1：处理器存储多字节数据时，存在大端和小端模式；
2：处理器存储单字节数据时，位顺序也存在大端和小端模式；
3：小端模式：低地址存储低位的数据（字节），高地址存储高位数据（字节）；
4：大端模式：低地址存储高位数据（字节），高地址存储高位数据（字节）；
One：使用共同体结构判断多字节存数模式
/********************************
*Function:测试处理器大小端模式
*Platform:X86
*Compiler:GCC
*Author:Programme By Golf
** *****************************/
#include <stdio.h>
typedef union
{
unsigned short Data;
struct
{
unsigned char a[2];
}cc;
}Big_Little;
Big_Little big_little;
void main()
{
char *ptr1 = "Little_Mode";
char *ptr2 = "Big_Mode";
big_little.Data = 0x11aa;
if(big_little.cc.a[0] == 0xaa && big_little.cc.a[1] == 0x11)
{
printf("big_little.Data = 0x%x\n",big_little.Data);
printf("addre = %p value = 0x%x\n",&big_little.cc.a[0],big_little.cc.a[0]);
printf("addre = %p value = 0x%x\n",&big_little.cc.a[1],big_little.cc.a[1]);
printf("%s\n",ptr1);
}
if(big_little.cc.a[1] == 0xaa && big_little.cc.a[0] == 0x11)
{
printf("big_little.Data = 0x%x\n",big_little.Data);
printf("addre = %p value = 0x%x\n",&big_little.cc.a[0],big_little.cc.a[0]);
printf("addre = %p value = 0x%x\n",&big_little.cc.a[1],big_little.cc.a[1]);
printf("%s\n",ptr2);
}
}
Two：使用共同体结构判断单字节存数模式（位顺序）
/********************************
* *Function:测试处理器大小端模式
* *Platform:X86
* *Compiler:GCC
* *Author:Programme By Golf
* ** *****************************/
#include <stdio.h>
typedef union
{
unsigned char data;
struct
{
unsigned char a:1;
unsigned char b:1;
unsigned char c:1;
unsigned char d:1;
unsigned char e:1;
unsigned char f:1;
unsigned char g:1;
unsigned char h:1;
}cc;
}big_little;
big_little Big_Little;
void main()
{
Big_Little.data = 0x01;
if(Big_Little.cc.a == 0x01)
printf("Little_MOde\n");
else
if(Big_Little.cc.h == 0x01)
printf("Big_MOde\n");
else
printf("error\n");
}
Three：使用指针判断大小端模式
/******************************
*测试处理器大小端模式
*Platform:X86
*Compiler:GCC
*Author:Programme By Golf
*****************************/
#include <stdio.h>
void main(void)
{
char c1;
char c2;
short *ptr;
*ptr = 0x11aa;
c1 = *((char *)ptr);
c2 = *((char *)ptr+1);
printf("c1_address = %p,c1_value = 0x%x\n",(char *)ptr,(unsigned char)c1);
printf("c2_address = %p,c2_value = 0x%x\n",(char *)ptr+1,c2);
if((unsigned char)c1 == 0xaa)
printf("Little_Endian\n");
if((unsigned char)c1 == 0x11)
printf("Big_Endian\n");
}
以上代码，在ubuntu10.04系统验证通过，X86架构处理器为小端模式；
