Loops in C++: For, While and Do-While

Imagine you’re practicing free throws in basketball. You don’t take just one shot, you repeat the motion again and again: 1, 2, 3… maybe 50 times.
Repeating an action is part of learning, and computers also repeat actions using loops.

In this lesson, you’ll teach C++ how to repeat tasks automatically, counting, adding numbers, printing patterns, without writing the same line again and again.

Simple Counting Machine

You’ll build a small program that prints a counting sequence from 1 to 10.

Here’s what it should look like:

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========================
   COUNTING PROGRAM
   1 2 3 4 5 6 7 8 9 10
========================

Instead of writing ten print statements, you’ll use a loop to make C++ do the work for you.

Why Loops Important

Loops repeat actions automatically.
They save time, reduce code, and allow programs to handle large tasks easily.

The for Loop

Use a for loop when you know exactly how many times you want to repeat an action.
Perfect for counting, fixed repetitions, and printing sequences.

Example

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for (int i = 1; i <= 10; i++) {
    cout << i << " ";
}

Explanation:
Starts at 1, repeats until 10, increasing by 1 each time.

The while Loop

Use while when you want to repeat something as long as a condition is true.
You don't always know how many repetitions you’ll need.

Example

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int i = 1;
while (i <= 10) {
    cout << i << " ";
    i++;
}

Explanation:
Keeps printing numbers while i is less than or equal to 10.

The do-while Loop

A do-while loop runs at least once, even if the condition is false.
Useful for menus and user-driven programs.

Example

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int i = 1;
do {
    cout << i << " ";
    i++;
} while (i <= 10);

Explanation:
Code inside do { } runs first, then the condition is checked.

break

Stops the loop immediately. Useful when you want to exit early.

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for (int i = 1; i <= 10; i++) {
    if (i == 5) break;
    cout << i << " ";
}

Explanation:
Stops printing when i reaches 5.

continue

Skips one loop step and moves to the next.

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for (int i = 1; i <= 10; i++) {
    if (i == 5) continue;
    cout << i << " ";
}

Explanation:
Prints all numbers except 5.

Counting

Loops can generate sequences like 1 to 10 or 10 to 1.

Summation

Add a series of numbers easily using loops.

Example

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int sum = 0;
for (int i = 1; i <= 5; i++) {
    sum += i;
}

Patterns

Loops can print shapes, lines, triangles, grids.

Simple star pattern

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for (int i = 1; i <= 5; i++) {
    cout << "* ";
}

Let’s Build It: Counting Program

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#include <iostream>
using namespace std;

int main() {
    cout << "========================" << endl;
    cout << "   COUNTING PROGRAM" << endl;

    for (int i = 1; i <= 10; i++) {
        cout << i << " ";
    }

    cout << endl << "========================" << endl;
    return 0;
}

How It Works

• The for loop starts at 1 and repeats until 10.
• Each iteration prints the current value of i.
• The output appears in a single clean line.

You can test this instantly using the DevsCall AI Code Runner.

Learn Together with AI

Try giving your AI Copilot commands like:

• “Create a loop in C++ that prints numbers from 1 to 50.”
• “Show me how to use while loops for summation.”
• “Write a pattern that prints a 5×5 square of stars.”

AI can rewrite, fix, or expand your loops instantly.

Practice Time

Write a C++ program that prints this pattern using a for loop:

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========================
   STAR LINE
   * * * * * * * * * *
========================

Your program must:

• Use a loop, not ten print statements.
• Print exactly 10 stars with spaces.
• Format the output exactly as shown.

If you need help, ask AI:

“How do I print stars using a loop in C++?”