Sum of Array Elements in C: Program to Find Sum of N Numbers

Introduction

In this tutorial, we will learn how to write a C program to read N numbers of elements and find the sum of elements in an array.

This is a fundamental program that helps you understand how to work with arrays in C. You will learn how to:

• Declare and initialize an array
• Read elements from the user using scanf()
• Calculate the sum using a for loop
• Display the result using printf()

C Program to Find Sum of Array Elements

#include <stdio.h>

int main() {
    int n, i;
    int sum = 0;
    
    // Ask user for number of elements
    printf("Enter the number of elements: ");
    scanf("%d", &n);
    
    // Declare array of size n
    int arr[n];
    
    // Read elements into the array
    printf("Enter %d elements:\n", n);
    for(i = 0; i < n; i++) {
        scanf("%d", &arr[i]);
    }
    
    // Calculate sum of array elements
    for(i = 0; i < n; i++) {
        sum = sum + arr[i];
    }
    
    // Display the sum
    printf("\nSum of all elements: %d\n", sum);
    
    return 0;
}

Sample Output

Enter the number of elements: 5
Enter 5 elements:
10 20 30 40 50

Sum of all elements: 150

Another Example:

Enter the number of elements: 4
Enter 4 elements:
5 15 25 35

Sum of all elements: 80

Program Explanation

Let's break down the code step by step:

1. Include Header File: #include <stdio.h> includes the standard input/output library needed for printf() and scanf().
2. Declare Variables:
   • int n; — stores the number of elements
   • int i; — loop counter
   • int sum = 0; — stores the sum of elements (initialized to 0)
3. Get User Input for N: printf("Enter the number of elements: "); prompts the user, and scanf("%d", &n); reads the value.
4. Declare the Array: int arr[n]; declares an array of size n. This is possible in modern C compilers (variable-length array).
5. Read Elements into Array: The for loop for(i = 0; i < n; i++) runs from 0 to n-1, reading each element using scanf("%d", &arr[i]);.
6. Calculate Sum: The second for loop for(i = 0; i < n; i++) iterates through each element and adds it to sum using sum = sum + arr[i];.
7. Display the Sum: printf("\nSum of all elements: %d\n", sum); prints the final sum.
8. Return: return 0; indicates successful program execution.

#include <stdio.h>

int main() {
    int n, i;
    int sum = 0;
    
    printf("Enter the number of elements: ");
    scanf("%d", &n);
    
    int arr[n];
    
    printf("Enter %d elements:\n", n);
    for(i = 0; i < n; i++) {
        scanf("%d", &arr[i]);
    }
    
    // Calculate sum of even numbers only
    for(i = 0; i < n; i++) {
        if(arr[i] % 2 == 0) {  // Check if even
            sum = sum + arr[i];
        }
    }
    
    printf("\nSum of even elements: %d\n", sum);
    return 0;
}

/* Sample Output:
Enter the number of elements: 6
Enter 6 elements:
10 15 20 25 30 35
Sum of even elements: 60
*/

Frequently Asked Questions

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