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The PTYPE menu within 3D (IV) 
The PTYPE menu under 3D contains the following functions: 
 
 
 
These functions correspond to the graphics options Slopefield, Wireframe, Y-
Slice, Ps-Contour, Gridmap and Pr-Surface presented earlier in this chapter.   
Pressing one of these soft menu keys, while typing a program, will place the 
corresponding function call in the program.   Press L@)@3D@@ to get back to the 
main 3D menu. 
 
The VPAR menu within 3D (V) 
The variable VPAR stands for Volume PARameters, referring to a 
parallelepiped in space within which the three-dimensional graph of interest is 
constructed.   When press [VPAR] in the 3D menu, you will get the following 
functions.  Press L to move to the next menu: 
 
    
 
Next, we describe the meaning of these functions: 
 
INFO (S) and VPAR (W)
 
When you press @INFO (S) you get the information shown in the left-hand side 
screen shot above. The ranges in Xvol, Yvol, and Zvol describe the extent of 
the parallelepiped in space where the graph will be generated.  Xrng and 
Yrng describe the range of values of x and y, respectively, as independent 
variables in the x-y plane that will be used to generate functions of the form z 
= f(x,y). 
 
Press  L and @INFO (Y) to obtain the information in the right-hand side screen 
shot above. These are the value of the location of the viewpoint for the three-
dimensional graph (Xeye, Yeye, Zeye), and of the number of steps in x and y 
to generate a grid for surface plots.