Pointer In C Programming | What is pointer works on C?

A pointer or dereferencing operator in C is a powerful feature we found in C and C++. Let us see what is the point in C.

A pointer is a variable which holds the address of another variable, the direct access of the memory location. It is always initialized with a * symbol shown below.

Syntax Of Pointer:

datatype *variablename;
variablename=&var1;

For Example:

#include<stdio.h>
int main(){
	int *n;
	int a=10;
	n=&a;
	printf("the value of a is %d",a);
	printf("\nthe address of a is %d",n);
	return 0;
}

Here in the above program it shows the way to initialize and use a pointer in a program.

Output:

Types Of Pointer

The most commonly used pointers are:

Null pointer:

A null pointer is a pointer that holds a null value, which is assigned with a null value during the declaration of a pointer.

For example:

#include<stdio.h>
int main(){
	int *n=null;
	printf("the address of the pointer is %d",n);
	return 0;
}

Output:

Void pointer:

A void pointer is a pointer that is not initialized with a standard data type but is initialized with a void keyword. A void pointer is also known as a generic pointer.

Example:

#include<stdio.h>
int main(){
	void *n=NULL;
	printf("The address of the pointer is %d",n);
	return 0;
}

Here in this program we can see how a void pointer is initialized and used.

Output:

Wild pointer:

A pointer which is not initialized to anything is called a wild pointer.

Example:

#include<stdio.h>
int main(){
	int *n;
	printf("The address of the pointer is %d",n);
	return 0;
}

Output:

Here the above program shows how a wild pointer is initialized and used.

Dangling pointer:

When a pointer holds the address or memory location which has been deleted or freed is called a dangling pointer.

Example:

#include<stdio.h>
#include<stdlib.h>
int main(){
	int *n=(int *)malloc(sizeof(int));
	free(n);
	n=NULL;
	printf("The address of the pointer is %d",n);
	return 0;
}

Here the above program shows how a dangling pointer is used.

Output:

Let us take an example to demonstrate pointer, a program to swap two values of a variable using pointer.

#include<stdio.h>
void swap(int *x, int *y)
{
	int t;
	t=*x;
	*x=*y;
	*y=t;
}
int main(){
	int a,b;
	printf("\nEnter the value of the two numbers to be swapped");
	scanf("%d%d",&a,&b);
	printf("\nThe values before swapping %d %d",a,b);
	swap(&a,&b);
	printf("\nThe values after swapping %d %d",a,b);
	return 0;
}

Here in the above program it shows how to swap two variables using a pointer.

The addresses are stored and passed in a swap function and the addresses are swapped which results in the values in the variables to get swapped.

Hence through this mechanism the values of the variables get swapped.

Output: