Add First N Numbers in C – Function-Based Program with Explanation

Introduction

In this tutorial, we’ll explore how to add the first N numbers using a function in C programming. This program demonstrates the use of user-defined functions and basic loop structures, making it a perfect exercise for beginners learning C.

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C Program to Add First N Numbers Using Function

#include <stdio.h>

int addFirstNNumbers(int n) {
    int sum = 0;
    for (int i = 1; i <= n; i++) {
        sum += i;
    }
    return sum;
}

int main() {
    int n;

    printf("Enter a number: ");
    scanf("%d", &n);

    int result = addFirstNNumbers(n);
    printf("Sum of first %d numbers is: %d\n", n, result);

    return 0;
}

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Explanation

• The function addFirstNNumbers() accepts an integer n and returns the sum of numbers from 1 to n.
• The loop adds each number from 1 to n to the sum variable.
• The main() function reads input from the user and calls the function.

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Sample Output

Enter a number: 5  
Sum of first 5 numbers is: 15

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Use Cases

• Learning user-defined functions in C.
• Practicing loops and arithmetic operations.
• Building logic for numerical problems like factorials and series.