Introducing Ada 95
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Sample Chapter From Introducing Ada95
Copyright © John Barnes
1 Evolution of Ada 95
Ada is a modern programming language suitable for those application areas which benefit from the discipline of organized development, that is, Software Engineering ; it is a general purpose language with special applicability to real-time and embedded systems. Ada was originally developed by an international design team in response to requirements issued by the United States Department of Defense [DoD 78].
1.1 The Revision Process
Although Ada was originally designed to provide a single flexible yet portable language for real-time embedded systems to meet the needs of the US DoD, its domain of application has expanded to include many other areas, such as large-scale information systems, distributed systems, scientific computation, and systems programming. Furthermore, its user base has expanded to include all major defense agencies of the Western world, the whole of the aerospace community and increasingly many areas in civil and private sectors such as telecommunications, process control and monitoring systems. Indeed, the expansion in the civil sector is such that civil applications now generate the dominant revenues of many vendors.
1.2 The Requirements
The development of the requirements was a somewhat iterative process with a number of sub-phases. First, the community of users was invited to submit Revision Requests, secondly, these were sorted and analyzed in order to determine what was really implied by the requests, and finally, a coherent set of requirements was written.
1.3 The Main User Needs
The Requirements reflected a number of underlying User Needs which had become apparent over the years since Ada was first defined. Apart from a small number of very specific matters such as the character set issue, the specialized areas and generally tidying up minor inconsistencies, four main areas stood out as needing attention:
1.4 The Approach
In responding to the revision requirements, the Revision team followed the inspiration of Jean Ichbiah (who led the original design team), both in remaining faithful to the principles underlying the original Ada design, and in the approach to the revision process. To quote Dr Ichbiah in his introduction to John Barnes' textbook on Ada [Barnes 82]:
1.5 Using this Document
This document provides a description of the main features of Ada 95 and the rationale for the changes from Ada 83. It follows the inspiration of the rationale for Ada 83 [IBFW 86] by blending exposition with explanation.