Contributor: SWAG SUPPORT TEAM In the old days writing to ports on your computer was easy; all you had to do was use the port[ n ] command. Delphi no longer supports the port[ n ] command, so you have to use functions like: function ReadPortB( wPort : Word ) : Byte; begin asm mov dx, wPort in al, dx mov result, al end; end; procedure WritePortB( wPort : Word; bValue : Byte ); begin asm mov dx, wPort mov al, bValue out dx, al end; end; Of course, your operating system may not let you write to certain ports, specially if you're running on Windows NT.