The predefined local variable height is used in Mode7 windows, and it is assigned to each process. It is therefore only relevant in the coordinate system of mode7 (Ctype=C_M7). It is used to define the height of the process graphics in relation to the semi-3d field. This is not to be confused with the local variable Z, as that is used to control the depth of the graphical layers.
The height is normally a positive number, because the height of the bottom is 0, and all the processes are placed above it. When the height variable is not defined, it is 0 by default. The graphic base is placed at the indicated height, with the exception when controlpoint number 0 is changed (the default is overruled by the Center_set() function). In that case, the controlpoint will be placed at that height.