INT 33H 000dH: Enable Lightpen Emulation

 Expects: AX    000dH
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 Returns: none
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    Info: This causes the mouse support to work with programs which are
          written to support a light pen (e.g., using the PEN function on
          BASIC).  The mouse support apparently intercepts INT 10H 04H when
          this feature is enabled.

          When enabled, a click of either button is taken as a press of the
          pen button at current mouse position.

          Disable this support via INT 33H 000eH.

See Also: INT 33H: Mouse Support
          Interrupts and BIOS Services
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