C/C++中unsigned char和char的区别

代码：

 #include <cstdio>
 #include <iostream>

 using namespace std;

 int main(){

     unsigned char c1 = 0x80;
     char c2 = 0x80;
     int a1 = c1;
     int a2 = c2;
     cout<<a1<<endl<<a2<<endl;

     return ;
 }

输出：

128
-128

分析：

由输出可知，unsigned char向int转换时不会扩展最高位，而char（signed char）则会。