Largest of two numbers using pointers

Posted on Apr 12, 2020

C program to find largest of two numbers using pointers.

Program 

#include<stdio.h>
#include<conio.h>
void main()
{
	int num1, num2;
    int *ptr1, *ptr2;

    printf("Enter the first number\t:");
    scanf("%d",&num1);
    printf("Enter the second number\t:");
    scanf("%d",&num2);

    ptr1 = &num1;
    ptr2 = &num2;

    if(*ptr1 > *ptr2)
        printf("\n%d is greater",*ptr1);
    else if(*ptr1 < *ptr2)
        printf("\n%d is greater",*ptr2);
    else
        printf("\nBoth the numbers are equal");

    getch();
}

Output 

********** Run1 ********** 

Enter the first number  :5
Enter the second number :9

9 is greater


********** Run2 ********** 

Enter the first number  :7
Enter the second number :3

7 is greater


********** Run3 ********** 

Enter the first number  :4
Enter the second number :4

Both the numbers are equal

Explanation

In the above program, two variables 'num1' and 'num2' are taken, and two pointer variables '*ptr1' and '*ptr2' are also taken, ptr1 points to num1 and ptr2 points to num2 using the statements
ptr1 = &num1;
ptr2 = &num2;
ptr1 contains the address of variable num1 and ptr2 contains address of variable num2.

Let, first number entered by yser be 9 and second number ne 5.
*ptr1 means "value at the address contained in ptr1". ptr1 contains the address of num1. so, *ptr1 means "value at num1" which is the first number entered by the user i.e. 9
Similarly, *ptr2 = 5

if - else construct is used to find the greater of two numbers.
  • *ptr1 > *ptr2
    • If this condition evaluates to true, then first number is greater
  • *ptr1 < *ptr2
    • If this condition evaluates to true, then second number is greater
  • If both the above conditions result in false, then both the numbers are equal.
    •