指针的应用无处不在。
外部访问私有成员变量，关键要清楚类对象内存的分布情况，用之慎之。
#include <stdio.h>
class Ctest
{
public:
Ctest():i(0){}
void print(){printf("i = %d\n",i);}
private:
int i;
};
int main(void)
{
Ctest test;
test.print();
int *p = (int *)&test;
printf("*p = %d\n",*p);
*p = 10;
test.print();
printf("*p = %d\n",*p);
return 0;
}