[理学]ch03-Translation.pptVIP

Questions? 用什么来表示十六进制的一位？ 0, 1, …, 9, ??? 如何知道一个数是十六进制数？ X, x, or (N)16 十六进制数的一位可以用多少位二进制数表示？ Questions? 用什么来表示八进制数的一位？ 0, 1, 2, 3, 4, 5, 6, 7 如何知道一个数是八进制数？ 0, o, or (N)8 八进制数的一位可以用多少位二进制数表示？ 取补(complement)？？ 考虑一个时钟， 标准时间为4点整，而有一只表已经7点了，为了校准时间，可以采用两种方法：一是将时针退7-4=3个格；一是将时间往前拨12-3=9个格。 7 - 3 = 4 7 + 9 （mod 12）= 4 将减法转换成加法运算 方法二 1.The number is changed to binary; the sign is ignored 忽略符号，将数转换成二进制。 2.0s are added to the left of the number to make a total of N bits. 不足 N 位时，左侧用0 填充至 N位。 3.If the sign is positive, no more action is needed. If the sign is negative, complement the bits and add 1. 正数时不做任何其他操作；负数时，按位取反后加1。 方法二 正数时不做任何操作；负数时按位取反后加1. Floating-Point representation To convert a floating-point number to binary: 1.Convert the integer part to binary. 将整数部分转换成二进制 2.Convert the fraction to binary. 将小数部分转换成二进制 3.Put a decimal point between the two parts. 在两部分中间加上小数点 Example 11 Interpretin decimal if the number was stored as a one’s complement integer. Solution The leftmost bit is 1, so the number is negative. First complement it . The result is The complement in decimal is 9. So the original number was –9. One’s complement means reversing all bits. If you one’s complement a positive number, you get the corresponding negative number. If you one’s complement a negative number, you get the corresponding positive number. If you one’s complement a number twice, you get the original number. Note: Two’s complement is the most common, the most important, and the most widely used representation of integers today. Note: Two’s Complement Format Ranger: -(2 N-1)~ +(2N-1-1) Table 3.7 Range of two’s complement integers # of Bits --------- 8 16 32 -128 -32,768 -2,147,483,648 0