20 C programming examples for beginners

Each example below is short, self-contained, and ready to paste straight into the C compiler to run. Work through them in order — they build on each other, starting with basic output and ending with simple algorithms.

1. Hello, World!

Every C program needs a main() function — this is where execution starts.

#include <stdio.h>

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

2. Adding two numbers

Reads two integers using scanf() and prints their sum.

#include <stdio.h>

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

3. Checking even or odd

Uses the modulus operator % to test divisibility by 2.

#include <stdio.h>

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

4. Finding the largest of three numbers

#include <stdio.h>

int main() {
    int a, b, c;
    scanf("%d %d %d", &a, &b, &c);
    int largest = a;
    if (b > largest) largest = b;
    if (c > largest) largest = c;
    printf("Largest = %d\n", largest);
    return 0;
}

5. Factorial of a number

A classic loop-based example — multiplies numbers from 1 up to n.

#include <stdio.h>

int main() {
    int n;
    long long fact = 1;
    scanf("%d", &n);
    for (int i = 1; i <= n; i++)
        fact *= i;
    printf("Factorial = %lld\n", fact);
    return 0;
}

6. Fibonacci series

#include <stdio.h>

int main() {
    int n, a = 0, b = 1;
    scanf("%d", &n);
    for (int i = 0; i < n; i++) {
        printf("%d ", a);
        int next = a + b;
        a = b;
        b = next;
    }
    printf("\n");
    return 0;
}

7. Checking a prime number

#include <stdio.h>

int main() {
    int n, isPrime = 1;
    scanf("%d", &n);
    if (n < 2) isPrime = 0;
    for (int i = 2; i * i <= n; i++) {
        if (n % i == 0) { isPrime = 0; break; }
    }
    printf(isPrime ? "Prime\n" : "Not Prime\n");
    return 0;
}

8. Reversing a number

#include <stdio.h>

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

9. Sum of digits

#include <stdio.h>

int main() {
    int n, sum = 0;
    scanf("%d", &n);
    while (n != 0) {
        sum += n % 10;
        n /= 10;
    }
    printf("Sum of digits = %d\n", sum);
    return 0;
}

10. Palindrome check (number)

#include <stdio.h>

int main() {
    int n, original, reversed = 0;
    scanf("%d", &n);
    original = n;
    while (n != 0) {
        reversed = reversed * 10 + n % 10;
        n /= 10;
    }
    printf(original == reversed ? "Palindrome\n" : "Not a Palindrome\n");
    return 0;
}

11. Printing a multiplication table

#include <stdio.h>

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

12. Right-angled triangle pattern

#include <stdio.h>

int main() {
    int rows = 5;
    for (int i = 1; i <= rows; i++) {
        for (int j = 1; j <= i; j++)
            printf("* ");
        printf("\n");
    }
    return 0;
}

13. Swapping two numbers (without a third variable)

#include <stdio.h>

int main() {
    int a = 5, b = 10;
    a = a + b;
    b = a - b;
    a = a - b;
    printf("a = %d, b = %d\n", a, b);
    return 0;
}

14. Working with arrays: finding the maximum

#include <stdio.h>

int main() {
    int arr[] = {12, 45, 3, 67, 21};
    int n = 5, max = arr[0];
    for (int i = 1; i < n; i++)
        if (arr[i] > max) max = arr[i];
    printf("Maximum = %d\n", max);
    return 0;
}

15. Bubble sort

#include <stdio.h>

int main() {
    int arr[] = {5, 2, 9, 1, 5, 6};
    int n = 6;
    for (int i = 0; i < n - 1; i++)
        for (int j = 0; j < n - i - 1; j++)
            if (arr[j] > arr[j + 1]) {
                int temp = arr[j];
                arr[j] = arr[j + 1];
                arr[j + 1] = temp;
            }
    for (int i = 0; i < n; i++)
        printf("%d ", arr[i]);
    printf("\n");
    return 0;
}

16. String length without `strlen()`

#include <stdio.h>

int main() {
    char str[] = "Hello";
    int length = 0;
    while (str[length] != '\0')
        length++;
    printf("Length = %d\n", length);
    return 0;
}

17. Checking if a string is a palindrome

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

int main() {
    char str[] = "madam";
    int len = strlen(str);
    int isPalindrome = 1;
    for (int i = 0; i < len / 2; i++) {
        if (str[i] != str[len - 1 - i]) { isPalindrome = 0; break; }
    }
    printf(isPalindrome ? "Palindrome\n" : "Not a Palindrome\n");
    return 0;
}

18. Using functions: a simple calculator

#include <stdio.h>

int add(int a, int b) { return a + b; }
int subtract(int a, int b) { return a - b; }

int main() {
    int x = 10, y = 4;
    printf("Sum = %d\n", add(x, y));
    printf("Difference = %d\n", subtract(x, y));
    return 0;
}

19. Using pointers

#include <stdio.h>

int main() {
    int num = 25;
    int *ptr = &num;
    printf("Value = %d\n", *ptr);
    printf("Address = %p\n", (void*)ptr);
    return 0;
}

20. Structures: storing student data

#include <stdio.h>

struct Student {
    char name[30];
    int marks;
};

int main() {
    struct Student s1 = {"Aman", 88};
    printf("Name: %s, Marks: %d\n", s1.name, s1.marks);
    return 0;
}

What to try next

Once these feel comfortable, look into pointers with arrays, dynamic memory using malloc(), and file handling with fopen(). If you hit a wall with an error message while experimenting, check our guide on common C compiler errors and how to fix them.

← Try these in the C compiler