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25 simple C programs must learn in C Programming language #3

 Here are 25 simple C programs:


### Program 1: Hello World


```c

#include <stdio.h>


int main() {

    printf("Hello, World!\n");

    return 0;

}

```


### Program 2: Add Two Numbers


```c

#include <stdio.h>


int main() {

    int num1 = 5, num2 = 7, sum;

    sum = num1 + num2;

    printf("Sum: %d\n", sum);

    return 0;

}

```


### Program 3: Find Maximum of Two Numbers


```c

#include <stdio.h>


int main() {

    int num1 = 10, num2 = 7;

    if (num1 > num2) {

        printf("%d is the maximum.\n", num1);

    } else {

        printf("%d is the maximum.\n", num2);

    }

    return 0;

}

```


### Program 4: Factorial Calculation


```c

#include <stdio.h>


int main() {

    int num = 5, factorial = 1, i;

    for (i = 1; i <= num; i++) {

        factorial *= i;

    }

    printf("Factorial of %d is %d\n", num, factorial);

    return 0;

}

```


### Program 5: Print Fibonacci Series


```c

#include <stdio.h>


int main() {

    int n = 10, first = 0, second = 1, next, i;

    for (i = 0; i < n; i++) {

        if (i <= 1)

            next = i;

        else {

            next = first + second;

            first = second;

            second = next;

        }

        printf("%d\n", next);

    }

    return 0;

}

```


### Program 6: Check if a Number is Prime


```c

#include <stdio.h>


int main() {

    int num = 17, i, isPrime = 1;

    for (i = 2; i <= num/2; i++) {

        if (num % i == 0) {

            isPrime = 0;

            break;

        }

    }

    if (isPrime)

        printf("%d is prime.\n", num);

    else

        printf("%d is not prime.\n", num);

    return 0;

}

```


### Program 7: Reverse a Number


```c

#include <stdio.h>


int main() {

    int num = 12345, reversedNum = 0, remainder;

    while (num != 0) {

        remainder = num % 10;

        reversedNum = reversedNum * 10 + remainder;

        num /= 10;

    }

    printf("Reversed number: %d\n", reversedNum);

    return 0;

}

```


### Program 8: Check if a Number is Palindrome


```c

#include <stdio.h>


int main() {

    int num = 12321, reversedNum = 0, originalNum, remainder;

    originalNum = num;

    while (num != 0) {

        remainder = num % 10;

        reversedNum = reversedNum * 10 + remainder;

        num /= 10;

    }

    if (originalNum == reversedNum)

        printf("%d is a palindrome.\n", originalNum);

    else

        printf("%d is not a palindrome.\n", originalNum);

    return 0;

}

```


### Program 9: Calculate Sum of Natural Numbers


```c

#include <stdio.h>


int main() {

    int n = 5, sum = 0, i;

    for (i = 1; i <= n; i++) {

        sum += i;

    }

    printf("Sum of first %d natural numbers: %d\n", n, sum);

    return 0;

}

```


### Program 10: Generate Multiplication Table


```c

#include <stdio.h>


int main() {

    int num = 5, i;

    for (i = 1; i <= 10; i++) {

        printf("%d x %d = %d\n", num, i, num*i);

    }

    return 0;

}

```


### Program 11: Calculate Factorial Using a Function


```c

#include <stdio.h>


int factorial(int num) {

    if (num == 0)

        return 1;

    return num * factorial(num - 1);

}


int main() {

    int num = 5;

    int result = factorial(num);

    printf("Factorial of %d is %d\n", num, result);

    return 0;

}

```


### Program 12: Find GCD (Greatest Common Divisor) of Two Numbers


```c

#include <stdio.h>


int gcd(int a, int b) {

    if (b == 0)

        return a;

    return gcd(b, a % b);

}


int main() {

    int num1 = 24, num2 = 36;

    int result = gcd(num1, num2);

    printf("GCD of %d and %d is %d\n", num1, num2, result);

    return 0;

}

```


### Program 13: Calculate Power of a Number


```c

#include <stdio.h>


int power(int base, int exponent) {

    int result = 1;

    while (exponent > 0) {

        result *= base;

        exponent--;

    }

    return result;

}


int main() {

    int base = 2, exponent = 3;

    int result = power(base, exponent);

    printf("%d raised to the power of %d is %d\n", base, exponent, result);

    return 0;

}

```


### Program 14: Check Leap Year


```c

#include <stdio.h>


int isLeapYear(int year) {

    if ((year % 4 == 0 && year % 100 != 0) || (year % 400 == 0))

        return 1;

    else

        return 0;

}


int main() {

    int year = 2020;

    if (isLeapYear(year))

        printf("%d is a leap year.\n", year);

    else

        printf("%d is not a leap year.\n", year);

    return 0;

}

```


### Program 15: Count Number of Digits in an Integer


```c

#include <stdio.h>


int countDigits(int num) {

    int count = 0;

    while (num != 0) {

        num /= 10;

        count++;

    }

    return count;

}


int main() {

    int num = 12345;

    int result = countDigits(num);

    printf("Number of digits in %d is %d\n", num, result);

    return 0;

}

```


### Program 16: Find Largest Element in an Array


```c

#include <stdio.h>


int findLargest(int arr[], int size) {

    int max = arr[0];

    for (int i = 1; i < size; i++) {

        if (arr[i] > max) {

            max = arr[i];

        }

    }

    return max;

}


int main() {

    int arr[] = {12, 56, 87, 23, 89, 65};

    int size = sizeof(arr) / sizeof(arr[0]);

    int result = findLargest(arr, size);

    printf("Largest element in the array is %d\n", result);

    return 0;

}

```


### Program 17: Reverse an Array


```c

#include <stdio.h>


void reverseArray(int arr[], int size) {

    int temp, start = 0, end = size - 1;

    while (start < end) {

        temp = arr[start];

        arr[start] = arr[end];

        arr[end] = temp;

        start++;

        end--;

    }

}


int main() {

    int arr[] = {1, 2, 3, 4, 5};

    int size = sizeof(arr) / sizeof(arr[0]);

    reverseArray(arr, size);

    printf("Reversed Array: ");

    for (int i = 0; i < size; i++) {

        printf("%d ", arr[i]);

    }

    printf("\n");

    return 0;

}

```


### Program 18: Check for Armstrong Number


```c

#include <stdio.h>

#include <math.h>


int isArmstrong(int num) {

    int originalNum = num, sum = 0, digit;

    int n = log10(num) + 1;

    while (num > 0) {

        digit = num % 10;

        sum += pow(digit, n);

        num /= 10;

    }

    return (sum == originalNum);

}


int main() {

    int num = 153;

    if (isArmstrong(num))

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

    else

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

    return 0;

}

```


### Program 19: Find Factorial Using Recursion


```c

#include <stdio.h>


int factorial(int num) {

    if (num == 0)

        return 1;

    return num * factorial(num - 1);

}


int main() {

    int num = 5;

    int result = factorial(num);

    printf("Factorial of %d is %d\n", num, result);

    return 0;

}

```


### Program 20: Calculate Simple Interest


```c

#include <stdio.h>


float calculateSimpleInterest(float principal, float rate, float time) {

    return (principal * rate * time) / 100;

}


int main() {

    float principal = 1000, rate = 5.0, time = 2.5;

    float interest = calculateSimpleInterest(principal, rate, time);

    printf("Simple Interest: %f\n", interest);

    return 0;

}

```


### Program 21: Find LCM (Least Common Multiple) of Two Numbers


```c

#include <stdio.h>


int findLCM(int a, int b) {

    int max = (a > b) ? a : b;

    while (1) {

        if (max % a == 0 && max % b == 0)

            return max;

        max++;

    }

}


int main() {

    int num1 = 12, num2 = 18;

    int result = findLCM(num1, num2);

    printf("LCM of %d and %d is %d\n", num1, num2, result);

    return 0;

}

```


### Program 22: Calculate Power Using Recursion


```c

#include <stdio.h>


int power(int base, int exponent) {

    if (exponent == 0)

        return 1;

    return base * power(base, exponent - 1);

}


int main() {

    int base = 2, exponent = 3;

    int result = power(base, exponent);

    printf("%d raised to the power of %d is %d\n", base, exponent, result);

    return 0;

}

```


### Program 23: Check if a String is Palindrome


```c

#include <stdio.h>

#include <string.h>


int isPalindrome(char str[]) {

    int len = strlen(str);

    for (int i = 0; i < len / 2; i++) {

        if (str[i] != str[len - 1 - i])

            return 0;

    }

    return 1;

}


int main() {

    char str[] = "radar";

    if (isPalindrome(str))

        printf("%s is a palindrome.\n", str);

    else

        printf("%s is not a palindrome.\n", str);

    return 0;

}

```


### Program 24: Find Prime Numbers in a Range


```c

#include <stdio.h>


int isPrime(int num) {

    if (num < 2) return 0;

    for (int i = 2; i <= num/2; i++) {

        if (num % i == 0) return 0;

    }

    return 1;

}


int main() {

    int start = 10, end = 50;

    printf("Prime numbers between %d and %d are: ", start, end);

    for (int i = start; i <= end; i++) {

        if (isPrime(i))

            printf("%d ", i);

    }

    printf("\n");

    return 0;

}

```


### Program 25: Calculate Compound Interest


```c

#include <stdio.h>

#include <math.h>


float calculateCompoundInterest(float principal, float rate, float time) {

    return principal * pow((1 + rate / 100), time) - principal;

}


int main() {

float principal = 1000, rate = 5.0, time =2.5; float interest = 


calculateCompoundInterest(principal, rate, time);

   

 printf("Compound Interest: %f\n", interest);

    return 0;

}

```


These are some simple C programs covering a range of concepts. As you practice and gain confidence, you can try more complex programs and explore advanced topics in C programming.

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