The Pascal programming language creator Niklaus Wirth reflects on its origin, spread, and further development.
Niklaus Wirth
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Microprocessor architectures: a comparison based on code generation by compiler
By carefully tuning computer and compiler, it is possible to avoid the otherwise inevitable compromises between complex compiling algorithms and less-than-optimal compiled code, where the key to performance appears to lie neither in sophisticated nor drastically reduced architectures, but in the key concepts of regularity and completeness.
From programming language design to computer construction
From NELIAC (via ALGOL 60) to Euler and ALGOL W, to Pascal and Modula-2, and ultimately Lilith, Wirth's search for an appropriate formalism for systems programming yields intriguing insights and surprising results.
Program development by stepwise refinement
The creative activity of programming—to be distinguished from coding—is usually taught by examples serving to exhibit certain techniques. It is here considered as a sequence of design decisions concerning the decomposition of tasks into subtasks and of data into data structures. The process of successive refinement of specifications is illustrated by a short but nontrivial example, from which a number of conclusions are drawn regarding the art and the instruction of programming.
What can we do about the unnecessary diversity of notation for syntactic definitions?
The population of programming languages is steadily growing, and there is no end of this growth in sight. Many language definitions appear in journals, many are found in technical reports, and perhaps an even greater number remains confined to proprietory circles. After frequent exposure to these definitions, one cannot fail to notice the lack of “common denominators.” The only widely accepted fact is that the language structure is defined by a syntax. But even notation for syntactic description eludes any commonly agreed standard form, although the underlying ancestor is invariably the Backus-Naur Form of the Algol 60 report. As variations are often only slight, they become annoying for their very lack of an apparent motivation.
Toward a discipline of real-time programming
Programming is divided into three major categories with increasing complexity of reasoning in program validation: sequential programming, multiprogramming, and real-time programming. By adhering to a strict programming discipline and by using a suitable high-level language molded after this discipline, the complexity of reasoning about concurrency and execution time constraints may be drastically reduced. This may be the only practical way to make real-time systems analytically verifiable and ultimately reliable. A possible discipline is outlined and expressed in terms of the language Modula.
On multiprogramming, machine coding, and computer organization
The author feels that the interrupt feature which is available in most modern computers is a potent source of programming pitfalls and errors, and that it therefore may heavily contribute to the unreliability of programs making use of it. A programming scheme is presented which avoids the concept of the interrupt and permits the specification of concurrent (or pseudoconcurrent) activities in a supposedly more perspicuous manner. It is intended to serve as a basis for the construction of operating systems, which are prime examples of programs with concurrent activities. The scheme includes a set of basic instructions for the generation, termination, and synchronization of parallel processes. A set of routines representing these instructions and thereby simulating a hypothetical machine organization has been implemented and tested on the IBM System/360. Two programs using these instructions, written in PL360, are presented.
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