floor is a mathematics primitive that reports the closest integer below a given number. In other words, it rounds the number down. For example, floor 5.2 would report 5, and floor -4.8 would report -5.

In the model example below, each turtle has a my-money variable that increases or decreases a little bit at each tick. We use the floor primitive to round up a turtle's my-money variable because we want to present a label under each turtle showing their current money. If we do not round this variable either up or down, their labels would show many floating point numbers such as 1.822882372836, which would be visually unpleasant. We also use the floor primitive in setting each turtle's ycor parameter so that the turtles move only when the rounded-up version of their my-money variable changes. If they make or lose just a little bit of money, they remain stationary. Lastly, we use the floor, and its opposite ceiling, for two of our three monitors in the interface.