1  // $./a.out
 2  // sizeof(char)                  ===>1 byte
 3  // sizeof(unsigned char)         ===>1 byte
 4  // sizeof(int)                   ===>4 byte
 5  // sizeof(unsigned int)          ===>4 byte
 6  // sizeof(unsigned)              ===>4 byte
 7  // sizeof(short int)             ===>2 byte
 8  // sizeof(short)                 ===>2 byte
 9  // sizeof(unsigned short)        ===>2 byte
10  // sizeof(unsigned short int)    ===>2 byte
11  // sizeof(long int)              ===>4 byte
12  // sizeof(long)                  ===>4 byte
13  // sizeof(unsigned long int)     ===>4 byte
14  // sizeof(unsigned long)         ===>4 byte
15  //
16  // -------------浮点数的机器码由尾数和阶码组合而成，尾数是一个有符号数--------------
17  // sizeof(float)                 ===>4 byte
18  // sizeof(double)                ===>8 byte
19  // sizeof(long double)           ===>12 byte

 1     /*
 2      * printf格式控制字符串中转义字符序列\r练习
 3      * */
 4
 5     #include <stdio.h>
 6
 7     int main()
 8     {
 9         long int integer = 0;
10
11         for (integer = 1; integer <= 987654321l; integer++)
12             if (integer % 4 )
13                 printf(".");
14             else
15                 printf("\r");
16
17         return 0;
18     }  

 1     /*
 2      * printf练习
 3      * 转义字符序列
 4      * */
 5
 6     #include <stdio.h>
 7     int main()
 8     {
 9         printf("\"\"\n");//输出引号
10         printf("\\\n");//输出反斜杠
11         printf("%%\n");//输出百分号
12         printf("\a");//输出一个蜂鸣声
13         printf("abc\rxyz\n");//输出abc后退回再输出xyz
14         /*printf("\c\n");//编译会出warning，提示有无法识别的转义字符序列.进一步如果忽略warning，那么\c整体被忽略(也就是说\c根本就没有被编译入机器码)*/
15
16         printf("%x\n", '%');
17         printf("\x5\n");//格式控制字符串中可以用转义字符序列来实现通用的字符表达方式，通过使用转义字符序列代表任意字符
18
19         return 0;
20     }  

 1     /*
 2      *
 3      * scanf练习
 4      * */
 5
 6     #include <stdio.h>
 7
 8     int main()
 9     {
10
11         int integer = 0;
12         scanf("%d", &integer);
13         printf("%d\n", integer);
14
15         /*
16         int num = 0;
17         scanf("%d", num);//这样的调用scanf()会引起编译warning
18                         //当gcc 02scanf.c -Wall编译时，编译器报warning
19                         //如果忽略warning，所生成目标代码执行时候可能引发操作系统强制终止代码执行， 因为代码执行至scanf("%d", num)时，将num当一个地址值使用，这样可能会引起地址越界
20         printf("%d\n", num);
21         */
22
23         return 0;
24     }  

 1     /*
 2      * 打印C各数据类型当前占有的存储空间大小(byte)
 3      * */
 4
 5     #include <stdio.h>
 6     int main()
 7     {
 8         printf("int->%d\n", sizeof(int));
 9         printf("unsigned int->%d\n", sizeof(unsigned int));
10         printf("unsigned->%d\n", sizeof(unsigned));
11         printf("short int->%d\n", sizeof(short int));
12         printf("short->%d\n", sizeof(short));
13         printf("unsigned short int->%d\n", sizeof(unsigned short int));
14         printf("unsigned short->%d\n", sizeof(unsigned short));
15         printf("long int->%d\n", sizeof(long int));
16         printf("long->%d\n", sizeof(long));
17         printf("unsigned long int->%d\n", sizeof(unsigned long int));
18         printf("unsigned long->%d\n", sizeof(unsigned long));
19         printf("char->%d\n", sizeof(char));
20         printf("unsigned char->%d\n", sizeof(unsigned char));
21         printf("float->%d\n", sizeof(float));
22         printf("double->%d\n", sizeof(double));
23         printf("long double->%d\n", sizeof(long double));
24
25         return 0;
26     }  

 1     /*
 2      * sizeof()练习
 3      * */
 4     #include <stdio.h>
 5
 6     main()
 7     {
 8         char character = 0;
 9         unsigned char character_u = 0;
10         printf("char类型变量character占有%d个字节\n", sizeof(character));
11         printf("unsigned char类型变量character_u占有%d个字节\n", sizeof(character_u));
12
13         /*C语言中我们之所以区分数据类型，就是因为不同数据所占存储空间大小不一*/
14         printf("char类型变量占有%d个字节\n", sizeof(char));
15         printf("unsigned char类型变量占有%d个字节\n", sizeof(unsigned char));
16     }  

 1     /*
 2      * sizeof()练习
 3      * sizeof()只是用来计算操作数占有的存储空间，它不影响操作数本身.请分析本例
 4      * */
 5     #include <stdio.h>
 6
 7     main()
 8     {
 9         char character = 0;
10
11         character = 'a';
12         printf("char类型变量character存放着%c, 占有%d个字节\n",character, sizeof(char));
13
14         sizeof(character = 'b');//sizeof关键字可以对表达式的结果计算占有存储空间大小，但是表达式中的所有修改都不会保留，所以本例程的两行打印结果一样。
15         printf("char类型变量character存放着%c, 占有%d个字节\n",character, sizeof(char));
16     }  

 1     /*
 2      *
 3      * Discreption:计算87+97演示溢出的例程
 4      * 当采用一个字节存储时，87+97会溢出
 5      * */
 6     #include <stdio.h>
 7     main()
 8     {
 9         char c = 87;
10         printf("%d\n", c);
11         c = c + 87;//这里会溢出
12         printf("%d\n", c);
13     }  

 1     /*
 2      * 操作符练习
 3      * */
 4
 5     #include <stdio.h>
 6     main()
 7     {
 8         int num1 = 0, num2 = 0;
 9
10         printf("15 / 7 = %d\n", 15 / 7);
11         printf("15 %% 7 = %d\n", 15 % 7);
12         num1 = num2 = 7;
13         printf("num1是%d, num2是%d\n", num1, num2);
14         num1 += 2;//num = num + 2;
15         printf("num1是%d\n", num1);
16         num1 *= 2 + 3;//复合赋值操作符的优先级和赋值操作符的优先级一样,所以语句num *= 2 + 3;等效于语句num = num * (2 + 3);
17         printf("num1是%d\n", num1);
18
19     }