(1)在没有 p = NULL 时，指针p是指向一个内存地址的，只是这个内存地址对当前程序是非法的。对黑客来说，这可是一个机会。 每次程序崩溃时几乎都会在同一个地址（p所指的位置），这个地址会很容易到黑客手上的，然后黑客可以在指定的内存地址上事先布置好自己的代码，然后运行程序，崩溃时就会到黑客指定的代码上去，结果不堪设想啦。

(2)在有 p = NULL 时，程序同样崩溃，但崩溃的地址是0. 0地址对任何程序都是非法的，所以再牛的黑客也不能把自己的代码布置到内存地址是0的空间上。所以对这种情况，黑客也只能面对崩溃 翻白眼，感叹生不逢时啊。

-(1) there is no　p = NULL　 , the pointer p is pointing to a memory address, only the memory address of the current program is illegal. This is an opportunity for hackers. Every time program crashes are almost in the same address referred to in (p), it will be easy to this address to hackers, hackers can then on the specified memory address prior to decorate your code, and then run the program, the collapse will be to the hacker specify code, the result is unimaginable. (2) in　p = NULL　 Collapse, the program also collapse, but the address is 0. 0 address for any application is illegal, so cattle hackers cannot again to decorate your own code to the memory address space is 0. So in this case, the hacker can only face their collapse, lamented fate ah.