C programs using while loop

 

1.write a c Program to Count the Number of Digits

#include <stdio.h>

main() {

    int n;

    int count = 0;

    printf("Enter an integer: ");

    scanf("%lld", &n);

 

    // iterate until n becomes 0

    // remove last digit from n in each iteration

    // increase count by 1 in each iteration

    while (n != 0) {

        n /= 10;     // n = n/10

        ++count;

    }

 

    printf("Number of digits: %d", count);

}

Output

Enter an integer: 3452

Number of digits: 4

2.Write a c program to find the reversed number

#include <stdio.h>

int main() {

    int n, rev = 0, remainder;

    printf("Enter an integer: ");

    scanf("%d", &n);

    while (n != 0) {

        remainder = n % 10;

        rev = rev * 10 + remainder;

        n /= 10;

    }

    printf("Reversed number = %d", rev);

    return 0;

}

 

Output

Enter an integer: 2345

Reversed number = 5432

3.write a c program to find the power

#include <stdio.h>

int main() {

    int base, exp;

    int result = 1;

    printf("Enter a base number: ");

    scanf("%d", &base);

    printf("Enter an exponent: ");

    scanf("%d", &exp);

 

    while (exp != 0) {

        result *= base;

        --exp;

    }

    printf("Answer = %lld", result);

    return 0;

}

Output

Enter a base number: 3

Enter an exponent: 4

Answer = 81

 4.write a c program to Check Palindrome

#include <stdio.h>

 main() {

    int n, reversedN = 0, remainder, originalN;

    printf("Enter an integer: ");

    scanf("%d", &n);

    originalN = n;

 

    // reversed integer is stored in reversedN

    while (n != 0) {

        remainder = n % 10;

        reversedN = reversedN * 10 + remainder;

        n /= 10;

    }

 

    // palindrome if orignalN and reversedN are equal

    if (originalN == reversedN)

        printf("%d is a palindrome.", originalN);

    else

        printf("%d is not a palindrome.", originalN);

}

 

Output

Enter an integer: 1001

1001 is a palindrome

 

5. write a c program to find the prime numbers from a interval

#include <stdio.h>

main() {

   int low, high, i, flag;

   printf("Enter two numbers(intervals ");

   scanf("%d %d", &low, &high);

   printf("Prime numbers are %d %d", low, high);

 

   while (low < high) {

      flag = 0;

 

      // ignore numbers less than 2

      if (low <= 1) {

         ++low;

         continue;

      }

 

      // if low is a non-prime number, flag will be 1

      for (i = 2; i <= low / 2; ++i) {

 

         if (low % i == 0) {

            flag = 1;

            break;

         }

      }

 

      if (flag == 0)

         printf("%d ", low);

 

      // to check prime for the next number

      // increase low by 1

      ++low;

   }

}

Output

Enter two numbers(intervals): 20

50

Prime numbers between 20 and 50 are: 23 29 31 37 41 43 47

6.write a c program to Check Armstrong Number of three digits

#include <stdio.h>

 main() {

    int num, originalNum, remainder, result = 0;

    printf("Enter a three-digit integer: ");

    scanf("%d", &num);

    originalNum = num;

 

    while (originalNum != 0) {

       // remainder contains the last digit

        remainder = originalNum % 10;

       

       result += remainder * remainder * remainder;

       

       // removing last digit from the orignal number

       originalNum /= 10;

    }

 

    if (result == num)

        printf("%d is an Armstrong number.", num);

    else

        printf("%d is not an Armstrong number.", num);

}

Output

Enter a three-digit integer: 371

371 is an Armstrong number.