Simula - History

History

The following account is based on Jan Rune Holmevik's historical essay.

Kristen Nygaard started writing computer simulation programs in 1957. Nygaard saw a need for a better way to describe the heterogeneity and the operation of a system. To go further with his ideas on a formal computer language for describing a system, Nygaard realized that he needed someone with more programming skills than he had. Ole-Johan Dahl joined him on his work January 1962. The decision of linking the language up to ALGOL 60 was made shortly after. By May 1962 the main concepts for a simulation language were set. "SIMULA I" was born, a special purpose programming language for simulating discrete event systems.

Kristen Nygaard was invited to UNIVAC late May 1962 in connection with the marketing of their new UNIVAC 1107 computer. At that visit Nygaard presented the ideas of Simula to Robert Bemer, the director of systems programming at Univac. Bemer was a sworn ALGOL fan and found the Simula project compelling. Bemer was also chairing a session at the second international conference on information processing hosted by IFIP. He invited Nygaard, who presented the paper "SIMULA -- An Extension of ALGOL to the Description of Discrete-Event Networks".

Norwegian Computing Center got a UNIVAC 1107 August 1963 at a considerable discount, on which Dahl implemented the SIMULA I under contract with UNIVAC. The implementation was based on the UNIVAC ALGOL 60 compiler. SIMULA I was fully operational on the UNIVAC 1107 by January 1965. In the following couple of years Dahl and Nygaard spent a lot of time teaching Simula. Simula spread to several countries around the world and SIMULA I was later implemented on Burroughs B5500 computers and the Russian URAL-16 computer.

In 1966 C. A. R. Hoare introduced the concept of record class construct, which Dahl and Nygaard extended with the concept of prefixing and other features to meet their requirements for a generalized process concept. Dahl and Nygaard presented their paper on Class and Subclass Declarations at the IFIP Working Conference on simulation languages in Oslo, May 1967. This paper became the first formal definition of Simula 67. In June 1967 a conference was held to standardize the language and initiate a number of implementations. Dahl proposed to unify the type and the class concept. This led to serious discussions, and the proposal was rejected by the board. SIMULA 67 was formally standardized on the first meeting of the SIMULA Standards Group (SSG) in February 1968.

Simula was influential in the development of Smalltalk and later object-oriented programming languages. It also helped inspire the Actor model of concurrent computation although Simula only supports co-routines and not true concurrency.

In the late sixties and the early seventies there were four main implementations of Simula:

• UNIVAC 1100 by NCC
• System/360 and System/370 by Swedish Research Institute for National Defence (FOA)
• CDC 3000 by University of Oslo's Joint Computer Installation at Kjeller
• TOPS-10 by ENEA AB

These implementations were ported to a wide range of platforms. The TOPS-10 implemented the concept of public, protected, and private member variables and methods, that later was integrated into Simula 87. Simula 87 is the latest standard and is ported to a wide range of platforms. There are mainly three implementations:

• Simula AS
• Lund Simula
• GNU Cim

In November 2001 Dahl and Nygaard were awarded the IEEE John von Neumann Medal by the Institute of Electrical and Electronic Engineers "For the introduction of the concepts underlying object-oriented programming through the design and implementation of SIMULA 67". In February 2002 they received the 2001 A. M. Turing Award by the Association for Computing Machinery (ACM), with the citation: "For ideas fundamental to the emergence of object oriented programming, through their design of the programming languages Simula I and Simula 67." Unfortunately neither Dahl, nor Nygaard could make it to the ACM Turing Award Lecture, scheduled to be delivered at the OOPSLA 2002 conference in Seattle, as they both died within two months of each other] in June and August, respectively.

Simula Research Laboratory is a research institute named after the Simula language, and Nygaard held a part time position there from the opening in 2001.

The new Institute of Computer Science (Institutt for Informatikk) at the University of Oslo is named Ole Johan Dahl's House, after one of the two inventors of Simula. The main auditorium in Ole Johan Dahl's House is named Simula.

Simula is still used for various types of university courses, for instance, Jarek Sklenar teaches Simula to students at University of Malta.