c程序辨别系统是64位 or 32位

#include
int main(void)
{
        int i = 0x80000000;
        if(i<0){
                printf("i = %d\n", i);
                printf("32 bits.\n");
        }else{
                printf("i = %d\n", i);
                printf("64 bits.\n");
        }

        return 0;
}