The earth, viewed through the window of an airplane, shows a regularity and reptition of features, for example, hills, valleys, rivers, lakes, and forests. Nevertheless, there is great local variation; Vermont does not look like Utah. Similarly, if we rise above the details of a few programming languages, we can discern features that are common to many languages. This is the programming language landscape; the main features include variables, types, control structures, and input/output. Again, there is local variation; Pascal does not look like Basic. This work is a broad and comprehensive discussion of the principal features of the major programming languages. A Study of Concepts The text surveys the landscape of programming languages and its features. Each chapter concentrates on a single language concept. A simple model of the feature, expressed as a mini-language, is presented. This allows us to study an issue in depth and relative isolation. Each chapter concludes with a discussion of the way in which the concept is incorporated into some well-known languages. This permits a reasonably complete coverage of language issues.

If Charles Babbage is to be regarded as the father of modern day computer technology, then surely the Countess Augusta Ada Lovelace, after whom this new language is named, must be remembered as its midwife. It was she, the daughter of England's poet Lord Byron, who translated the work of the Italian mathematician L.F. Menabrea, attaching her own scientific commentaries on the dissimilarities between the difference engine and the analytical engine. It was Lady Lovelace, the great lady of computers, who delivered the notes and loosely organized writings of Babbage, with her own invaluable amendments, to a world not quite ready to receive them. The Ada language effort has employed hundreds, if not thousands, of minds and a healthy sum of money since its conception. Ada was fostered by the High Order Language Working Group (HOLWG), chartered by the U.S. Department of Defense in January of 1975 with the overall objective of developing a systematic approach to improved use of software by the military. One would think the Pentagon an unlikely foster parent for a new computer language. Regardless of its lineage, the question that begs asking is, of course - Why? The answer is by no means a simple one, but some brief background may help to clarify the matter. At present, the Department of Defense is the largest software consumer on earth, employing roughly 400 different computer languages and dialects. The situation, some have commented, is at best untidy.