Pointers - Sharp Tutorial

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Important C Programs

Pointer

Pointer is a special type of variable used to store the memory location address of a variable.
A pointer variable may be declared as following:
int *ptr;
it can store the address but not the actual value.

Example to implement the working of pointers

#include <stdio.h>
#include <conio.h>
void main()
{
       int i = 3, *ptr ;
       ptr = &i ;    // pointer variable is storing address.
       
       //two ways to display the address
        printf("Address of i =%d ", &i) ;
        printf("Address of i =%d ", ptr) ;
      
      printf("Value of variable i = %d ", *ptr) ;  //value can be used by using ptr (pointer variable).
      printf("value of variable i = %d ", i) ;
}

Call By Value :

When we pass the normal value to a function, as we did in function topic, then it is known as call by value.

#include <stdio.h>
#include <conio.h>
void main()
{
    int n=0, f=0;
     printf("enter the number to check factorial");
     scanf("%d",&n);
    f=fact(n);
     printf("factorial of %d=%d ",n,f);
}
   int fact(int n)
      {
          int f=1;
          while(n>0)
          {
                f=f*n;
                n--;
          }
           return f;
      }

Call By Reference :

If instead of passing the actual value, only the reference is passed, then it is known as call by reference.

  #include<stdio.h>
  #include<conio.h>
  void main()
  {
     int a=10, b=20;
     printf("a= %d, b=%d", a,b) ; // a=10, b=20 
     change(&a,&b);
     printf("a= %d, b=%d", a,b) ; // a=20, b=40 changed value 
  } 
  void change(int *a, int *b)
  {
   *a=(*a)*2;.//change value here
   *b=(*b)*2;
  }

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