Damage Calculation

I was looking over the damage calculation and part of the damage equation is the user's attack / defender's defense.
But there are moves like growl that lowers the enemy's def by 1. Is it possible to lower the defense to 0? If so then what would happen, as you cannot divide by 0.

Attack, defense (and their Special counterparts) and Speed can either be increased up to 6 stages, in .5 increments ( i.e 1.5x, 3x etc...) or decreased up to 6 stages which is the inverse of the increase such as 1/1.5 = .67 or 1/4 = .25. This makes the cap for decrease 0.25x and increase at 4x

Also Growl reduces Attack not Defense, maybe you?re thinking of Tail Whip or something?