sizeof：（含位域）结构体内存对齐，压缩存储

注：没有额外声明的结果均是在VC++环境中测试得到的结果。
1. sizeof 给出其操作数存储字节大小。
cout << " sizeof: " << endl;
cout << "char = " << sizeof(char) << endl; //1
cout << "short int = " << sizeof(short int) << endl; //2
cout << "unsigned short = " << sizeof(unsigned short) << endl; //2
cout << "int = " << sizeof(int) <