Hi Nasir,

Probably you have an old motherboard. Nowadays all the motherboard support "bidirectional" parallel ports.

there is a simple test. Run the PC in DOS mode and go to debug.

output a byte to the parallel port (whatever the address you have selected for the port)

Then read back the port.

If its the same data read in what you had outputted then its not bidirectional.

In a bidirectional parallel port you should get 0xffh (or perhaps 0x00h) if you read back.

Try setting your parallel port in different modes.

By the way what are you trying to do.


Babar