> For the complete documentation index, see [llms.txt](https://docs.revrobotics.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.revrobotics.com/rev-professional-development-technical-path/blocks-boot-camp/variables.md).
# Introduction to Variables
## What is a Variable?
In math, it's common to see problems like below:
$$
a + 8 = 15
$$
We can solve for "a" to determine a = 7, right? Then we could solve a variety of additional calculations with that knowledge like:
$$
a + 10 = ?
$$
$$
2a = ?
$$
$$
34/a = ?
$$
**Variables** in programming serve the same role! We use a variable to represent a value, or other information, that then can be used throughout the program.
### Why use a Variable?
Consider for a moment: Why would we use a variable when we could simply use the number on its own?
While there are several reasons, one of the biggest is that variables can greatly help with organization in a program and streamline making changes.
Rather than having to hunt down every place a value has been used in a program, if we need to make a change we can adjust just the variable and be done! This helps to prevent mismatches that could come from one value being updated, but another missed.
An example of a variable used in multiple places
Variables might also be used to store the results of a calculation in a program to then be used wherever it's needed, such as the values from joystick movements on the gamepad.
### Types of Variables
**Constant variables** do not change after being set. These are often set during initialization or at the start of an OpMode.
Example of Constant Variables in Blocks
These variables might include something like a target velocity, position, or power that will be reused or other settings that need to remain consistent whenever called.
**Non-constant variables** are often just called variables. These change throughout the program, but may be set during initialization or the beginning of an OpMode to a default.
These variables, for example, may store the results of a calculation run in the OpMode or data collected by a sensor.
