Initial understanding of pointer variables

1、 Define a pointer variable

#define  _CRT_SECURE_NO_WARNINGS
#include <stdio.h>


int main()
{
	int a = 10;//a Space to be allocated in memory --4 byte 
	printf("%p\n", &a);//%p Designed for printing addresses 

	int* pa = &a;//pa It is used for storing addresses , stay C In language pa It's called pointer variable 
	//* explain pa It's a pointer variable 
	//int explain pa Modification is int Object of type 

	char b = 'w';
	char* pa1 = &b;
}

a Space to be allocated in memory --4 byte
%p Designed for printing addresses

int* pa = &a;//pa It is used for storing addresses , stay C In language pa It's called pointer variable
* explain pa It's a pointer variable
int explain pa Modification is int Object of type

2、 Pointer size

How to determine the size of a pointer ？

#define  _CRT_SECURE_NO_WARNINGS
#include <stdio.h>

int main()
{
	printf("%d\n", sizeof(char*));
	printf("%d\n", sizeof(int*));
	printf("%d\n", sizeof(float*));
	printf("%d\n", sizeof(double*));
	printf("%d\n", sizeof(short*));
	printf("%d\n", sizeof(long*));
	printf("%d\n", sizeof(long long*));
	// All sizes are 8 byte 
}

The output is as follows

so , Pointer sizes are 8 byte , The pointer size is the same , This is because pointers are used to store addresses , How much space the pointer needs depends on how much space the address storage needs ; such as 32 Bit machine pointer size is 4 byte ,64 Bit machine pointer size is 8 byte .

3、 Use the dereference operator * To change the value of a local variable

There is the following code snippet

#define  _CRT_SECURE_NO_WARNINGS
#include <stdio.h>


int main()
{
	int a = 25;
	int* pa = &a;

	*pa = 56;//*   Is the dereference operator ,*pa It is through pa find a Address changed after a Value 
	printf("%d\n", a);
}

Output is as follows

so , among a The value of , This is because *  Dereference operator ,*pa It is through pa find a Address changed after a Value .