The concept of C language pointer

Catalog

One 、 The concept of pointer

Two 、 The four elements of the pointer

3、 ... and 、 Pointers and pointer variables

Four 、 The type of pointer

5、 ... and 、 Pointer arithmetic

1、 Fetch address operator &

2、 Indirect operators *

3、 Pointer set declaration

6、 ... and 、 The function of the pointer

7、 ... and 、 Reference resources   

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One 、 The concept of pointer

To facilitate access to the contents of memory , We give each memory unit a number , This number is called address or pointer .

1. The pointer has directivity , Memory address for storing other variables .
2. The pointer is the address , The address is the pointer . Essentially, it is a nonnegative integer with limited operation
3. A pointer is a data type , So pointers have their own memory , What's stored is the address ( Number ).
4. The pointer is a variable , The variable used to hold the address , There are types .
5. System （32 Bit or 64 position ） All pointer sizes in are the same
6. Pointer and pointer variable are two different concepts
7. A pointer is a variable with a pointer
8. The secondary pointer refers to the space where the primary pointer of the same type is stored ,
9. Multi level analogy. The pointer storage space of the previous level is pointed to as the second level points to the first level  

 

Two 、 The four elements of the pointer

1. The type of the pointer itself Remove the pointer name , The rest is the type of the pointer itself
2. The type pointed to by the pointer Remove the pointer name and a *, The rest is the type pointed to by the pointer
3. The memory of the pointer itself is used to store a number (32 Bit system occupies 4 Bytes ,64 Bit system occupies 8 Bytes ）
4. The memory that the pointer points to It can be all kinds of , Point to the starting address

3、 ... and 、 Pointers and pointer variables

1.    Pointer and pointer variable are two different concepts , But here's the thing , Usually, when we describe, we will abbreviate pointer variables as pointers .
2. The pointer is the address , The address is the pointer , It is a shape unsigned integer , An integer , Its size depends on whether the system is 16 32 still 64 Bit 16/8=2byte 32/8=4byte 64/8=8byte.
3. Pointer variable is actually a variable , Only the content stored is the address , Such as int* p, This p It's the pointer type , Its value is stored in the address .

4. After the pointer is referenced, the value of the variable corresponding to the address is obtained .

5. The secondary pointer is a pointer to the address of the primary pointer

 

1、p Is the name of a pointer variable , Indicates the memory address pointed to by this pointer variable , If you use %p To output , It will be a 16 Hexadecimal number  

2、*p Indicates the contents stored in the memory address pointed to by this pointer , Generally, it is a variable or constant consistent with the pointer type .

3、 & Is the address operator ,&p It's just a pointer p The address of .

&p What is it with p What's the difference? ？

       p and &p The difference is the pointer p It is also a variable , Since it's a variable , The compiler must allocate memory addresses for it , Both ordinary variables and pointer variables have an address in memory , It's like the program defines a int Type variables i, The compiler should allocate a piece of memory space for it sample .

       &p Indicates that the compiler is a variable p Allocated memory address , and p Is a pointer variable , This special identity doomed it to point to another memory address , The programmer makes it point to a memory address according to the needs of the program , The memory address it points to is used p Express . and ,p The content in the address pointed to is used *p Express

Four 、 The type of pointer

1. Basic types ：int 、short、long、float 、double、char, Such as int *p;// Means to define a pointer , This pointer points to the integer variable , This pointer will store the address of the integer variable .
2. Array pointer ：** The pointer points to an array ,int （*a）[10]; // Indicates that the pointer points to a int The length of the type is 10 Array of
3. A function pointer ：** Pointer to a function ,void （*a）（）;// Indicates that the pointer points to a function with no parameters and no return value

5、 ... and 、 Pointer arithmetic

1、 Fetch address operator &

• Format ：& Variable name
• meaning ： Take out the address where the variable is stored
• purpose ： Pass variable values across functions （ Novices can ignore it for the time being ）

2、 Indirect operators *

• Format ：* Pointer name / Address name
• meaning ： Take out the corresponding value stored in the address

3、 Pointer set declaration

• Declaration format
• int * pi
• char * p

* notes Contains a & And a *, The two are reciprocal operations .& Get the memory address of the variable ,* Get the contents of the variable pointed to by the pointer .

6、 ... and 、 The function of the pointer

C Using pointers in languages can ：

1. Easy to use strings
2. Effectively represent complex data structures
3. Dynamic memory allocation
4. Get more than one function return value

   7、 ... and 、 Reference resources    

1. c Summary of language pointer knowledge points
2. C language knowledge ： Arrays and pointers
3. C Summary of language pointer knowledge points - Love code network
4. Simberta blog -CSDN Blog _c Summary of language pointer knowledge points