Real time forth

This book has been written to provide information about using a computer with the real world so the two may work cooperatively together. In many situations in which a computer is used, the main constraint is getting the job done, usually as quickly as possible. The exact time each part of the task takes is not of great significance and the job proceeds with timing to suit, and dictated by, the computer. Interfacing the computer with the outside world requires things to be done at precisely the times the outside world demands. Often many things (tasks) must be done, if not together, in an interleaved way so that one task is not kept waiting to start until all other tasks have fully finished. Data will need to be taken as and when available, output will need to be passed on at the times and in the form the outside world needs it. This is why there is 'Real Time' in the title. Why Forth? This book is intended for use as a teaching text, either in a formal situation or for self study. The only way to learn is to first read and then to do. This requires that a language suitable for the task be chosen. Forth is used as the language for interfacing for a number of good reasons. It is fast, especially when run on hardware designed for the language, but fast enough even when run on general purpose equipment. It is interactive, providing an environment in which immediate testing as you go clarifies the task in hand and helps catch errors early so they can be painlessly corrected. It is a rich, structured language that provides facilities useful for interfacing that are missing in many other languages. [Introduction]