Niklaus Wirth

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.

An axiomatic definition of the programming language PASCAL

SummaryThe axiomatic definition method proposed in reference [5] is extended and applied to define the meaning of the programming language PASCAL [1]. The whole language is covered with the exception of real arithmetic and go to statements.

The programming language pascal

SummaryA programming language called Pascal is described which was developed on the basis ofAlgol 60. Compared toAlgol 60, its range of applicability is considerably increased due to a variety of data structuring facilities. In view of its intended usage both as a convenient basis to teach programming and as an efficient tool to write large programs, emphasis was placed on keeping the number of fundamental concepts reasonably small, on a simple and systematic language structure, and on efficient implementability. A one-pass compiler has been constructed for the CDC 6000 computer family; it is expressed entirely in terms of Pascal itself.

EULER: a generalization of ALGOL, and its formal definition: Part II

In this section the algorithmic language EULER is described first informally and then formally by its syntax and semantics. An attempt has been made to generalize and extend some of the concepts of ALGOL, thus creating a language which is simpler and yet more flexible than ALGOL 60. A second objective in developing this language was to show that a useful programming language which can be processed with reasonable efficiency can be defined in rigorous formality.

The programming language Oberon

This is the defining report of the programming language Oberon.

The programming language Pascal

SummaryA programming language called Pascal is described which was developed on the basis ofAlgol 60. Compared toAlgol 60, its range of applicability is considerably increased due to a variety of data structuring facilities. In view of its intended usage both as a convenient basis to teach programming and as an efficient tool to write large programs, emphasis was placed on keeping the number of fundamental concepts reasonably small, on a simple and systematic language structure, and on efficient implementability. A one-pass compiler has been constructed for the CDC 6000 computer family; it is expressed entirely in terms of Pascal itself.

The Programming Language Ada Reference Manual

Lexical elements.- Declarations and types.- Names and expressions.- Statements.- Subprograms.- Packages.- Visibility rules.- Tasks.- Program structure and compilation issues.- Exceptions.- Generic units.- Representation clauses and implementation-dependent features.- Input-output.

PL360, a Programming Language for the 360 Computers

A programming language for the IBM 360 computers and aspects of its implementation are described. The language, called PL360, provides the facilities of a symbolic machine language, but displays a structure defined by a recursive syntax. PL360 was designed to improve the readability of programs which must take into account specific characteristics and limitations of a particular computer. It represents an attempt to further the state of the art of programming by encouraging and even forcing the programmer to improve his style of exposition and his principles and discipline in program organization. Because of its inherent simplicity, the language is particularly well suited for tutorial purposes. The attempt to present a computer as a systematically organized entity is also hoped to be of interest to designers of future computers.

On the Composition of Well-Structured Programs

In diesem Artikel beschreibt Niklaus Wirth im Wesentlichen, was strukturierte Programmierung bedeutet und wieso sie der rein Performance-orientierten Programmierung vorzuziehen sei. Als Ausgangspunkt nimmt er die rasante Entwicklung von Computern. Bis Anfang der 60er Jahre war es laut Wirth noch notwendig, alle denkbaren Programmiertricks anzuwenden, um die Maschinen bis an ihre Grenzen der Leistungsfahigkeit zu bringen. Damals waren die Programme noch nicht so umfangreich, dass dieser unubersichtliche Programmier-Stil zum Problem wurde. Mit der Zeit wurden aber die Computer leistungsfahiger, so dass auch die Moglichkeiten wuchsen und die Probleme zunehmend komplexer wurden. Die Leistungsoptimierung wurde zunehmend unbedeutender, wahrend die Fehlerbehandlung der durch strukturlose Programmier-Methoden sehr unuberschaubaren Programme immer mehr Zeit in Anspruch nahm. Als Losung nennt Niklaus Wirth die wohlstrukturierte Programmierung.

The design of a pascal compiler

The development of a compiler for the programming language PASCAL1 is described in some detail. Design decisions concerning the layout of program and data, the organization of the compiler including its syntax analyser, and the over‐all approach to the project are discussed. The compiler is written in its own language and was implemented for the CDC 6000 computer family. The reader is expected to be familiar with Reference 1.