1、实验总结3030 数据表示 1.1 实验概述 本实验的目的是更好地熟悉和掌握计算机中整数和浮点数的二进制编码表示。实验中,你需要解开一系列编程“难题”使用有限类型和数量的运算操作实现一组给定功能的函数,在此过程中你将加深对数据二进制编码表示的了解。实验语言:c; 实验环境: linux1.2 实验内容 需要完成 bits.c 中下列函数功能,具体分为三大类:位操作、补码运算和浮点数操作。1.3 实验设计 源码如下:/* * lsbZero - set 0 to the least significant bit of x * Example: lsbZero(0x87654321) = 0x8
2、7654320 * Legal ops: ! & | + * Max ops: 5 * Rating: 1 */int lsbZero(int x) /x右移一位再左移一位实现把最低有效位置0 x = x1; x = x return x; * byteNot - bit-inversion to byte n from word x * Bytes numbered from 0 (LSB) to 3 (MSB) * Examples: getByteNot(0x12345678,1) = 0x1234A978 6 2int byteNot(int x, int n) /x第n个字节每位都和
3、1异或实现取反 int y = 0xff; n = n3; y = y x = x&(0xff); y = y& return !(xy); * logicalAnd - x & y 3 int logicalAnd(int x, int y) /把x和y分别转化为逻辑的0和1,再相与 x = (!(!x)&y); * logicalOr - x | yint logicalOr(int x, int y) /把x和y分别转化为逻辑的0和1,再相或x)|(! * rotateLeft - Rotate x to the left by n * Can assume that 0 = n = 3
4、1 rotateLeft(0x87654321,4) = 0x76543218 25int rotateLeft(int x, int n) /先构造低n位为1,高(32-n)位为0的数z,x左移n位后的数加上x右移(32-n)位的数&z即可 int z; z = (131)(32+(n+1)&z)+(x/* * parityCheck - returns 1 if x contains an odd number of 1s parityCheck(5) = 0, parityCheck(7) = 1 4int parityCheck(int x) /每次将数的低半数位与高半数位比较,再把y
5、右移31位,最后把y转化为逻辑的0和1 int y; y = x16; y = yx; y = y(y31)&0x1)(x30)&0x1); return m0x1; * mult3div2 - multiplies by 3/2 rounding toward 0, * Should exactly duplicate effect of C expression (x*3/2), * including overflow behavior. mult3div2(11) = 16 * mult3div2(-9) = -13 * mult3div2(1073741824) = -5368709
6、12(overflow) 12int mult3div2(int x) /左移一位再+x即x*3,右移一位的时候,当y的最高位和最低位都为0时还要+1 int y = (x1)+(y1)&(y int n = (y x = (mn)&(m(x+(y+1) return (!x); * absVal - absolute value of x absVal(-1) = 1. * You may assume -TMax = x x = (y&(x+1)+(y)& * float_abs - Return bit-level equivalent of absolute value of f fo
7、r * floating point argument f. * Both the argument and result are passed as unsigned ints, but * they are to be interpreted as the bit-level representations of * single-precision floating point values. * When argument is NaN, return argument. Any integer/unsigned operations incl. |, &. also if, whileunsigned float_abs(unsigned uf) int x=uf&(10x7f800000) return uf; else return x; * float_f2i - Return bit-level equi
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