字符常量包含多个字符的一点思考--有疑问

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一。先写段程序来看下机器的大端小端

1 #include<stdio.h>

2 /*函数checkCPU判断计算机是使用大端存储还是小端*/

3 int checkCPU()

4 {

5 union w{

6 int a;

7 char b;

8 }c;

9 c.a = 1;

11 return(c.b == 1); //如果是小端的话，则程序返回1

12 }

14 int main()

15 {

16 int b = checkCPU();

17 if(1 == b)

18 {

19 printf("Little Endian!/n"); //小端

20 }

21 else

22 {

23 printf("Big Endian! /n");

24 }

25 return 0;

26 }

编译：gcc testEndian.c -o testEndian

执行结果：

Little Endian!

二。当一个字符常量包含多个字符赋值给一个char类型变量

说明：在第一部分已经测试了机器是使用小端存储，就是高位存储在高地址，地位存储在低地址

1 #include<stdio.h>

3 int main()

4 {

5 char ch;

7 ch = '123'; //编译时候有警告warning: multi-character character constant ;warning: overflow in implicit constant conversion

8 printf("the char ch is %c /n" ,ch); //输出是3，因为是小端字节序;

10 ch = 'abc'; //编译时候有警告

11 printf("the char ch is %c /n" ,ch);

13 return 0;

14 }

编译：gcc testChar1.c -o testChar1

执行结果：

the char ch is 3

the char ch is c

三。一个字符常量包含多个字符，直接打印输出 --不明白？

1 #include<stdio.h>
  2
  3 int main()
  4 {
  5 char *pt = '12'; //编译有警告：initialization makes pointer from integer without a cast
                                  //注意：这里不是char *pt = "12";
  6 printf("the bits of the CPU is %d bits/n/n" ,sizeof(pt) * 8);
  7 printf("the adress of pt is %p /n" ,pt);
  8 printf("the content of 'printf(" " ,'12');'is 0x %x:/n/n" ,'12'); //warning: multi-character character constant
  9 // printf("%d" ,*pt); //为什么会有段错误呢？？
10
11 char *ps = '56';   //可以理解成把'56'对应的ASCII码对应的十六进制当成地址赋值给指针变量ps??
12 printf("the adress of ps is %p /n" ,ps);
13 printf("the content of 'printf(" " ,'56');'is 0x%x :/n/n" ,'56');
14
15 char *pp = '98765'; //warning:character constant too long for its type ,
16 printf("the address of ps is %p /n" ,pp);
17 printf("the content of 'printf(" " ,'98765');'is 0x%x :/n" ,'98765');//warning: character constant too long for its type

18
19 return 0;
20 }

编译：
beanu@beanu-laptop:~/work/day10.22$ gcc testChar.c
testChar.c:5:13: warning: multi-character character constant
testChar.c: In function ‘main’:
testChar.c:5: warning: initialization makes pointer from integer without a cast
testChar.c:8:61: warning: multi-character character constant
testChar.c:11:13: warning: multi-character character constant
testChar.c:11: warning: initialization makes pointer from integer without a cast
testChar.c:13:61: warning: multi-character character constant
testChar.c:15:13: warning: character constant too long for its type
testChar.c:15: warning: initialization makes pointer from integer without a cast
testChar.c:17:62: warning: character constant too long for its type

执行结果：
the bits of the CPU is 32 bits

the adress of pt is 0x3132
the content of 'printf( ,'12');'is 0x 3132:

the adress of ps is 0x3536
the content of 'printf( ,'56');'is 0x3536 :

the address of ps is 0x38373635
the content of 'printf( ,'98765');'is 0x38373635 :
----

个人拙见：printf("%x" , '12'); 是打印出来这个地址对应的十六进制数