#include <stdio.h>
 
int main()
{
    char t = 0xFF;
    unsigned char u = (unsigned char)t;
    //%d把对应的整数按有符号十进制输出，%u把对应的整数按无符号十进制输出
    printf("t=%d,t2u=%u\n",t,u);
    return 0;//c标准规定建议main函数返回值为int
}