The main links with your PC and the outside world are the centronic port, used for connecting the printer, the RS232 port, used for the mouse, and the games port for a joystick. This book explores how these input/output (I/O) ports can be put to use through a range of other interfacing applications. This is especially useful for laptop and palmtop PCs which cannot be fitted with internal I/O cards. A novel approach is taken by this book, combining the hardware through which the ports can be explored, and the software programming needed to carry out a range of experiments. Circuits are provided.