# What’s a Function?

## Operators

An “operator” in a program looks like your Math book:

5 + 10 # Addition 10 - 5 # Subtraction 21 * 2 # Multiplication 21 / 7 # Division

## What about Square Roots?

We don’t have a symbol for square root.

Our keyboards are pretty limited.

My first computer could only display 127 characters

## Functions!

- Has a name
- Usually has an “input”
- Returns an “output”

```
sqrt(36)
```

(sqrt 36)