Nygaard, who presented the paper "SIMULA – An Extension of ALGOL to the Description of Discrete-Event Networks". The Norwegian Computing Center got a UNIVAC 1107 in 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 few 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 other computers including the Burroughs B5500 and the Russian Ural-16. 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 coroutines and not true concurrency. In the late sixties and the early seventies, there were four main implementations of Simula: UNIVAC 1100 by Norwegian Computing Center (NCC) System/360 and System/370 by NCC CDC 3000 by University of Oslo's Joint Computer Installation at Kjeller TOPS-10 by Swedish National Defence Research Institute (FOA) These implementations were ported to a wide range of platforms. The TOPS-10 implemented the concept of public, protected, and private member variables and procedures, 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 four implementations: Simula AS Lund Simula GNU Cim Portable Simula Revisited In November 2001, Dahl and Nygaard were awarded the IEEE John von Neumann Medal by the Institute of Electrical and Electronics Engineers "For the introduction of the concepts underlying object-oriented programming