Pointer learning diary (II)

Declaring a pointer does not automatically allocate any memory ！ Before performing indirect access to the pointer , The pointer must be initialized ;
Or make it point to the existing memory , Or dynamically allocate memory to him

It is illegal to perform an indirect access operation on an uninitialized pointer variable , And such errors are difficult to detect , It is often an irrelevant value ” innocent “ Be modified , This kind of error is difficult to find through debugging ！

NILL A pointer is a pointer that doesn't point to anything . It can be assigned to a pointer , Used to indicate that the pointer does not point to any value .
！！！ Yes NULL The consequences of indirect access operations performed by pointers vary from compiler to compiler （vs2019 The result is to terminate the program , The most important thing is that it won't report errors , Instead, it gets stuck directly during operation ）

It is strongly recommended here because there is no detailed introduction c&c++ The brother of pointer textbook goes to see 《C And a pointer 》
If you are a big man, you can even go to see the pure English version .