I have used the parallel port from QBASIC.  I basically agree with what

Ken wrote but will add a couple of comments

Hex 378 is the usual address for a modern computer's LPT1

from QBasic you can use OUT with either hex or decimal arguments but
hex arguments must be preceded by &h eg OUT(&h378,255) would write all
ones to the data bits of (usually) LPT1

As far as I know you can do this with the all the non NT based versions

of windows as they give direct access to their ports.  I have used
win95.

When reading from the ports it can be necessary to write either zero or

one to each bit (or is it to set each line high or low - see next note)

first, I can't remember which.

some of the bits are inverted on the output lines.

A desktop Output will have enough current to drive LED but not enough
to blow.

A laptop will not supply enough to drive LED.

You can get this sort of information through a google search.

Alan

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