C++的学习记录 - 01

动态内存分配和释放一直不怎么明白。

实验程序为：

 1 # include <iostream>
 2 # include <cstdlib>
 3 using namespace std;
 4
 5 int main()
 6 {
 7     int *p;
 8     if((p = new int(5)) == 0)
 9     {
10         cout<<"can‘t allocate more memory, terminating.."<<endl;
11         exit(1);
12     }
13
14     cout<<"Before deleting:"<<endl;
15     cout<<"p = "<<p<<endl;
16     cout<<"*p = "<<*p<<endl<<endl;
17
18     delete p;
19
20     cout<<"After deleting:"<<endl;
21     cout<<"p = "<<p<<endl;
22     cout<<"*p = "<<*p<<endl;
23
24     return 0;
25 }

程序结果为：

Before deleting:
p = 0x9724008
*p = 5

After deleting:
p = 0x9724008
*p = 0

堆内存被释放后，指针还指向原来的位置，内容改变为“0”。

为什么是0呢。。。。。。