復習題1、將下列十進制數轉換為二進制形式：
a. 3
b. 13
c. 59
d. 119
答：
a. 11
b. 1101
c. 111011
d. 1110111
2、將下列二進制值轉換為十進制、八進制和十六進制形式：
a. 00010101
b. 01010101
c. 01001100
d. 10011101
答：
a. 21, 025, 0x15
b. 85, 0125, 0x55
c. 76, 0114, 0x4C
d. 157, 0235, 0x9D
3、計算下列表達式；假設每個值為8位：
a. ~ 3
b. 3 & 6
c. 3 | 6
d. 1 | 6
e. 3 ^ 6
f. 7 >> 1
g. 7 << 2
答：
a. 252
d. 2
c. 7
d. 7
e. 5
f. 3
g. 28
4、計算下列表達式；假設每個值為8位：
a. ~ 0
b. !0
c. 2 & 4
d. 2 && 4
e. 2 | 4
f.2 || 4
g. 5 << 3
答：
a. 255
b. 1
c. 0
d. 1
e. 6
f. 1
g. 40
5、因為ASCII碼僅使用最后的7位，所以有時需要屏蔽掉其他位。相應的二進制掩碼是什么？分別以十進制、八進制和十六進制形式如何表示這個掩碼？
答：掩碼在二進制中為1111111。它的十進制表示為127，八進制表示為0177，十六進制表示為0x7F。
6、在程序清單15.2中，可以做以下替換，把：
while(bits-- > 0)
{
mask |= bitval;
bitval <<= 1;
}
用：
while(bits-- > 0)
{
mask |= bitval;
bitval *= 2;
}
替換，而程序仍將工作。這是否意味著*= 2等同于<<= 1？|=和+=又怎樣？
答：
bitval *= 2和bitval << 1都把bitval的當前值加倍，所以他們是等效的。但是mask += bitval和mask |= bitval只有在bitval和mask沒有同時設置為打開的位時才具有相同的效果。例如，2 | 4 = 6，但是3 | 6 = 7。
7、
a. Tinkerbell計算機有一個硬件字節，可以將該字節讀入程序。該字節包括下列信息：
| 位 | 含義 |
| 0到1 | 1.4MB軟盤驅動器數量 |
| 2 | 未使用 |
| 3到4 | CD-ROM驅動器數量 |
| 5 | 未使用 |
| 6到7 | 硬盤驅動器數量 |
Tinkerbell和IBM PC一樣從右到左填充結構位字段。創建一個適于存放該信息的位字段模板。
b. Klinkerbell與Tinkerbell類似，但它從左到右填充結構。請為Klinkerbell創建相應的位字段模板。
答：
a.
struct tinkerbell {
unsigned int diskdrivers : 2;
unsigned int : 1;
unsigned int cdromdrivers: 2;
unsigned int : 1;
unsigned int harddrivers : 2;
};
b.
struct klinkerbell {
unsigned int harddrivers : 2;
unsigned int : 1;
unsigned int cdromdrivers: 2;
unsigned int : 1;
unsigned int diskdrivers : 2;
};
編程練習1、
#include <stdio.h>
#include <string.h>
#include <math.h>
int stoi(char *);
int main(void)
{
char pbin[9];
printf("請輸入一個(8位)二進制字符串：\n");
puts("在一行開始處鍵入[Enter]結束循環：");
while(fgets(pbin, 9, stdin) != NULL && pbin[0] != '\n')
{
printf("二進制序列%s轉換為十進制數為: %d\n", pbin, stoi(pbin));
while(getchar() != '\n')
continue;
printf("請輸入一個二進制字符串：\n");
}
printf("Bye!\n");
return 0;
}
int stoi(char * s)
{
int len = strlen(s);
unsigned int tot = 0;
for(int i = 0; i < len; i++)
if(s[i] == '1')
tot += pow(2, len - 1 - i);
return tot;
}
看看別人寫的代碼（借鑒h
ttp://ptgmedia.pearsoncmg.com/images/9780321928429/downloads/9780321928429_ProgrammingExerciseAnswers_Selected.pdf）
即優美又考慮周全，要學習?。。?br />
#include <stdio.h>
#include <stdbool.h>
#include <limits.h> // for CHAR_BIT 一個char的位數
#include <string.h>
int bstr_to_dec(const char * str);
bool check_val(const char * str);
char * s_gets(char * st, int n);
int main(void)
{
const size_t SLEN = CHAR_BIT * sizeof(int) + 1;
char value[SLEN];
printf("Enter a binary number with up to %zu digits: ", SLEN - 1);
while(s_gets(value, SLEN) != NULL && value[0] != '\0')
{
if(!check_val(value))
puts("A binary number contains just 0s and 1s.");
else
printf("%s is %d\n", value, bstr_to_dec(value));
puts("Enter next number (empty line to quit): ");
}
puts("Done");
return 0;
}
bool check_val(const char * str)
{
bool valid = true;
while(valid && *str != '\0')
{
if(*str != '0' && *str != '1')
valid = false;
str++;
}
return valid;
}
int bstr_to_dec(const char * str)
{
int val = 0;
while(*str != '\0')
val = 2 * val + (*str++ - '0'); // 二進制——>十進制太神奇了
return val;
}
char * s_gets(char * st, int n)
{
char * ret_val;
char * find;
ret_val = fgets(st, n, stdin);
if(ret_val)
{
find = strchr(ret_val, '\n');
if(find)
*find = '\0';
else
while(getchar() != '\n')
continue;
}
return ret_val;
}
2、
#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <limits.h> // for CHAR_BIT 一個char的位數
#include <string.h>
int bstr_to_dec(const char * str);
char * itobs(int n, char * ps);
void show_bstr(const char * str);
int main(int argc, char *argv[])
{
const size_t SLEN = CHAR_BIT * sizeof(int) + 1;
char bin_str[SLEN];
int value0, value1, value3;
if(argc != 3)
{
printf("輸入格式錯誤!\n");
printf("請按照\"%s 字符串 字符串\"格式輸入\n");
exit(1);
}
value0 = bstr_to_dec(argv[1]);
value1 = bstr_to_dec(argv[2]);
printf("~%s = ", argv[1]);
show_bstr(itobs(~value0, bin_str));
printf("\n~%s = ", argv[2]);
show_bstr(itobs(~value1, bin_str));
value3 = value0 & value1;
printf("\n%s & %s = ", argv[1], argv[2]);
show_bstr(itobs(value3, bin_str));
value3 = value0 | value1;
printf("\n%s | %s = ", argv[1], argv[2]);
show_bstr(itobs(value3, bin_str));
value3 = value0 ^ value1;
printf("\n%s ^ %s = ", argv[1], argv[2]);
show_bstr(itobs(value3, bin_str));
return 0;
}
int bstr_to_dec(const char * str)
{
int val = 0;
while(*str != '\0')
val = 2 * val + (*str++ - '0'); // 二進制——>十進制太神奇了
return val;
}
char * itobs(int n, char * ps)
{
int i;
static int size = CHAR_BIT * sizeof(int);
for(i = size - 1; i >= 0; i--, n >>= 1)
ps[i] = (01 & n) + '0';
ps[size] = '\0';
return ps;
}
/* 4位一組顯示二進制字符串 */
void show_bstr(const char * str)
{
int i = 0;
while(str[i])
{
putchar(str[i]);
if(++i % 4 == 0 && str[i])
putchar(' ');
}
}
運行結果圖：
3、
#include <stdio.h>
#include <limits.h> // for CHAR_BIT 一個char的位數
char * itobs(int n, char * ps);
int get_count(const char *);
int main(void)
{
const size_t SLEN = CHAR_BIT * sizeof(int) + 1;
char bin_str[SLEN];
int number, count;
puts("請輸入一個整數: ");
while(scanf("%d", &number) == 1)
{
count = get_count(itobs(number, bin_str));
printf("%d這個數中打開的位的數量: %d\n", number, count);
puts("請輸入一個整數: ");
}
puts("Bye!");
return 0;
}
char * itobs(int n, char * ps)
{
int i;
static int size = CHAR_BIT * sizeof(int);
for(i = size - 1; i >= 0; i--, n >>= 1)
ps[i] = (01 & n) + '0';
ps[size] = '\0';
return ps;
}
int get_count(const char * ps)
{
int count = 0;
while(*ps != '\0')
if(*ps++ == '1')
count++;
return count;
}
4、
#include <stdio.h>
#include <limits.h> // for CHAR_BIT 一個char的位數
int fun_itobs(int n, int index);
int main(void)
{
int number, count;
puts("請輸入一個整數: ");
while(scanf("%d", &number) == 1)
{
puts("請輸入一個位的位置: ");
while(scanf("%d", &count) != 1 || count < 0 || count > 31)
{
printf("您輸入的不是一個數字，或者范圍不在%d到%d之間\n", 0, CHAR_BIT * sizeof(int) - 1);
printf("請您重新輸入: \n");
while(getchar() != '\n')
continue;
}
if(fun_itobs(number, count))
printf("%d在位%d上的值是1\n", number, count);
else
printf("%d在位%d上的值是0\n", number, count);
puts("請輸入一個整數: ");
}
puts("Bye!");
return 0;
}
int fun_itobs(int n, int index)
{
int i, ret_val;
static int size = CHAR_BIT * sizeof(int);
char ps[size + 1];
for(i = size - 1; i >= 0; i--, n >>= 1)
ps[i] = (01 & n) + '0';
ps[size] = '\0';
if(ps[size - 1 - index] == '1')
ret_val = 1;
else
ret_val = 0;
return ret_val;
}
5、（借鑒http://ptgmedia.pearsoncmg.com/images/9780321928429/downloads/9780321928429_ProgrammingExerciseAnswers_Selected.pdf的做法，因為實在沒想到）
#include <stdio.h>
#include <limits.h> // for CHAR_BIT 一個char的位數
char * itobs(int n, char * ps);
unsigned int rotate_1(unsigned int, unsigned int);
int main(void)
{
char bin_str1[CHAR_BIT * sizeof(int) + 1];
char bin_str2[CHAR_BIT * sizeof(int) + 1];
unsigned int number, count, result;
printf("Enter an integer (q to quit): \n");
while(scanf("%d", &number))
{
printf("Enter the number of bits to be rotated: \n");
if(scanf("%d", &count) != 1)
break;
result = rotate_1(number, count);
itobs(number, bin_str1);
itobs(result, bin_str2);
printf("%u rotated is %u.\n", number, result);
printf("%s rotated is %s.\n", bin_str1, bin_str2);
printf("Enter an integer (q to quit): \n");
}
puts("Bye!");
return 0;
}
char * itobs(int n, char * ps)
{
int i;
const static int size = CHAR_BIT * sizeof(int);
for(i = size - 1; i >= 0; i--, n >>= 1)
ps[i] = (01 & n) + '0';
ps[size] = '\0';
return ps;
}
unsigned int rotate_1(unsigned int n, unsigned int b)
{
static const int size = CHAR_BIT * sizeof(int);
unsigned int overflow;
b %= size;
overflow = n >> (size - b);
return (n << b) | overflow; // 沒想到這點
}
6、（全部是自己寫的，完美實現?。。。?br />
#include <stdio.h>
#include <string.h>
/* 字體是否粗體 */
#define BOLD_ON 1
#define BOLD_OFF 0
/* 字體對齊方式 */
#define LEFT 0
#define RIGHT 1
#define CENTER 2
/* 字體是否斜體 */
#define ITALIC_ON 1
#define ITALIC_OFF 0
/* 字體是否有下劃線 */
#define UNDERLINE_ON 1
#define UNDERLINE_OFF 0
#define MASK 0xFFFFFF00
#define MASK1 0xFFFF80FF
struct font {
unsigned int font_id : 8;
unsigned int font_size : 7;
unsigned int : 1;
unsigned int alignment : 2;
unsigned int bold : 1;
unsigned int italic : 1;
unsigned int underline : 1;
unsigned int : 3;
};
void show(const struct font * ft);
int getlet(const char *);
int getmenu(void);
void eatline(void);
int main(void)
{
/* 初始化font結構 */
struct font ft = {1, 12, LEFT, BOLD_OFF, ITALIC_OFF, UNDERLINE_OFF};
int choice;
int id, size, align;
show(&ft);
putchar('\n');
while((choice = getmenu()) != 'q')
{
switch(choice)
{
case 'f': printf("Enter font id (0-255): ");
while(scanf("%d", &id) != 1 || id < 0 || id > 255)
{
printf("您輸入的不是一個整數，或者范圍不在0到255之間\n");
while(getchar() != '\n');
continue;
printf("Enter font id (0-255): ");
}
eatline();
ft.font_id = (ft.font_id & MASK) | id;
putchar('\n');
show(&ft);
break;
case 's': printf("Enter font size (0-127): ");
while(scanf("%d", &size) != 1 || size < 0 || size > 255)
{
printf("您輸入的不是一個整數，或者范圍不在0到127之間\n");
while(getchar() != '\n');
continue;
printf("Enter font size (0-127): ");
}
eatline();
ft.font_size = ((ft.font_size & MASK1) >> 8) | size;
putchar('\n');
show(&ft);
break;
case 'a': printf("Select alignment: \n");
puts("l) left c) center r)right");
align = getlet("lcr");
switch(align)
{
case 'l': ft.alignment = LEFT;
break;
case 'c': ft.alignment = CENTER;
break;
case 'r': ft.alignment = RIGHT;
break;
}
putchar('\n');
show(&ft);
break;
case 'b': ft.bold = BOLD_ON;
putchar('\n');
show(&ft);
break;
case 'i': ft.italic = ITALIC_ON;
putchar('\n');
show(&ft);
break;
case 'u': ft.underline = UNDERLINE_ON;
putchar('\n');
show(&ft);
break;
}
}
puts("Bye!");
return 0;
}
void show(const struct font * ft)
{
printf("ID\tSIZE\tALIGNMENT\tB\tI\tU\n");
printf("%d\t%d", ft->font_id, ft->font_size);
switch(ft->alignment)
{
case LEFT: printf("%10s", "left");
break;
case RIGHT: printf("%10s", "right");
break;
case CENTER: printf("%10s", "center");
break;
default: printf("unknown alignment");
}
printf("%14s%8s%8s\n", ft->bold == BOLD_OFF? "off" : "on",
ft->italic == ITALIC_OFF? "off" : "on",
ft->underline == UNDERLINE_OFF? "off" : "on");
}
int getlet(const char * s)
{
char c;
c = getchar();
while(strchr(s, c) == NULL)
{
printf("請您在%s這串字符串中輸入一個字符: \n", s);
while(getchar() != '\n')
continue;
c = getchar();
}
while(getchar() != '\n')
continue;
return c;
}
int getmenu(void)
{
int i;
const char * str[7] = {
"change font",
"change size",
"change alignment",
"toggle bold",
"toggle italic",
"toggle underline",
"quit"
};
const char pstr[8] = "fsabiuq";
for(i = 0; i < 7; i++)
{
printf("%c) %s ", pstr[i], str[i]);
if(i % 3 == 2)
putchar('\n');
}
if(i % 3 != 0)
putchar('\n');
return getlet(pstr);
}
void eatline(void)
{
while(getchar() != '\n')
continue;
}
7、（有大問題，明天再看！??！借鑒
http://ptgmedia.pearsoncmg.com/images/9780321928429/downloads/9780321928429_ProgrammingExerciseAnswers_Selected.pdf但是程序也有問題）
#include <stdio.h>
#include <string.h>
#include <ctype.h>
#define LEFT 0x00000
#define CENTER 0x08000
#define RIGHT 0x10000
#define BOLD 0x20000
#define UNDERLINE 0x80000
#define ID_MASK 0xFF
#define SIZE_MASK 0x7F00
#define ALIGN_MASK 0x18000
#define ITALIC 0x40000
#define SIZE_SHIFT 8
typedef unsigned long font;
char do_menu(font * f); // f為一個指向unsigned long的指針
void show_font(font f);
char get_choice(const char *);
void show_menu(void);
void eatline(void);
void get_id(font * f);
void get_size(font * f);
void get_align(font * f);
int main(void)
{
font sample = 1 | (12 << SIZE_SHIFT) | LEFT | ITALIC; // sample = 0100 0000 1100 0000 0001(斜體,沒有預留空隙)
while(do_menu(&sample) != 'q')
continue;
puts("Bye!");
return 0;
}
char do_menu(font * f)
{
char response;
show_font(*f);
show_menu();
response = get_choice("fsabiuq");
switch(response)
{
case 'f': get_id(f); break;
case 's': get_size(f); break;
case 'a': get_align(f); break;
case 'b': *f ^= BOLD; break;
case 'i': *f ^= ITALIC; break;
case 'u': *f ^= UNDERLINE; break;
case 'q': break;
default: printf("menu problem\n");
}
return response;
}
void show_font(font f)
{
printf("\n%4s %4s %9s %3s %3s %3s\n", "ID", "SIZE", "ALIGNMENT", "B", "I", "U");
printf("%4lu %4lu", f & ID_MASK, (f & SIZE_MASK) >> SIZE_SHIFT);
switch(f & ALIGN_MASK)
{
case LEFT: printf("%7s", "left"); break;
case CENTER: printf("%7s", "center"); break;
case RIGHT: printf("%7s", "right"); break;
default: printf("%7s", "known"); break;
}
printf("%8s %3s %3s\n\n", (f & BOLD) == BOLD ? "on" : "off",
(f & ITALIC) == ITALIC ? "on" : "off",
(f & UNDERLINE) == UNDERLINE ? "on" : "off");
}
char get_choice(const char * s)
{
char ch;
ch = getchar();
ch = tolower(ch);
while(strchr(s, ch) == NULL)
{
printf("Please enter one of the following: %s\n", s);
eatline();
ch = tolower(getchar());
}
eatline();
return ch;
}
void eatline(void)
{
while(getchar() != '\n')
continue;
}
void show_menu(void)
{
puts("f) change font s) change size a) change alignment");
puts("b) toggle bold i) toggle italic u) toggle underline");
puts("q) quit");
}
void get_id(font * f)
{
int id;
printf("Enter font id (0-255): ");
scanf("%d", &id);
id = id & ID_MASK;
//*f |= id;
*f = (*f & 0xFFF00) | id; // 相應位要先置為0之后再用|運算符吧！?。。?/span>問題出現在這）
eatline();
}
void get_size(font * f)
{
int size;
printf("Enter font size (0-127): ");
scanf("%d", &size);
*f &= (0xF8011);
*f |= (size << SIZE_SHIFT) & SIZE_MASK;
eatline();
}
void get_align(font * f)
{
printf("Select alignment: \n");
printf("l) left c) center r) right\n");
switch(get_choice("lcr"))
{
case 'l': *f &= ~ALIGN_MASK;
*f |= LEFT;
break;
case 'c': *f &= ~ALIGN_MASK;
*f |= CENTER;
break;
case 'r': *f &= ~ALIGN_MASK;
*f |= RIGHT;
break;
default: printf("alignment problem\n");
}
}