C++ while Loop Solutions and Examples

Explore solved C++ while loop exercises, including a multiplication table, algorithm analysis, dry run, complete code, code explanation, and sample output.

Contents

• Solution: LOOP-COD-006 — Multiplication Table

Solution: LOOP-COD-006 — Multiplication Table

1. Problem Analysis

The task is to write a C++ program that asks the user to enter an integer and displays its multiplication table from 1 to 10 using a while loop.

Input:

• One integer entered by the user.

Processing:

• Initialize a counter variable with 1.
• Multiply the entered number by the counter.
• Increase the counter by 1 after each iteration.
• Repeat until the counter becomes greater than 10.

Output:

• Display the multiplication table from 1 to 10.

Programming concepts required:

• Variables
• User input and output
• while loop
• Arithmetic multiplication operator (*)
• Increment operator (++)

2. Algorithm / Pseudocode

Algorithm

1. Start the program.
2. Declare two integer variables: num and i.
3. Ask the user to enter a number.
4. Store the entered number in num.
5. Initialize i = 1.
6. While i is less than or equal to 10:
   • Calculate num * i.
   • Display the multiplication expression and its result.
   • Increase i by 1.
7. Stop the loop when i becomes greater than 10.
8. End the program.

Pseudocode

START

DECLARE num, i

DISPLAY "Enter a number: "
INPUT num

SET i = 1

WHILE i <= 10
    result = num * i
    DISPLAY num, " x ", i, " = ", result
    i = i + 1
END WHILE

STOP

3. Dry Run Table

A dry run helps us understand how the while loop executes step by step.

Given input: 7

Initially:

• num = 7
• i = 1

What happens after the 10th iteration?

• The value of i becomes 11.
• The condition i <= 10 becomes false.
• The loop terminates.

4. Complete C++ Code

#include <iostream>
using namespace std;

int main()
{
    int num, i;

    cout << "Enter a number: ";
    cin >> num;

    i = 1;

    while (i <= 10)
    {
        cout << num << " x " << i
             << " = " << num * i << endl;

        i++;
    }

    return 0;
}

5. Code Explanation

Let’s understand the important parts of the program.

A. Declare variables

int num, i;

• num stores the integer entered by the user.
• i works as a counter to control the loop.

B. Get input from the user

cout << "Enter a number: ";
cin >> num;

The program asks the user to enter an integer and stores it in num.

For example, if the user enters 7, then num = 7.

C. Initialize the counter

i = 1;

The counter starts at 1 because we need to display the multiplication table from 1 to 10.

D. Understand the while loop

while (i <= 10)

This condition checks whether the counter is less than or equal to 10.

• If the condition is true, the loop body executes.
• If the condition is false, the loop stops.

E. Display the multiplication table

cout << num << " x " << i
     << " = " << num * i << endl;

This statement displays the multiplication expression and calculates its result.

For example:

• num = 7
• i = 3
• 7 * 3 = 21

Output:

7 x 3 = 21

F. Increment the counter

i++;

The ++ operator increases the value of i by 1.

For example:

• Before increment: i = 3
• After increment: i = 4

The loop then checks the condition again.

Important: Without i++, the counter would never increase, and the loop would continue indefinitely (infinite loop).

6. Sample Output

Sample Input

Enter a number: 7

Expected Output

Multiplication Table of 7
7 x 1 = 7
7 x 2 = 14
7 x 3 = 21
7 x 4 = 28
7 x 5 = 35
7 x 6 = 42
7 x 7 = 49
7 x 8 = 56
7 x 9 = 63
7 x 10 = 70

To display the heading Multiplication Table of 7, add this statement after reading the input:

cout << "Multiplication Table of " << num << endl;

7. Modification Task

Now modify the existing program to practise independently.

Task 1: Change the Table Range

Modify the program to display the multiplication table from 1 to 15 instead of 1 to 10.

Task 2: Reverse the Table

Display the multiplication table in reverse order, from 10 down to 1.

Expected output for input 5:

5 x 10 = 50
5 x 9 = 45
5 x 8 = 40
...
5 x 1 = 5

Task 3: Multiple Tables

Modify the program to ask the user for a starting number and an ending number. Display the multiplication table only within that range.