Level 1 and level 2 pointers in C Language

Level 1 and level 2 pointers in C Language

Pointer Concept

The pointer is the address, which can be used to find the specified data.

The pointer is the address, so when using it, it is often said that the pointer variable is a pointer

The pointer variable is the variable that stores the address.

Int * p1; // a variable is applied for, that is, a memory is opened in the memory to store data.

// Eight bytes are opened, and the pointer occupies 8 bytes in Mac.

The pointer should be used as a pointer variable.

1> arithmetic operations

+ How many bytes does 1 move?

Type: int *, long *, char *

2> get the address data

The pointer stores the address to retrieve the data from the address.

Addressing operator * & p1-> p1

3> modify the data in the address

4> use as function parameters (*****)

If it is not a pointer variable, but a common variable, it is a value transfer: the function is two different variables, but the stored data is the same (like sending a file)

If the pointer variable is passed, that is, the address is passed, then the reference is passed: the function can be regarded as the same variable inside and outside (like sending a link)

Since function parameters can be modified using pointers, which affects the variables outside the function, function parameters are usually set to pointer-type variables.

Functions that return multiple data using parameters

Scanf ("% d", & num );

Level 2 pointer

The second-level pointer is the pointer to the first-level pointer (n-level pointer is the pointer to the n-1-level pointer)

The essence of a pointer is an address, so several levels of pointers are just an address. The only difference is the addressing result (* p)

1> in development, the second-level pointer is used to return a first-level pointer data using a function or method.

2> if you need to use function parameters to return data, if the returned data is normal, pass the first-level pointer

3> If a level-1 pointer is returned, the parameter should be a level-2 pointer.

4> If an n-level pointer is returned, the parameter should be a n + 1-level pointer.

* P1 refers to the num value, * p2 refers to the p1 memory address, and ** p2 also refers to the num value ......