the universal set. Given