A chapter on real-time control shows how to write programs that trigger on external events, such as a signal transition at the parallel port or time or calendar information. There's a discussion and examples of using the parallel port as the power source for low-power external circuits. The proper cable can mean the difference between a link that works reliably and one that doesn't. This book shows how to choose an appropriate parallel-port cable, and how to design the circuits that interface to the cable. Although the parallel port was originally intended as an interface between a PC and a printer or other peripheral, it's also become a popular interface for transferring information between two PCs.
Every programmer has a favorite language.
For the program examples in this book, I wanted to use a popular language so as many readers as possible could use the examples directly, and this prompted my decision to use Microsoft's Visual Basic for Windows. A big reason for Visual Basic's popularity is that the programming environment makes it extremely easy to add controls and displays that enable users to control a program and view the results. However, this book isn't a tutorial on Visual Basic. It assumes you have a basic understanding of the language and how to create and debug a Visual-Basic program. I developed the examples originally using Visual Basic Version 3, then ported them to Version 4.