Pointer in C Language

Pointer

Pointer is a variable which used to store address of another variable.

Two operators are used in pointer:
(1.) & : It is pronounced as "Address of".
(2.) * : It is pronounced as "Value at address".
The "value at address" operator is also called "indirection" operator.

%u: It is used to print "address".

Syntax

data-type *variableName;

example:
int *p ;

Print the address of variable

In below program p variable holds 100.

&m returns the "Address of m".

%p prints the address of m.

*(&m) returns same value as m.

Program

#include <stdio.h>
#include <conio.h>

void main(){
  int m = 100 ;
 clrscr();
 printf("\nAddress of m = %p",&m);
 printf("\nValue of m = %d",m);
 printf("\nValue of m = %d",*(&m));
 getch();
}

See Output

pointer type variable example 1

In below program ptr is pointer type variable.

"ptr = &v;" means ptr contains "address of v". Now ptr using in program means we are using address of v. And *ptr using in program means we are using value of v.

Program

#include <stdio.h>
#include <conio.h>

void main(){
  int *ptr ;
  int v = 100 ;
 clrscr();
 ptr = &v ;
 printf ("\nAddress of v = %p",&v) ;
 printf ("\nAddress of v = %p",ptr) ;
 printf ("\nAddress of ptr = %p",&ptr) ;
 printf ("\nValue of ptr = %p",ptr) ;
 printf ("\nValue of v = %d",v) ;
 printf ("\nValue of v = %d",*(&v)) ;
 printf ("\nValue of v = %d",*ptr) ;
 getch();
}

See Output

pointer type variable example 2

Program

#include <stdio.h>
#include <conio.h>

void main(){
 int a,b,c;
 int m = 100;
 int *p1,*p2;
 clrscr();
 printf("\n enter value of a: ");
 scanf("%d",&a);
 printf("\n enter value of b: ");
 scanf("%d",&b);
 p1 = &a;
 p2 = &b;
 c = *p1 + *p2 + m;
 printf("\nvalue of c= %d",c);
 getch();
}

See Output

Double pointer( pointer to pointer )

Double pointer contains address of pointer type variable.

In below example **ptr2 is double pointer variable.
Example
int m = 100;
int *ptr1;
int **ptr2;

In below program ptr1 contains address of v and ptr2 contains address of ptr2.

Program

#include <stdio.h>
#include <conio.h>

void main(){
  int *ptr1 ;
  int **ptr2 ;
  int v = 100 ;
 clrscr();
 ptr1 = &v ;
 ptr2 = &ptr1 ;
 printf("\n address of v = %p",ptr1);
 printf("\n address of ptr1 = %p",ptr2);
 getch();
}

See Output

In below program, If we are using *ptr1 in program means we are using value of v and we are using **ptr2 means we are using value of v.

Program

#include <stdio.h>
#include <conio.h>

void main(){
  int *ptr1 ;
  int **ptr2 ;
  int v = 100 ;
 clrscr();
 ptr1 = &v ;
 ptr2 = &ptr1 ;
 printf("\n value of *ptr1 = %d",*ptr1);
 printf("\n value of **ptr2 = %d",**ptr2);
 printf("\n value of v = %d",v);
 getch();
}

See Output

Program

#include <stdio.h>
#include <conio.h>

void main(){
 int a,b;
 int *p1, **p2, *pp1, **pp2;
 int s1,s2,s3;
 clrscr();
  printf("\nenter value of a: ");
 scanf("%d",&a);
 printf("\nenter value of b: ");
 scanf("%d",&b);
  p1 = &a ;
 p2 = &p1 ;
  pp1 = &b ;
  pp2 = &pp1 ;
  s1 = **p2 + **pp2;
 s2 = *p1 + **pp2;
 s3 = s1 + s2;
 printf("\n value of s1 = %d",s1);
 printf("\n value of s2 = %d",s2);
 printf("\n value of s3 = %d",s3);
 getch();
}

See Output

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