Outside a program, the Zoom In tool allows you to pick a point on the graph screen and change the graphing window to a smaller one centered at that point. The Zoom In command, used in a program, also changes the graphing window to a smaller 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 divided by XFact, and the total height, Ymax-Ymin, is divided by YFact. Because you can't store a value less than 1 to either of these variables, the screen is guaranteed to get no larger.
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:WINDOW RANGE is thrown if the window is zoomed in beyond the level of the calculator's precision.