小端、大端字节序

小端字节序：将低序字节存储在内存低地址                        
大端字节序：将高序字节存储在内存低地址                        
                                           
16进制可以直观反映内存存储数据的情况                        
                                           
小端字节序存储示例：                                 
int a = 123456789 = 0x075BCD15；            
二进制为：00000111 01011011 11001101 00010101   
内存存储方式： 10101000 10110011 11011010 11100000
                                           
0-->0000                                   
7-->0111                                   
5-->0101                                   
B-->1011                                   
C-->1100                                   
D-->1101                                   
1-->0001                                   
5-->0101                                   
16进制数中的每一位对应4个比特位                

          

//输出主机字节序程序
#include <QDebug>
int main(int argc, char *argv[])
{
    union{
        short s;
        char c[sizeof (short)];
    }un;
    un.s = 0x0102;
    if(sizeof (short) == 2)
    {
        if(un.c[0] == 1 && un.c[2] == 2)
            qDebug() << "big-endian\n";
        else if(un.c[0] == 2 && un.c[1] == 1)
            qDebug() << "little-endian\n";
        else
            qDebug() << ("unknown\n");
    }
    else
       qDebug()<<"sizeof(short) = %d\n"<< sizeof (short);

    return 0;
}