Edsger Wybe Dijkstra (1930 -- 2002): A Portrait of a Genius

We discuss the scientific contributions of Edsger Wybe Dijkstra, his opinions and his legacy.Comment: 10 pages. To appear in Formal Aspects of Computin

Semantics of Separation-Logic Typing and Higher-order Frame Rules for<br> Algol-like Languages

We show how to give a coherent semantics to programs that are well-specified in a version of separation logic for a language with higher types: idealized algol extended with heaps (but with immutable stack variables). In particular, we provide simple sound rules for deriving higher-order frame rules, allowing for local reasoning

Development of an MSC language and compiler, volume 1

Higher order programming language and compiler for advanced computer software system to be used with manned space flights between 1972 and 198

GIER: A Danish computer from 1961 with a role in the modern revolution of astronomy

A Danish computer, GIER, from 1961 played a vital role in the development of a new method for astrometric measurement. This method, photon counting astrometry, ultimately led to two satellites with a significant role in the modern revolution of astronomy. A GIER was installed at the Hamburg Observatory in 1964 where it was used to implement the entirely new method for the measurement of stellar positions by means of a meridian circle, then the fundamental instrument of astrometry. An expedition to Perth in Western Australia with the instrument and the computer was a success. This method was also implemented in space in the first ever astrometric satellite Hipparcos launched by ESA in 1989. The Hipparcos results published in 1997 revolutionized astrometry with an impact in all branches of astronomy from the solar system and stellar structure to cosmic distances and the dynamics of the Milky Way. In turn, the results paved the way for a successor, the one million times more powerful Gaia astrometry satellite launched by ESA in 2013. Preparations for a Gaia successor in twenty years are making progress.Comment: 19 pages,8 figures, Accepted for publication in Nuncius Hamburgensis, Volume 2

A pascal compiler for PDP 11 minicomputers

In this paper the development of a cross-compiler running on the central computing facility is described. The compiler transforms PASCAL source code into object code for the PDP 11 family. The arguments for higher level languages on minicomputers and the choice made for PASCAL are discussed. It is shown that only a minor effort in terms of manpower is required if such a development is based on an existing compiler that is suited to the purpose of adaptation. Even without large amounts of optimization the code produced is both compact and efficient. Some attention is paid to requirements that should be fulfilled in portable compilers. The paper ends with a discussion of some strong points and weak points of the PDP 11 architecture

On the design of two small batch operating systems 1965 - 1970

This paper describes the design considerations and decisions for two small batch operating systems, called MICRO and MILLI, for the Electrologica X8, a Dutch computer delivered from 1965 onwards. Their sole tasks were to run sequences of ALGOL 60 programs, thus transforming the X8 into an ALGOL 60 computer. They were developed in order to increase the efficient use of the hardware (MICRO) and to reduce waiting times for ALGOL 60 programs with small demands (MILLI). The work described here was carried out mainly by one person, namely the author. The paper is interwoven with some personal history, describing a.o. the background and the context in which this work was carried out

Implications of Structured Programming for Machine Architecture

Based on an empirical study of more than 10,000 lines of program text written in a GOTO-less language, a machine architecture specifically designed for structured programs is proposed. Since assignment, CALL, RETURN, and IF statements together account for 93 percent of all executable statements, special care is given to ensure that these statements can be implemented efficiently. A highly compact instruction encoding scheme is presented, which can reduce program size by a factor of 3. Unlike a Huffman code, which utilizes variable length fields, this method uses only fixed length (1-byte) opcode and address fields. The most frequent instructions consist of a single 1-byte field. As a consequence, instruction decoding time is minimized, and the machine is efficient with respect to both space and time. © 1978, ACM. All rights reserved