1.无符号整形输出

#include
     
      int main(){    unsigned int a=0xffffffff;    printf("%u\n",a);}
     

不能用%d输出。

#include
     
       void main(){    unsigned int a = 0xAAAAAAA7;    unsigned char i = (unsigned char)a;    char* b = (char*)&a;    unsigned char* c = (unsigned char*)&a;    //char 1个字节 unsigned char 1个字节    printf("%d %d\n",sizeof(char),sizeof(unsigned char));    printf("%d %d %d %d\n",sizeof(unsigned int),sizeof(unsigned char),sizeof(char *),sizeof(unsigned char *));    printf("% 8x, % 8x, % 3x,% 8x\n", a, i, *b, *c);}
     

输出： 1 14 1 4 4aaaaaaa7,       a7, ffffffa7,      a7

b或者c是指向a的内存，但是只是指向a的低字节内存。也就是0xA7。b是char*类型，所以把0xA7解释为负数，所以*b输出结果为0xffffffa7，等于-89。而c，为unsigned char*类型，*c的输出为167。