BIOS / Int / Int 10 / 04


            INT 10 - VIDEO - READ LIGHT PEN POSITION (all but PS)

Input		Output
AX	04h	Switch		AX
BX		Pixel Column		BX
CX		Raster Line (CH for old Modes)		CX
DX		Row (Y)	Column (X)	DX
ES:DI		Destroyed		SP,BP,SI,DI

Switch: 0 = Light Pen Switch not activated (other returns undefined)
        1 = Light Pen Switch activated (other returns are valid)