%N tvzoom %F $MIR/src/subs/tv.for
%D Zoom a region of an image on a TV device.
%P jm
%: tv, display
%B
      subroutine tvzoom(zoom, xc, yc)
      implicit none
      integer zoom, xc, yc

  Input:
    zoom    Integer zoom value.
    xc      Integer position of the desired X center of expansion.
    yc      Integer position of the desired Y center of expansion.

            range for zoom is 1 (no zoom) to MAXZOOM (typically 16).
            ranges for xc and yc are as follows:
              (1 <= xc <= MAXTVX) and (1 <= yc <= MAXTVY) with
              xc = 1 at the LHS and yc = 1 at the bottom of the TV
              (MAXTVX and MAXTVY are found with TvChar).

  Output:
    None
