Pointers in C

A Pointer is a variable in C that contains address of another variable.

A pointer variable is denoted by

int *p; //This means p is a pointer to an integer variable

* is Value at Address operator

& is Address of Operator

int x =15; //x is an integer variable

int *ptr1 = &x //Now p contains the address of x..i.e ptr is a pointer to x

int **ptr2 = &ptr1 //And ptr2 contains the address of ptr1..so prt2 is a pointer to a pointer

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

int main()
{
    int x=15;
    int *ptr1;
    int **ptr2;

    ptr1 = &x; //Now ptr contains the address of x
    ptr2 = &ptr1; //ptr2 contains the address of ptr

    printf("\nAddress of x = %u", &x);
    printf("\nValue of x = %d", x);
    printf("\nValue of x = %d", *(&x));

    printf("\n ");
    printf("\nAddress of ptr1 = %u", &ptr1);
    printf("\nValue of ptr1 / Address of x = %d", ptr1);
    printf("\nValue at address pointed by ptr1/Value of x = %d", *ptr1);

    printf("\n ");
    printf("\nAddress of ptr2 = %u", &ptr2);
    printf("\nValue of ptr2 / Address of ptr1 = %d", ptr2);
    printf("\nValue at address pointed ptr2 / Address of x= %d", *ptr2);
    printf("\nValue at address pointed by ptr1 which is pointed by ptr2/Value of x = %d", **ptr2);

    getch();
    return 0;
}

Snapshot of the o/p

C Program printing Celsius-Fahrenheit table

Hi Friends!!

This is the 2nd Program of our Temperature Conversion Table.

This time we converted from Celsius to Fahrenheit using the formula

F = C *(9/5)+32

where

C is Celsius
F is Fahrenheit 

Here is the program

/*Program printing Celsius-Fahrenheit table*/

#include <stdio.h>

#include <conio.h>

#define LOWER 0 /* lower limit of table */

#define UPPER 200 /* upper limit */

#define STEP 10 /* step size */

 

int main()

{

     int celc;

     printf(” Celsius\t Fahrenheit\n\n “);

     for (celc = LOWER; celc <= UPPER; celc = celc + STEP)

     printf(” %d \t   %6.1f\n”, celc, celc *(9.0/5.0)+32);

    

     getch();

     return 0;   

}

Screenshot of the o/p

C Program printing Fahrenheit-Celsius table

Hi Friends!!

This is a C Program Printing Fahrenheit-Celsius table

Here we have converted from  Fahrenheit to Celsius using the formula

C = (5/9)*(F-32)

where

C is Celsius
F is Fahrenheit 

/*Program printing Fahrenheit-Celsius table*/

#include <stdio.h>

#include <conio.h>

#define LOWER 0 /* lower limit of table */

#define UPPER 200 /* upper limit */

#define STEP 10 /* step size */

 

int main()

{

    int fahr;

    printf(” Fahrenheit \t Celsius\n\n “);

    for (fahr = LOWER; fahr <= UPPER; fahr = fahr + STEP)

    printf(” %d \t   %6.1f\n”, fahr, (5.0/9.0)*(fahr-32));

 

    getch();

    return 0;  

}

Snapshot of the output

Factorial Function in C

Hi Friends

I hope you missed me. Here’s a C Program showing Factorial functionality.

/* Program demonstrating Factorial Function */

 

#include<stdio.h>

#include<conio.h>

 

//Factorial Function 1st version

int factorial1(int num)

{

      int i;

      int result = 1;

     

      for(i=1; i<=num; i++)

      {

               result = result * i;

      }

     

      return result; 

}

 

//Factorial Function 2nd version

int factorial2(int num)

{

      int i;

      int result = 1;

     

      for(i=num; i>=1; i–)

      {

               result = result * i;

      }

     

      return result; 

}

int main()

{

     int num = 3;

    

     printf(“\n ##Factorial Function in C## \n”);

    

     printf(“\n Factorial of %d is %d”, num, factorial1(num));

    

     printf(“\n Factorial of 5 is %d”, factorial2(5));

    

     getch();

     return 0;  

}

Snapshot of the o/p

Swap Function in C using Pointers

Hi Friends

This is the popular swap() function in C showing the working of Pointers as Function Arguments.

/* Program demonstrating Swap Function */

#include<stdio.h>

#include<conio.h>

 

//Swap Function in C

//pass by value

void swap(int num1, int num2)

{

     int num3;

     num3=num1;

     num1=num2;

     num2=num3; 

    

     printf(“\n Inside Swap Function \n”);

     printf(“\n num1 = %d”, num1);

     printf(“\n num2 = %d”, num2);

     printf(“\n”);

}

 

//pass by reference

void swapref(int *num1, int *num2)

{

     int num3;

     num3=*num1;

     *num1=*num2;

     *num2=num3;  

}

int main()

{

     int a, b, c;

     a=2;

     b=3;

    

     printf(“\n ~~~Swapping two Numbers in C~~~ \n”);

    

     printf(“\n Before Swapping \n”);

     

     printf(“\n a = %d”, a);

     printf(“\n b = %d”, b);

     printf(“\n”);

    

     swap(a,b);

     printf(“\n After Swapping in main (pass by value)\n”);

     printf(“\n a = %d”, a);

     printf(“\n b = %d”, b);

     printf(“\n”);

    

     printf(“\n After Swapping (pass by reference) \n”);

     swapref(&a,&b);

     

     printf(“\n a = %d”, a);

     printf(“\n b = %d”, b);

   

     getch();

     return 0;  

}

Snapshot of the o/p