NAME
  Screen Image Arrays and Compatibility

DESCRIPTION
  Use bits-per-pixel-per-plane and planes values to determine the required size
  of the array that holds a graphics screen image. Bits-per-pixel-per-plane and
  planes values, along with the horizontal resolution, also determine which
  screen modes are compatibile:

                                                                   Horizontal
                                      Bits-per-pixel-              resolution
      Screen mode                     per-plane          Planes    (in pixels)
      ----------------------------    ---------------    ------    -----------
      1                               2                  1         320
      2, 4, 11                        1                  1         640
      3                               1                  1         720
      7                               1                  4         320
      8, 9(> 64K video memory), 12    1                  4         640
      9(64K video memory), 10         1                  2         640
      13                              8                  1         320

  The following formula gives the required size, in bytes, of an array used
  to hold a captured image:

  size% = 4 + INT(((PMAP (x2!, 0) - PMAP (x1!, 0) + 1) *
          (bits-per-pixel-per-plane%) + 7) / 8) * planes% *
          (PMAP (y2!, 1) - PMAP (y1!, 1) + 1)

  GET and PUT operations are compatible in screen modes with the same
  horizontal resolution and bits-per-pixel-per-plane and planes values. For
  example, screen modes 2, 4, and 11 are compatible, and screen modes 8 and 12
  are compatible.

SEE ALSO
  SCREEN Statement Screen Modes