---
title: Doing Math
---

# #10. Doing Math

<div class="ui segment note">
<span class="ui ribbon label">Note</span>
This is a web-version of a tutorial chapter embedded right into the XOD IDE.
To get a better learning experience we recommend to install the
<a href="/downloads/">desktop IDE</a> or start the
<a href="/ide/">browser-based IDE</a>, and you’ll see the same tutorial there.
</div>

You probably noticed that pins have different colors.

The pin’s color indicates the *type* of data that this pin is compatible with.
Green pins can take and return numerical values. Blue pins work with pulses, a
special data type that we will return to later.

Let’s try to do some math.

![Patch](./patch.png)

As you can guess, the `multiply` node transfers the result of the multiplication
of the numbers from the `X` and `Y` pins to the `PROD` pin.

In `xod/core`, you will find nodes for different mathematical and trigonometric
calculations. Along with the `multiply` node, you will find `add`, `subtract`,
and `divide` for very basic computations.

## Test circuit

<div class="ui segment note">
<span class="ui ribbon label">Note</span>
The circuit is the same as for the previous lesson.
</div>

![Circuit](./circuit.fz.png)

[↓ Download as a Fritzing project](./circuit.fzz)

## How-to

1. Add a new `multiply` or another math node to the patch.
2. Link its `X` input to the first value provider.
3. Set the `Y` input value with the Inspector or link it to an output too.

![Screencast](./screencast.gif)

Turn the potentiometer knob. If you have followed the example. The LED on port
11 will reach the maximum brightness with a half-turn of the knob. This happens
because the `multiply` node multiplied the values of `X` and `Y`, and
transferred them to the `PROD` pin. As `Y` was set to 2 in the Inspector, the
value of the `pot` node doubles before reaching the `LUM` pin of LED2.

[Next lesson →](../11-servo/)