编程环境Visual Studio 2017
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#include <stdio.h> #include <stdlib.h> #include <string.h> #include <math.h> #include <memory.h> // practice 1 void p15_1(void) { char *pbin = "01001001"; int num = 0; int p_length = strlen(pbin); for (int i = 0; i < p_length; i++) { num = num * 2 + (pbin[i] - '0'); } printf("the number is %d.\n", num); } // practice 2 int binargstr2int(char *pbin) { int num = 0; int p_length = strlen(pbin); for (int i = 0; i < p_length; i++) { num = num * 2 + (pbin[i] - '0'); } return num; } int p15_2(int argc, char **argv) { unsigned int number1 = 0; unsigned int number2 = 0; if (argc != 3) { printf("Usage: binary_string binarg_string\n"); return 0; } number1 = binargstr2int(argv[1]); number2 = binargstr2int(argv[2]); int nega_number1 = ~number1; int nega_number2 = ~number2; // printf没有二进制输出，使用十六进制输出，将就看吧 printf("The negative of %s and %s are %x and %x\n", argv[1], argv[2], nega_number1, nega_number2); int and = number1 & number2; printf("%s & %s = %x\n", argv[1], argv[2], and); int or = number1 | number2; printf("%s | %s = %x\n", argv[1], argv[2], or); int xor = number1 ^ number2; printf("%s ^ %s = %x\n", argv[1], argv[2], xor); return 0; } // practice 3 int check_open_bit(int num) { int open = 0; while (num != 0) { if ((num & 0x01) == 1) { open++; } num = num >> 1; } return open; } void p15_3(void) { int num = check_open_bit(0x55); printf("0x55 has %d open bits.\n", num); } // practice 4 int check_bit(int number, int bit) { return (number & (0x01 << (bit - 1))); } void p15_4(void) { int num = check_bit(0x55, 1); int num2 = check_bit(0x55, 2); printf("0x55 bit 1 is %d, bit 2 is %d.\n", num, num2); } // practice 5 unsigned int rotate_l(unsigned int number, unsigned int ro) { unsigned int tmp = 0; unsigned int int_bit = sizeof(unsigned int) * 8; for (size_t i = 0; i < ro; i++) { if (((number >> (int_bit -1)) & 0x01) == 1) { number = (number << 1) + 0x01; } else { number = number << 1; } } return number; } void p15_5(void) { unsigned int number = rotate_l(0x80000001, 1); printf("Number:%d", (unsigned int)number); } // practice 6 struct characteristic { unsigned char ch_id; unsigned char ch_size : 7; unsigned char ch_align : 2; unsigned char ch_bold : 1; unsigned char ch_italic : 1; // 看运行示例，貌似还有个加下划线的设置 unsigned char ch_underline : 1; }; void p15_6(void) { // 下面这个想测试看看这个结构体多大，大家可以先分析下，再执行这个代码 int characteristic_size = sizeof(struct characteristic); printf("struct characteristic size = %d\n", characteristic_size); char align[10] = "left"; char choice = 0; struct characteristic chr = { 1, 12, 0, 0, 0, 0 }; while (1) { printf("ID SIZE ALIGNMENT%4s%4s%4s\n", "B", "I", "U"); if (chr.ch_align == 0) { strcpy(align, "left"); } else if (chr.ch_align == 1) { strcpy(align, "center"); } else if (chr.ch_align == 2) { strcpy(align, "right"); } printf("%2d%5d%8s%7s%4s%4s\n", chr.ch_id, chr.ch_size, align, (chr.ch_bold ? "on" : "off"), (chr.ch_italic ? "on" : "off"), (chr.ch_underline ? "on" : "off")); printf("%-20s%-20s%-20s\n", "f)change font", "s)change size", "a)change alignment"); printf("%-20s%-20s%-20s\n", "b)toggle bold", "i)toggle italic", "u)toggle underline"); printf("%-20s\n", "q)quit"); scanf("%c", &choice); while (getchar() != '\n'); if (choice == 'q') { break; } switch (choice) { case 'f': printf("Enter font id(0-255): "); int font_id = 0; scanf("%d", &font_id); chr.ch_id = font_id; while (getchar() != '\n'); break; case 's': printf("Enter font size(0-127): "); int font_size = 0; // 位域地址不能用scanf直接读取，晕 //scanf("%d", &chr.ch_size); scanf("%d", &font_size); while (getchar() != '\n'); chr.ch_size = font_size; break; case 'a': printf("Select alignment:"); printf("%-10s%-10s%-10s\n", "l)left", "c)center", "r)right"); char choice = 0; scanf("%c", &choice); while (getchar() != '\n'); switch (choice) { case 'l': chr.ch_align = 0; break; case 'c': chr.ch_align = 1; break; case 'r': chr.ch_align = 2; break; default: printf("Input error! Nothing have been changed!\n"); break; } break; case 'b': chr.ch_bold = ~chr.ch_bold; break; case 'i': chr.ch_italic = ~chr.ch_italic; break; case 'u': chr.ch_underline = ~chr.ch_underline; break; default: printf("Error choice. Nothing have been changed!\n"); break; } } printf("Done.\n"); return; } // practice 7 void p15_7(void) { /* practice 6中通过sizeof测出来的大小是3字节，所以其实使用int行就足够的了 这里按要求使用unsigned long bit:0 表示下划线开关位 bit:1 表示斜体开关位 bit:2 表示加粗开关位 bit:3-4 表示对齐 bit:8-15 表示字体大小 bit:16-23 表示字体ID */ unsigned long ch = 0; char align[10] = "left"; char choice = 0; while (1) { printf("ID SIZE ALIGNMENT%4s%4s%4s\n", "B", "I", "U"); if ((ch >> 3 & 0x3) == 0) { strcpy(align, "left"); } else if (((ch >> 3) & 0x3) == 1) { strcpy(align, "center"); } else if (((ch >> 3) & 0x3) == 2) { strcpy(align, "right"); } printf("%2d%5d%8s%7s%4s%4s\n", ((ch >> 16) & 0xff), ((ch >> 8) & 0xff), align, (((ch >> 2) & 0x01) ? "on" : "off"), (((ch >> 1) & 0x01) ? "on" : "off"), ((ch & 0x01) ? "on" : "off")); printf("%-20s%-20s%-20s\n", "f)change font", "s)change size", "a)change alignment"); printf("%-20s%-20s%-20s\n", "b)toggle bold", "i)toggle italic", "u)toggle underline"); printf("%-20s\n", "q)quit"); scanf("%c", &choice); while (getchar() != '\n'); if (choice == 'q') { break; } switch (choice) { case 'f': printf("Enter font id(0-255): "); unsigned char font_id = 0; scanf("%d", &font_id); ch &= ~(0xff << 16); ch |= (font_id << 16); while (getchar() != '\n'); break; case 's': printf("Enter font size(0-127): "); unsigned char font_size = 0; scanf("%d", &font_size); while (getchar() != '\n'); ch &= ~(0xff << 8); ch |= (font_size << 8); break; case 'a': printf("Select alignment:"); printf("%-10s%-10s%-10s\n", "l)left", "c)center", "r)right"); char choice = 0; scanf("%c", &choice); while (getchar() != '\n'); // 先将对齐字段清零 ch &= ~(0x03 << 3); switch (choice) { case 'l': ch |= (0x00 << 3); break; case 'c': ch |= (0x01 << 3); break; case 'r': ch |= (0x02 << 3); break; default: printf("Input error! Nothing have been changed!\n"); break; } break; case 'b': if (ch & (0x01 << 2)) { ch &= ~(0x01 << 2); } else { ch |= (0x01 << 2); } break; case 'i': if (ch & (0x01 << 1)) { ch &= ~(0x01 << 1); } else { ch |= (0x01 << 1); } break; case 'u': if (ch & 0x01) { ch &= ~(0x01); } else { ch |= 0x01; } break; default: printf("Error choice. Nothing have been changed!\n"); break; } } printf("Done.\n"); return; } int main(int argc, char **argv) { p15_7(); // p15_2(argc, argv); while (getchar()); return 0; } |
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请问下第一题的
num = num * 2 + (pbin[i] - '0');
是怎么个思路？
num*2相当于左移一位，后面半段就是计算对应位的值
想问下第五题 if ((number & (0x01 << int_bit)) == 1)语句我总觉得是 if ((number & (0x01 << （int_bit-1)) == 1)，这样才能把1移至最高位，求解释谢谢
这一题确实有问题，源码已修改，谢谢！