C Program for practice

 1. Print "Hello, World!" (Basic Output)

 #include <stdio.h>

int main() {
    printf("Hello, World!\n");
    return 0;
}

2. Add Two Numbers (User Input)

#include <stdio.h>

int main() {
    int a, b, sum;
    printf("Enter two numbers: ");
    scanf("%d %d", &a, &b);
    sum = a + b;
    printf("Sum = %d\n", sum);
    return 0;
}

3. Find Odd or Even (If-Else Statement)

#include <stdio.h>

int main() {
    int num;
    printf("Enter a number: ");
    scanf("%d", &num);
    
    if (num % 2 == 0)
        printf("%d is Even\n", num);
    else
        printf("%d is Odd\n", num);
    
    return 0;
}
 

4.  Print Numbers from 1 to 10 (For Loop)

 #include <stdio.h>

int main() {
    for (int i = 1; i <= 10; i++) {
        printf("%d ", i);
    }
    printf("\n");
    return 0;
}

5. Find Factorial of a Number (Using Loop)

 #include <stdio.h>

int main() {
    int num, factorial = 1;
    printf("Enter a number: ");
    scanf("%d", &num);
    
    for (int i = 1; i <= num; i++) {
        factorial *= i;
    }
    
    printf("Factorial of %d is %d\n", num, factorial);
    return 0;
}

6. Reverse a Number (While Loop)

 #include <stdio.h>

int main() {
    int num, reversed = 0, remainder;
    printf("Enter a number: ");
    scanf("%d", &num);
    
    while (num != 0) {
        remainder = num % 10;
        reversed = reversed * 10 + remainder;
        num /= 10;
    }
    
    printf("Reversed number: %d\n", reversed);
    return 0;
}

7. Check if a Number is Prime

 #include <stdio.h>

int main() {
    int num, i, isPrime = 1;
    printf("Enter a number: ");
    scanf("%d", &num);

    if (num <= 1)
        isPrime = 0;
    else {
        for (i = 2; i * i <= num; i++) {
            if (num % i == 0) {
                isPrime = 0;
                break;
            }
        }
    }

    if (isPrime)
        printf("%d is a Prime number\n", num);
    else
        printf("%d is not a Prime number\n", num);
    
    return 0;
}

8. Swap Two Numbers (Using a Temporary Variable)

 #include <stdio.h>

int main() {
    int a, b, temp;
    printf("Enter two numbers: ");
    scanf("%d %d", &a, &b);
    
    temp = a;
    a = b;
    b = temp;
    
    printf("After swapping: a = %d, b = %d\n", a, b);
    return 0;
}

9. Find the Largest Number in an Array

 #include <stdio.h>

int main() {
    int n, i, max;
    printf("Enter number of elements: ");
    scanf("%d", &n);

    int arr[n];
    printf("Enter %d numbers: ", n);
    for (i = 0; i < n; i++) {
        scanf("%d", &arr[i]);
    }

    max = arr[0];
    for (i = 1; i < n; i++) {
        if (arr[i] > max)
            max = arr[i];
    }

    printf("Largest number = %d\n", max);
    return 0;
}

10. Reverse a String (Using Loop)

 #include <stdio.h>
#include <string.h>

int main() {
    char str[100];
    printf("Enter a string: ");
    scanf("%s", str);

    int len = strlen(str);
    printf("Reversed string: ");
    for (int i = len - 1; i >= 0; i--) {
        printf("%c", str[i]);
    }
    printf("\n");

    return 0;
}

11. Fibonacci Series Using Recursion

 #include <stdio.h>

int fibonacci(int n) {
    if (n <= 1)
        return n;
    return fibonacci(n - 1) + fibonacci(n - 2);
}

int main() {
    int n;
    printf("Enter number of terms: ");
    scanf("%d", &n);

    printf("Fibonacci series: ");
    for (int i = 0; i < n; i++) {
        printf("%d ", fibonacci(i));
    }
    printf("\n");

    return 0;
}