The pointer is really profound!!!

Catalog

Understand the pointer ：

The address of the time variable pointed to by the pointer , And you can directly change the value of the variable through the pointer

True mystery ：

Ordinary function exchange value

Use the pointer to exchange values in the function

  * 3. Pass address to pointer with function

summary ：

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Understand the pointer ：

The address of the time variable pointed to by the pointer , And you can directly change the value of the variable through the pointer

for example ：

#include<stdio.h>
int main()
{
	int a = 0;             // Definition int Type variable 
    int* p = &a;           // Definition int Type pointer and point to a The address of （& Address ）
    *p = 1;                //p The value of the address pointed to by the pointer is assigned 1, amount to a=1
	printf("%d\n", a); 
	return 0;
}

  result a = 1

 

 

  First ： The type of pointer definition must be the same as the type of the indicated variable . As shown in the above figure int type .

secondly ： Defining a pointer can be understood as first int* p; Again p = &a; （p Point to a The address of ） This is also written correctly , What I wrote above is equivalent to 2 individual p Merge into 1 individual p To write .

Last ：*p Is equal to a Value , Namely *p == a; therefore *p change ,a The value of should also be changed .

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True mystery ：

1. Ordinary function exchange value

     Change the value of the passed variable in the function without a pointer

   #include<stdio.h>
   void hanshu(int b)           // Function interpretation     a The value to b
   {
   	b = 1;                   // Make... In a function b The assignment is 1
   }
   int main()
   {
   	int a = 0;
   	hanshu(a);               // Function call 
   	printf("%d\n", a);
   	return 0;
   }

   result ：a = 0

2. Use the pointer to exchange values in the function

          It is still a variable , Use pointers in functions

#include<stdio.h>
void hanshu(int b)        // Function passes value to b
{
	int* p = &b;          // The pointer p Point to b The address of 
	*p = 1;               // The pointer p Point to b The value of the address of is assigned 1
}
int main()
{
	int a = 0;
	hanshu(a);            // Function call 
	printf("%d\n", a);
	return 0;
}

  result ：a = 0; Note that the pointer definition in the function cannot be changed main Value passing variables in functions

  * 3. Pass address to pointer with function

     

#include<stdio.h>
void hanshu(int *p)         // Function interpretation makes a The address of is passed to p（ Equivalent to pointer p Point to a The address of ）
{ 
 	*p = 1;                 // The pointer p Point to a The value of the address of is assigned 1
}
int main()
{
	int a = 0;
	hanshu(&a);             // Function call 
	printf("%d\n", a);
	return 0;
}

  result ：a = 1

 

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summary ：

1. It can be seen that , The value passed in an ordinary function cannot be changed main The value of a variable in a function

2. Pass address with function , Receiving with a pointer can be changed in a function main The value of a variable in a function , This is also the most important pointer usage .

Thank you for reading ！！！