The ZDecimal command makes the following changes to the window variables:
Because of the dimensions of the graph screen (95 by 63, when you remember that the last row and column aren't used), this has the useful effect that every pixel has round X- and Y-coordinates with at most one decimal digit. Also, the screen has correct proportions: a specific distance in the X direction is the same number of pixels in length as the same distance in the Y direction. This makes the window dimensions created by ZDecimal a friendly window (the ZInteger and ZSquare commands also have this effect, but in slightly different ways)
Using the ZDecimal command prevents gaps in certain graphs, and makes sure vertical asymptotes with integer coordinates are graphed correctly. Also, circles will be drawn as actual circles with this graphing window(unlike other windows, with which they might appear stretched).
The values given for Xmin, Xmax, etc. above are only correct for the Full mode setting (which is the default, and the most common setting). In Horiz and G-T modes, the values will be different, preserving the property that two pixels next to each other differ in coordinates by 0.1:
- Ymin= -1.5 and Ymax= 1.5 in Horiz mode (Xmin and Xmax are the same)
- Ymin= -2.5 and Ymax= 2.5 in G-T mode, while Xmin= -2.3 and Xmax= 2.3
- ERR:INVALID occurs if this command is used outside a program.