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6.1 Definition of the terminal and input surface

As for the output, it is necessary to declare the input terminal:

•       SUBROUTINE DEVICI(N, PARAM)
        INTEGER N, PARAM(2)
  

  selects input terminal   N as active terminal.

  PARAM is a supplementary parameter for the input terminal. For example, it can define the type of cursor that the user can move around on the screen (0, 1 or 2). When initializing with  by DEFDEV, DEVICI is automatically called.

The input surface employed to enter the coordinates is a priori distinct from the visualization surface. For example, a graphics table has, in general, different dimensions than those of the screen in use, and it is not always desirable to make them correspond exactly. This is the reason why FORTRAN 3D enables us to define, as for graphics output,a frame on the input surface and a mask in the corresponding user space.

•       SUBROUTINE FENTRI(XMIN, XMAX, YMIN, YMAX)
        REAL XMIN, XMAX, YMIN, YMAX
  

  defines a   frame on the input surface , with the coordinates of the lower left corner, (XMIN, YMIN), and those of the upper right corner, (XMAX, YMAX). It is quite frequent that the dimensions of FENTRI and FENTR2 are the same for reasons that will be revealed in the subroutines described in the following section. The coordinates are given in centimeters.

•       SUBROUTINE MASQUI(XMIN, XMAX, YMIN, YMAX)
        REAL XMIN, XMAX, YMIN, YMAX
  

  defines a  mask  in the user space corresponding to the frame defined by FENTRI. The lower left corner of the frame is given by (XMIN, YMIN) and the upper right corner by (XMAX, YMAX). Here also, as for subroutine MASQU2, the unit system selected for the mask depends on the user. It is quite frequent that the dimensions of MASQUI and MASQU2 are the same for reasons that will be revealed in the subroutines described in the following section.

Interrogation subroutines exist to help the user to adapt the dimensions of the masks and windows better.