For Loop Explanations

Why do we need a loop?

Suppose I want the servo motor to move from 0° to 180°.

I could write:

myServo.write(0);
myServo.write(1);
myServo.write(2);
...
myServo.write(180);

But that would mean writing more than 180 lines of code!

Instead, we use a for loop, which allows us to repeat the same instructions automatically.

Look at this code:

for (int angle = 0; angle <= 180; angle++) {
    myServo.write(angle);
    delay(15);
}

A for loop has three parts:

for (initialization; condition; increment)

Let’s understand each part.

Part 1: Initialization

int angle = 0

Here, I create a variable called angle and give it a starting value of 0.

So, the servo starts from 0 degrees.

Part 2: Condition

angle <= 180

This means:

Continue repeating as long as the angle is less than or equal to 180.

Part 3: Increment

angle++

This means:

Increase the value of angle by 1 after every repetition.

It is the same as:

angle = angle + 1;

First time through the loop

angle = 0

So,

myServo.write(0);

The servo moves to 0°.

Second time

angle = 1

So,

myServo.write(1);

The servo moves to 1°.

Third time

angle = 2

So,

myServo.write(2);

The servo moves to 2°.

This continues:

0°
1°
2°
3°
...
180°

When the angle becomes 181,

181 <= 180

is false.

So the loop stops.

Now look at the second loop:

for (int angle = 180; angle >= 0; angle--) {
    myServo.write(angle);
    delay(15);
}

Here,

• We start from 180.
• Continue as long as the angle is greater than or equal to 0.
• Decrease the angle by 1 every time.

angle--

means

angle = angle - 1;

So the servo moves like this:

180°
179°
178°
...
2°
1°
0°

Remember this:

for (int angle = 0; angle <= 180; angle++)

means:

Start from 0, continue until 180, and increase by 1 each time.

And

for (int angle = 180; angle >= 0; angle--)

means:

Start from 180, continue until 0, and decrease by 1 each time.

One-line definition:

A for loop is used when we know how many times we want to repeat a set of instructions.