The original IBM-PC's Parallel Printer Port had a total of 12 digital outputs and 5 digital inputs accessed via 3 consecutive 8-bit ports in the processor's I/O space.
Various enhanced versions of the original specification have been introduced over the years
so now the original is commonly referred to as the
Introduction Programming Considerations Registers and Pinouts
Reading and Writing Data How many ports are present and where
last updated: 26-Jan-98 Ian Harries <ih@doc.ic.ac.uk>