TABLE OF CONTENTS The role of real-time software grows larger and larger, and in a competitive marketplace any marginal improvement in usability or performance, provided by more effective software, will give a significant sales advantage. This introductory chapter tries to outline the source of some of the problems which programmers and engineers are likely to encounter and provides a set of guidelines for identifying potential real-time systems by looking at a number of their characteristics. It also introduces associated key ideas through example applications which, at this early stage, may be more helpful than offering abstract principles.
Real-time processing normally requires both parallel activities and fast response. In fact, the term 'real-time' is often used synonymously with 'multi-tasking' or 'multi-threading', although this is not strictly correct: small real-time systems, as used in dedicated equipment controllers, can perform perfectly adequately with just a simple looping program. Indeed, the period I spent developing commercial embedded systems taught me that such simplicity of design has much merit, and with the massive increase in processor speeds, it is now possible to use such crude software schemes for a much wider range of applications. As long as the response is good enough, no further complexities need be introduced. But, if a large number of different inputs are being monitored by a single processor, or the input data streams are complex and structured, the simple polling loop approach will prove inflexible and slow, and a multi-tasking solution will be required. Whatever...
