HelpPC 2.10 Quick Reference Utility Copyright 1991 David Jurgens

                      INT 10,4 - Read Light Pen Position


       AH = 04


       on return:
       AH = 0  light pen switch not triggered
          = 1  light pen triggered
       BX = pixel column (0-319 or 0-639, mode dependent)
       CH = raster line (0-199) (CGA and EGA modes 4, 5 and 6)
       CX = raster line (EGA modes except 4, 5 and 6)
       DH = row (0-24)
       DL = column (0-79 or 0-79 mode dependent)


       - data returned as a byte coordinate, leaving horizontal
         accuracy to within 2 pixels (320) or 4 pixels (640)
       - vertical accuracy within 2 lines
       - PS/2's don't support the light pen interface

Esc or Alt-X to exit int 10,4 Home/PgUp/PgDn/End ←↑↓→