- Write a C program to find sum of first and last digits of a number.
- Wap in C to find sum of least significant and most significant digit of a number.

Required Knowledge

- C printf and scanf functions
- While loop in C

To get the least significant digit of a number we will use ‘%’ modulus operator. Number%10 will give the least significant 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

**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; /* * Take a number as input from user */ printf("Enter a Number\n"); scanf("%d", &num); temp = num; /* get last digit of num */ lastDigit = num %10; while(num > 10){ /* Keep on removing the last digit untill num becomes less than 10(single digit) */ num = num/10; } firstDigit = num; printf("Sum of first and last digit of %d = %d", temp, firstDigit+lastDigit); getch(); return 0; }

Output

Enter a Number 2436 Sum of first and last digit of 2436 = 8

Enter a Number 2222 Sum of first and last digit of 2222 = 4

**Write a C program to find product of digits of a number using while loop.**

**Wap in C to multiply the digits of a number.**

**Required Knowledge**

- C printf and scanf functions
- While loop in C

To **multiply digits of a number** we have to remove one digit at a time, we can use ‘/’ division and ‘%’ modulus operator. Number%10 will give the least significant digit of the number, we will use it to get one digit of number at a time. To remove last least significant digit from number we will divide number by 10.

**Product of digits** of 2534 = 2 x 5 x 3 x 4 = 120

**Algorithm to find product of digits of a number**

- Get least significant digit of number (number%10) and multiply it to the product variable.
- Remove least significant digit form number (number = number/10).
- Repeat above two steps, till number is not equal to zero.

### C program to find sum of all even numbers between 1 to N using for loop

#include <stdio.h> #include <conio.h> int main() { int num, temp; long productOfDigit = 1; /* * Take a number as input from user */ printf("Enter a Number\n"); scanf("%d", &num); temp = num; while(num != 0){ /* get the least significant digit(last digit) of number and multiply it to productofDigit */ productOfDigit *= num % 10; /* remove least significant digit(last digit) form number */ num = num/10; } printf("Product of digits of %d = %ld", temp, productOfDigit); getch(); return 0; }

Output

Enter a Number 2436 Product of digits of 2436 = 144

Enter a Number 2222 Product of digits of 2436 = 16