Computer languages, like natural languages, evolve. For regulated languages, changes are consolidated into distinct versions at well-defined points in time. For Ada, the main versions have been Ada 83, Ada 95 and now Ada 2005. Whereas Ada 95 was a significantly different language from its ancestor, Ada 2005 is more an upgrade. It brings Ada up to date with respect to current practice in other languages, operating systems and theory – especially in the real-time domain.

Although Ada is a general purpose programming language, much of its development has been driven by the requirements of particular application areas. Specifically, the needs of high-integrity and safety-critical systems, real-time systems, embedded systems and large complex long-life systems. To support this wide range of applications, Ada has a large number of language features and primitives that can be grouped into the following:

• strong typing with safe pointer operations,

• object-oriented programming support via tagged types and interfaces,

• hierarchical libraries and separate compilation,

• exception handling,

• annexes to give support to particular application domains,

• low-level programming features that enable device drivers and interrupt handlers to be written,

• an expressive concurrency model and

• an extensive collection of entities that support real-time systems programming.

This book has concentrated on the last three items in this list to provide a comprehensive description of real-time and concurrent programming. These are two of the unquestionable strengths of the Ada language.