This really depends on what your goals are. What
operating system, which port (serial, parallel, USB,
PCI, etc). Also, what language do you program in?
Easiest for parallel/serial port interfacing would
probably be using QBASIC under DOS. If using
Windows, easiest would probably be VB (MSComm
control for serial, Inpout32.dll for parallel port if
using WinXP).
This topic comes up over and over again, so doing
a search of the board should give you lots to read.
Nick