📚 In this tutorial, you will learn:

How to read 10 numbers from the keyboard using for loop in C
How to calculate the sum of 10 numbers
How to calculate the average of 10 numbers
How to display the sum and average using printf()

Introduction

In this tutorial, we'll learn how to write a C program using a for loop to read 10 numbers from the keyboard and find their sum and average. This is a fundamental program that helps you understand how to use loops for repeated input operations and arithmetic calculations.

The program uses a for loop to iterate 10 times, each time taking a number input from the user. It adds each number to a running total, and after the loop completes, it calculates the average by dividing the total by 10.

💡 Key Concept: The for loop is ideal when you know the exact number of iterations. Here, we need exactly 10 inputs, so the for loop is a perfect choice.

Program Code

C Program to Find Sum and Average of 10 Numbers Using For Loop

#include <stdio.h>

int main() {
    int i, total = 0, n;
    float avg = 0.0;

    printf("Enter any 10 Numbers\n");

    for (i = 1; i <= 10; i++) {
        scanf("%d", &n);
        total += n;
    }

    avg = total / 10.0;
    printf("\nTotal = %d", total);
    printf("\nAverage = %.2f", avg);

    return 0;
}

Program Output

Enter any 10 Numbers
11
10
6
4
9
8
3
7
4
10

Total = 72
Average = 7.20

Program Explanation

Let's break down this program step by step to understand how it works:

1. Header File Inclusion:

#include <stdio.h>

This includes the standard input/output library, which provides functions like printf() and scanf().

2. Variable Declaration:

int i, total = 0, n;
float avg = 0.0;

i is the loop counter, total stores the sum of all numbers (initialized to 0), n stores each input number, and avg stores the average (initialized to 0.0).

3. User Prompt:

printf("Enter any 10 Numbers\n");

This displays a message asking the user to enter 10 numbers.

4. For Loop:

for (i = 1; i <= 10; i++) {
    scanf("%d", &n);
    total += n;
}

The loop runs 10 times (i from 1 to 10). In each iteration:

scanf("%d", &n) reads a number from the user and stores it in n
total += n adds the number to the running total

5. Average Calculation:

avg = total / 10.0;

The average is calculated by dividing the total by 10.0 (using 10.0 instead of 10 ensures floating-point division).

6. Display Result:

printf("\nTotal = %d", total);
printf("\nAverage = %.2f", avg);

The program prints the total and average. %.2f formats the average to 2 decimal places.

7. Return Statement:

return 0;

Indicates that the program executed successfully and returns control to the operating system.

Practice Exercises

📝 Exercise 1: Sum and Average of N Numbers

Modify the program to read N numbers (where N is provided by the user) and find their sum and average.

Show Solution

#include <stdio.h>

int main() {
    int i, n, total = 0, num;
    float avg;

    printf("How many numbers? ");
    scanf("%d", &n);

    for(i = 1; i <= n; i++) {
        printf("Enter number %d: ", i);
        scanf("%d", &num);
        total += num;
    }

    avg = total / (float)n;
    printf("\nTotal = %d", total);
    printf("\nAverage = %.2f", avg);

    return 0;
}

📝 Exercise 2: Sum and Average Using While Loop

Rewrite the program using a while loop instead of a for loop.

Show Solution

#include <stdio.h>

int main() {
    int i = 1, total = 0, n;
    float avg = 0.0;

    printf("Enter any 10 Numbers\n");

    while(i <= 10) {
        scanf("%d", &n);
        total += n;
        i++;
    }

    avg = total / 10.0;
    printf("\nTotal = %d", total);
    printf("\nAverage = %.2f", avg);

    return 0;
}

Frequently Asked Questions

1. Why do we use a for loop to read 10 numbers?

We use a for loop because we know exactly how many numbers we need to read (10). The for loop provides a clean and structured way to repeat a block of code a specific number of times.

2. Why do we divide by 10.0 instead of 10?

Dividing by 10.0 ensures floating-point division. If we divide by 10 (an integer), the result would be an integer (integer division), which would truncate the decimal part.

3. What happens if the user enters a non-integer value?

If the user enters a non-integer value, the scanf() function will fail and the program may produce unexpected results. In a production program, you would add input validation to handle such cases.

4. Can we use a do-while loop for this program?

Yes, you can use a do-while loop. However, a for loop is more appropriate here because we know exactly 10 iterations are needed. A do-while loop is better when the number of iterations is unknown or when you need to execute at least once.

💡 Tip: Always initialize your variables before using them. In this program, total and avg are initialized to 0 to avoid garbage values.

🎯 Key Takeaway: The for loop is perfect for situations where you know the exact number of iterations. This program demonstrates how to read multiple inputs and perform calculations, which is a fundamental skill in C programming.

Previous Topic: -->> Lowercase Alphabets Using For Loop || Next topic: -->> Multiplication Table Using For Loop

🔥 For Loop Assignments (Practice Set 1)

Practice the most important C for loop programs asked in exams and interviews.

1. Display First N Natural Numbers
Write a program in C using for loop to display the first N natural numbers.
2. Print Odd Numbers from 1 to N
Write a program in C to print ODD numbers from 1 to N using for loop.
3. Print Even Numbers from 1 to N
Write C program to show EVEN numbers from 1 to N using for loop.
4. Print Uppercase Alphabets
Write a program in C to print all uppercase alphabets using for loop.
5. Print Lowercase Alphabets
Write a program in C to display all lowercase alphabets using for loop.
6. Sum and Average of 10 Numbers
Write a program in C using for loop to read 10 numbers and find their sum and average.
7. Multiplication Table
Write C program to read an integer and print its multiplication table using for loop.
8. Positive, Negative or Zero Check
C program to check entered number is ZERO, POSITIVE or NEGATIVE using for loop.
9. Factorial of a Number
Write a program in C to find factorial of a number using for loop.
10. Sum and Average of N Numbers
Find sum and average of first N natural numbers using for loop.

📘 For Loop Assignments (Practice Set 2)

1. Reverse a Number - Reverse a given number using for loop.
2. Armstrong Number - Check if a number is Armstrong using for loop.
3. Fibonacci Series - Print Fibonacci series up to N using for loop.
4. Prime Number Check - Check if a number is prime using for loop.
5. Decimal to Binary - Convert decimal to binary using for loop.
6. Sum of Squares - 1²+2²+3²+...+N² using for loop.
7. Sum of Factorial Series - 1/1! + 2/2! + ... + N/N! using for loop.
8. Harmonic Series - 1 + 1/2 + 1/3 + ... + 1/N using for loop.

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