【初探】判斷系統位數及主機字節序

1.判斷64位32位

• 方法一：用sizeof()

#include <stdio.h>
int main(void)
{
    printf("%d\n", sizeof(void *)):
    return 0;
}

• 方法二：不用sizeof()

#include <stdio.h>
#include <stdlib.h>

int main(void)
{
     int **p = NULL;
     p = (int **)malloc(2*16);

     printf("1=%p, 2=%p\n", &p[0], &p[1]);

     return 0;
}

其他不用sizeof的方法見：
http://blog.csdn.net/i_scream_/article/details/51619456

2.判斷主機字節序

#include <stdio.h>

typedef union TEST_U_
{
    short a;
    char b[2];
}TEST;

int main(void)
{
    TEST test;
    test.a = 0x1234;
    if (test.b[0] == 0x12 && test.b[1] == 0x34)
    {
        printf("big\n");
    }
    else if(test.b[0] == 0x34 && test.b[1] == 0x12)
    {
        printf("little\n");
    }
    return 0;
}