Average of Array Elements in C: Program to Calculate Average of N Numbers

Introduction

In this tutorial, we will learn how to write a C program to calculate the average of array elements.

Finding the average of elements in an array is a common programming task. It is used in many real-world applications, such as:

• Calculating the average score of students in a class
• Finding the average temperature in weather data
• Calculating the average sales figures
• Finding the average of sensor readings

C Program to Calculate Average of Array Elements

#include <stdio.h>

int main() {
    int n, i;
    int sum = 0;
    float average;
    
    // 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];
    }
    
    // Calculate average using type casting
    average = (float)sum / n;
    
    // Display the average
    printf("\nSum of all elements: %d\n", sum);
    printf("Average of all elements: %.2f\n", average);
    
    return 0;
}

Sample Output

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

Sum of all elements: 150
Average of all elements: 30.00

Another Example (With Decimal Result):

Enter the number of elements: 4
Enter 4 elements:
10 15 25 30

Sum of all elements: 80
Average of all elements: 20.00

Example with Non-Integer Average:

Enter the number of elements: 6
Enter 6 elements:
10 20 30 40 50 60

Sum of all elements: 210
Average of all elements: 35.00

Program Explanation

Let's break down the code step by step:

1. Include Header File: #include <stdio.h> includes the standard input/output library.
2. Declare Variables:
   • int n; — stores the number of elements
   • int i; — loop counter
   • int sum = 0; — stores the sum of elements
   • float average; — stores the calculated average
3. Get User Input: Prompts the user to enter the number of elements and then reads them into the array.
4. Calculate Sum: The for loop for(i = 0; i < n; i++) iterates through each element and adds it to sum using sum = sum + arr[i];.
5. Calculate Average: average = (float)sum / n; divides the sum by the number of elements. The (float) type casting is important because:
   • If both operands are integers, C performs integer division and truncates the decimal part
   • Type casting converts the sum to float, resulting in a decimal value
6. Display Results: printf("\nSum of all elements: %d\n", sum); and printf("Average of all elements: %.2f\n", average); display the results with two decimal places.
7. Return: return 0; indicates successful program execution.

Algorithm to Calculate Average

1. Start
2. Read the number of elements (n)
3. Read n elements into the array
4. Set sum = 0
5. For i = 0 to n-1:
   • sum = sum + arr[i]
6. Set average = (float)sum / n
7. Print sum and average
8. End

Optimized Version: Single Loop

You can combine the sum calculation into the same loop where you read the input, making the program more efficient:

#include <stdio.h>

int main() {
    int n, i;
    int sum = 0;
    float average;
    
    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]);
        sum = sum + arr[i];  // Calculate sum on the fly
    }
    
    average = (float)sum / n;
    
    printf("\nSum of all elements: %d\n", sum);
    printf("Average of all elements: %.2f\n", average);
    
    return 0;
}

#include <stdio.h>

int main() {
    int n, i;
    int sum = 0;
    int count = 0;
    float average;
    
    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]);
        if(arr[i] % 2 == 0) {  // Check if even
            sum = sum + arr[i];
            count++;
        }
    }
    
    if(count > 0) {
        average = (float)sum / count;
        printf("\nSum of even elements: %d\n", sum);
        printf("Average of even elements: %.2f\n", average);
    } else {
        printf("\nNo even numbers found.\n");
    }
    
    return 0;
}

Frequently Asked Questions

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