Sum of first and last digit of a four digit number

Posted on Apr 3, 2020

If a four-digit number is input through the keyboard, write a program in C to obtain the sum of the first and last digit of this number.

Program 

#include<stdio.h>
#include<conio.h>
void main()
{
    long int num;
	int sum = 0;

	printf("Enter a four digit number\t:");
	scanf("%ld", &num);
	sum = (num%10) + (num/1000);
	printf("\nSum of first and last digit = %ld",sum);
	getch();
}

Output 

Enter a four digit number       :9438

Sum of first and last digit = 17

Explanation

A four digit number is taken as an input from the user in the variable named 'num'. %ld is the format specifier used for long int data type. A variable named 'sum' is used to carry the sum of first and last digit of the number. sum is initialized to 0.

num % 10 operation extracts the digit of unit place i.e. last digit
For example, if num = 9438
then, num % 10 = 9438 % 10 = 8

num / 1000 operation extracts the first digit of the number.
num = 9438
then, num / 1000 = 9438 / 10 = 9

So, the statement
sum = (num%10) + (num/1000);
calculates the sum of first and last digit of the number.