Outside a program, the Zoom Out tool allows you to pick a point on the graph screen and change the graphing window to a larger one centered at that point. The Zoom Out command, used in a program, also changes the graphing window to a larger one, but doesn't let you pick a point -- it uses the center of the screen.
The variables XFact and YFact are used to determine how much the graphing window changes: the total width of the screen, Xmax-Xmin, is multiplied by XFact, and the total height, Ymax-Ymin, is multiplied by YFact. Because you can't store a value less than 1 to either of these variables, the screen is guaranteed to get no smaller.
Aside from Xmin, Xmax, Ymin, and Ymax, no window variables are modified by this command (although ΔX and ΔY change as they are defined).
- ERR:INVALID occurs if this command is used outside a program.
- ERR:ZOOM is thrown if an overflow occurs calculating the new window dimensions (the window is too big)