In this C Program, we will find sum of first and last digits of a number. To get the last digit of a number we will use '%' modulus operator. Number%10 will give the last digit of the number. Then we will remove one digit at a time form number using below mentioned algorithm and then store the most significant digit in firstDigit variable.
Sum of first and last digits of 2534 = 2 + 4 = 6 
Required Knowledge
Algorithm to find first and last digits of a number
- Get least significant digit of number (number%10) and store it in lastDigit variable.
 - Remove least significant digit form number (number = number/10).
 - Repeat above two steps, till number is greater than 10.
 - The remaining number is the first digit of number.
 
C program to find sum of first and last digits of a number
#include <stdio.h>
int main() {  
    int num, temp, firstDigit, lastDigit, sum;  
   
    printf("Enter a Number\n"); 
    scanf("%d", &num);  
    temp = num;
    
    /* get last digit of num */
    lastDigit = num %10;
    
    while(num > 10){
        num = num/10;
    } 
    firstDigit = num;
    sum = firstDigit + lastDigit;
    printf("Sum of first and last digit = %d",temp,sum);  
  
    return 0;  
}
Output
Enter a Number 2436 Sum of first and last digit = 8
Enter a Number 2222 Sum of first and last digit = 4
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