D4_pointers (pointer)

 Pointers


     * Pointers are variables

     * Pointers store only address of the memory location.
       they do not store a value.

     * Pointers are declared like :-  int *ptr;

     * Address are always integer datatype , hence all  pointers need only 2 bytes


#include<stdio.h>void main(){       int a=10;    //Integer variable       int *ptr;   // Pointer variable       ptr= &a;    // address of a stored in ptr       printf("%d\n",a);  // prints value       printf("%u\n",&a); // %u used to print address       printf("%u\n",&ptr);  //65526       printf("%u\n",ptr);   // 65524       printf("%d\n",*ptr);  //10 }

Float Type:

#include<stdio.h>void main(){       float b=10.24;                  float * ptr; // 2bytes  float means the data type of the value present at this address       ptr = &b;       printf("%f\n",b);  //10.24       printf("%u\n",&b);  // 65524       printf("%u\n",ptr); // 65524       printf("%u\n",&ptr); // 65528       printf("%f\n",*ptr);  // 10.24 }

* Int A = 10; // a hold the value
* Int * PTR = & A // PTR holds the address of Variable
* Int ** PTR = & PTR // ptr1 holds the address of a pointer variable

 

# Include <stdio. h> void main () {int A = 10; int * PTR; // single pointer int ** ptr1; // double pointer PTR = & A; ptr1 = & PTR; printf ("% d \ n", a); // 10 printf ("% u \ n", PTR); // 65524% U: output address: printf ("% u \ n", & PTR); // 65526 printf ("% u \ n", * PTR ); // 10 printf ("% u \ n", ptr1); // 65526 printf ("% u \ n", & ptr1 ); // 65528 printf ("% u \ n", * ptr1); // 65524 printf ("% u \ n", ** ptr1); // 10}

Use of pointers:

#include<stdio.h>void swap(int *x,int *z);  void main()  {           int a=10, b=20;            swap(&a,&b); //call by reference              printf(" a = %d",a);            printf(" b = %d",b);  }  void swap(int *x,int *z)  {          int temp;          temp=*x;          *x=*z;          *z=temp;  }