%N tvchar %F $MIR/src/subs/tv.for
%D Get characteristics of the display device.
%P jm
%: tv, display
%B
        subroutine TVchar(xmax,ymax,channels,levels)

        implicit none
        integer xmax,ymax,channels,levels

  This returns characteristics about the device we are using.

  The display device is assumed to be ``xmax'' by ``ymax'' pixels
  by ``channels'' images deep. Channels are number from 1 upwards
  to ``channels''.  The pixel coordinate system has pixel (1,1)
  in the lower left corner of the screen, and pixel (xmax,ymax)
  in the top right corner.

  Output:
    xmax,ymax  Screen size in pixels.
    channels   Number of image channels.
    levels     Number of grey scale levels.
