char和short 给int赋值或与int比较时 需要特别注意

#include <stdio.h>

int main()

{

int a;

char c =0x81;

a = c;

printf("%x\n", a); //0xffffff81

}

#include <stdio.h>

int main()

{

int a;

char c =0x81;

a = c & 0xff;

printf("%x\n", a); //0x81

}

#include <stdio.h>

int main()

{

char buf[8];

buf[0] = 1;

buf[1] = 0xf2;

if(buf[0] == 1)

printf("buf0 == 1\n");

if(buf[1] == 0xf2)

printf("buf1 == 0xf2\n");

printf("aa:%x\n", aa); //f2

printf("buf1:%x\n", buf[1]); //fffffff2

}