计算机专业英语（第二版）孙建忠电子教案 Chapter3.ppt

Computer English Chapter 3 Binary System and Boolean Algebra 3 实数(Real numbers) xy x is greater than y x≥y x is greater than or equal to y x y x is less than y x?y x is less than or equal to y 0x1 zero is less than x is less than 1 0?x?1 zero is less than or equal to x is less than or equal to 1 |x| mod x / modulus x x2 x squared / x (raised) to the power 2 x3 x cubed x4 x to the fourth / x to the power four xn x to the nth / x to the power n x-n x to the (power) minus n 数学公式的读法(Pronunciation of mathematical expressions) * * Key points:  useful terms and definitions of Binary system and Boolean AlgebraDifficult points:  Conversion of the Binary Systems and Boolean Algebra Requirements: Concepts of Number System and their conversion 2. Boolean Algebra 3. Moore’s Law 4. 科技英语中数学公式的读法 New Words Expressions: decimal system 十进制 abaci n. 算盘 verbal representation 口头表达式 radix n. 根, 基数 quinary system 五进制 duodecimal system 十二进制 stop at 停在 lie in 在于 in fact 事实上 in order to 为了 Roman-number n. 罗马数字 pencil-and-paper 纸和笔的 regardless of a.不管, 不顾 contraction n. 收缩，缩写式，紧缩 gross n. 罗，为一计数单位，1罗=12打 positional notation n. 位置记数法 3.1 The Decimal System Our present system of numbers has 10 separate symbols 0, 1, 2, 3,…, 9, wich are called Arabic numerals. We would be forced to stop at 9 or to invent more symbols if it were not for the use of positional notation. An example of earlier types of notation can be found in Roman numeral, which are essentially additive: III=I+I+I, XXV=X+X+V. New symbols (X, C, M, etc.) were used as the numbers increased in value. Thus V rather than IIIII=5. The only importance of position in Roman numerals lies in whether a symbol precedes or follows another symbol (IV=4 and VI=6). 我们当前的数字系统有0、1、2、3….9十个单独的符号，称之为阿拉伯数字。如果不使用位置符号，我们数到9就被迫停下来，或发明更多的符号。在罗马数字里可以找到早期符号类型的例子，他们基本上是加法的：Ⅲ=Ⅰ+Ⅰ+Ⅰ，XXV=X+X+V。当数值增加时采用新符号（X、C、M等）。这样V就不是IIIII=５。罗马数字中位的唯一重要性在于这个符号处于另一个符号之前或之后（Ⅳ=4和Ⅵ=6）。 3.1 The Decimal System T