Loops: For, While and Do-While

Imagine playing a game where you have to clap every time the number increases. If you were to clap 10 times, would you do it one by one manually, or ask someone (or something!) to repeat it for you?

Computers love repeating things.
They can do the same action 10, 100, or even 1,000,000 times without getting tired.
This superpower comes from loops.

Today, you’ll learn how to make C# repeat tasks automatically, and you’ll build your first number-game program.

Multiplication Table & Number Games

You’ll write a program that prints a multiplication table, for example, for the number 5:

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5 x 1 = 5  
5 x 2 = 10  
5 x 3 = 15  
...  
5 x 10 = 50

Then you’ll add a fun number game that prints all numbers from 1 to 20, skipping 10, and stopping at 15.

This will teach you looping + break + continue.

Why Loops Matter

Imagine writing:

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Console.WriteLine(1);
Console.WriteLine(2);
Console.WriteLine(3);
...

It would take forever, and look silly.

Loops make your programs:

• shorter
• faster
• smarter
• more dynamic

Now let’s meet the 3 loops that power almost every app you’ll ever build.

The For Loop (Best When You Know the Count)

Use a for loop when you know how many times you want to repeat an action.

Example:

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for (int i = 1; i <= 5; i++)
{
    Console.WriteLine(i);
}

This prints 1 to 5.

The While Loop (Best for Repeating Until Something Happens)

Use while when you don’t know how many times you’ll repeat, but you know the condition.

Example:

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int count = 1;

while (count <= 5)
{
    Console.WriteLine(count);
    count++;
}

Same output, different purpose.

The Do-While Loop (Runs At Least Once)

do-while always runs the block before checking the condition.

Example:

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int x = 1;

do
{
    Console.WriteLine(x);
    x++;
}
while (x <= 5);

Even if the condition is false, it will run once, great for menus and retry screens.

Counting Up

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for (int i = 1; i <= 10; i++)

Counting Down

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for (int i = 10; i >= 1; i--)

Skipping Values (continue)

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if (i == 5) continue;

Stopping Early (break)

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if (i == 8) break;

These patterns appear everywhere, from games to billing apps.

break

Stops the loop immediately.

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if (i == 10)
    break;

continue

Skips the current iteration and moves to the next one.

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if (i == 5)
    continue;

You’ll use both in your number game.

Let’s Build the Multiplication Table Program

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using System;

class Program
{
    static void Main()
    {
        Console.WriteLine("Enter a number:");
        int num = Convert.ToInt32(Console.ReadLine());

        Console.WriteLine($"Multiplication Table of {num}");
        
        for (int i = 1; i <= 10; i++)
        {
            Console.WriteLine($"{num} x {i} = {num * i}");
        }
    }
}

Simple, clean, and powerful.

Now Add the Number Game

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Console.WriteLine("\nNumber Game:");

for (int i = 1; i <= 20; i++)
{
    if (i == 10)
        continue; // skip 10

    if (i == 15)
        break; // stop at 15

    Console.WriteLine(i);
}

This teaches true loop control, a must-have skill for all programmers.

How It Works

• for loop repeats the multiplication table steps
• continue skips printing number 10
• break stops the loop at 15
• Logic + repetition = smart programs

Run it in the DevsCall AI Online Runner to watch it work instantly.

Learn Together with AI

Try prompts like:

• “Create a loop that prints even numbers only.”
• “Rewrite this using while instead of for.”
• “Explain break vs continue in simpler words.”
• “Make a version that prints tables up to 20.”

AI becomes your personal loop tutor.

Practice Time

Write a program that:

1. Asks the user for a number
2. Prints all numbers from 1 to that number
3. Skips numbers divisible by 3
4. Stops completely if it reaches a number > 50

Expected output example:

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8
...
Stopped because number exceeded 50.

Example Solution

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using System;

class Program
{
    static void Main()
    {
        Console.WriteLine("Enter a limit:");
        int limit = Convert.ToInt32(Console.ReadLine());

        for (int i = 1; i <= limit; i++)
        {
            if (i > 50)
            {
                Console.WriteLine("Stopped because number exceeded 50.");
                break;
            }

            if (i % 3 == 0)
                continue;

            Console.WriteLine(i);
        }
    }
}

If your output matches, you’ve mastered loops!