Ole-Johan Dahl (12 October 1931 – 29 June 2002) was a Norwegian

computer scientist A computer scientist is a person who is trained in the academic study of computer science. Computer scientists typically work on the theoretical side of computation, as opposed to the hardware side on which computer engineers mainly focus (al ...

. Dahl was a professor of computer science at the

University of Oslo The University of Oslo ( no, Universitetet i Oslo; la, Universitas Osloensis) is a public research university located in Oslo, Norway. It is the highest ranked and oldest university in Norway. It is consistently ranked among the top universit ...

and is considered to be one of the fathers of

Simula Simula is the name of two simulation programming languages, Simula I and Simula 67, developed in the 1960s at the Norwegian Computing Center in Oslo, by Ole-Johan Dahl and Kristen Nygaard. Syntactically, it is an approximate superset of ALGOL 6 ...

and

object-oriented programming Object-oriented programming (OOP) is a programming paradigm based on the concept of "objects", which can contain data and code. The data is in the form of fields (often known as attributes or ''properties''), and the code is in the form of pr ...

along with

Kristen Nygaard Kristen Nygaard (27 August 1926 – 10 August 2002) was a Norwegian computer scientist, programming language pioneer, and politician. Internationally, Nygaard is acknowledged as the co-inventor of object-oriented programming and the programming ...

Career

Dahl was born in

Mandal, Norway Mandal is a List of towns and cities in Norway, town in Lindesnes municipality in Agder county, Norway. Mandal is the fourth largest town in Agder as well as the administrative centre of Lindesnes municipality. It is located at the mouth of the r ...

. He was the son of Finn Dahl (1898–1962) and Ingrid Othilie Kathinka Pedersen (1905–80). When he was seven, his family moved to

Drammen Drammen () is a city and municipality in Viken (county), Viken, Norway. The port and river city of Drammen is centrally located in the south-eastern and most populated part of Norway. Drammen municipality also includes smaller towns and village ...

. When he was thirteen, the whole family fled to Sweden during the

German occupation of Norway The occupation of Norway by Nazi Germany during the Second World War began on 9 April 1940 after Operation Weserübung. Conventional armed resistance to the German invasion ended on 10 June 1940, and Nazi Germany controlled Norway until the ...

World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...

. After the war's end, Dahl studied numerical

mathematics Mathematics is an area of knowledge that includes the topics of numbers, formulas and related structures, shapes and the spaces in which they are contained, and quantities and their changes. These topics are represented in modern mathematics ...

at the University of Oslo. Dahl became a full

professor Professor (commonly abbreviated as Prof.) is an Academy, academic rank at university, universities and other post-secondary education and research institutions in most countries. Literally, ''professor'' derives from Latin as a "person who pr ...

at the

in 1968 and was a gifted teacher as well as researcher. Here he worked on ''Hierarchical Program Structures'', probably his most influential publication, which appeared co-authored with C.A.R. Hoare in the influential book ''Structured Programming'' of 1972 by Dahl,

Edsger Dijkstra Edsger Wybe Dijkstra ( ; ; 11 May 1930 – 6 August 2002) was a Dutch computer scientist, programmer, software engineer, systems scientist, and science essayist. He received the 1972 Turing Award for fundamental contributions to developing progra ...

, and Hoare, perhaps the best-known academic book concerning software in the 1970s. As his career advanced, Dahl grew increasingly interested in the use of

formal methods In computer science, formal methods are mathematically rigorous techniques for the specification, development, and verification of software and hardware systems. The use of formal methods for software and hardware design is motivated by the expec ...

, to rigorously reason about object-orientation for example. His expertise ranged from the practical application of ideas to their formal mathematical underpinning to ensure the validity of the approach. Dahl is widely accepted as Norway's foremost computer scientist. With Kristen Nygaard, he produced the initial ideas for object-oriented (OO) programming in the 1960s at the

Norwegian Computing Center Norwegian Computing Center (NR, in Norwegian: ''Norsk Regnesentral'') is a private, independent, non-profit research foundation founded in 1952. NR carries out contract research and development in the areas of computing and quantitative methods for ...

(Norsk Regnesentral (NR)) as part of the

I (1961–1965) and Simula 67 (1965–1968)

simulation A simulation is the imitation of the operation of a real-world process or system over time. Simulations require the use of Conceptual model, models; the model represents the key characteristics or behaviors of the selected system or proc ...

programming language A programming language is a system of notation for writing computer programs. Most programming languages are text-based formal languages, but they may also be graphical. They are a kind of computer language. The description of a programming ...

s, which began as an extended variant and

superset In mathematics, set ''A'' is a subset of a set ''B'' if all elements of ''A'' are also elements of ''B''; ''B'' is then a superset of ''A''. It is possible for ''A'' and ''B'' to be equal; if they are unequal, then ''A'' is a proper subset of ...

ALGOL 60 ALGOL 60 (short for ''Algorithmic Language 1960'') is a member of the ALGOL family of computer programming languages. It followed on from ALGOL 58 which had introduced code blocks and the begin and end pairs for delimiting them, representing a k ...

. Dahl and Nygaard were the first to develop the concepts of

class Class or The Class may refer to: Common uses not otherwise categorized * Class (biology), a taxonomic rank * Class (knowledge representation), a collection of individuals or objects * Class (philosophy), an analytical concept used differentl ...

, subclass (allowing implicit

information hiding In computer science, information hiding is the principle of segregation of the ''design decisions'' in a computer program that are most likely to change, thus protecting other parts of the program from extensive modification if the design decisio ...

inheritance Inheritance is the practice of receiving private property, Title (property), titles, debts, entitlements, Privilege (law), privileges, rights, and Law of obligations, obligations upon the death of an individual. The rules of inheritance differ ...

dynamic object creation An object-oriented operating system is an operating system that is designed, structured, and operated using object-oriented programming principles. An object-oriented operating system is in contrast to an object-oriented user interface or programm ...

, etc., all important aspects of the OO paradigm. An ''object'' is a self-contained component (with a data structure and associated procedures or ''methods'') in a software system. These are combined to form a complete system. The object-oriented approach is now pervasive in modern

software development Software development is the process of conceiving, specifying, designing, programming, documenting, testing, and bug fixing involved in creating and maintaining applications, frameworks, or other software components. Software development invol ...

, including widely used imperative programming languages such as

C++ C++ (pronounced "C plus plus") is a high-level general-purpose programming language created by Danish computer scientist Bjarne Stroustrup as an extension of the C programming language, or "C with Classes". The language has expanded significan ...

and

Java Java (; id, Jawa, ; jv, ꦗꦮ; su, ) is one of the Greater Sunda Islands in Indonesia. It is bordered by the Indian Ocean to the south and the Java Sea to the north. With a population of 151.6 million people, Java is the world's List ...

. He received the

Turing Award The ACM A. M. Turing Award is an annual prize given by the Association for Computing Machinery (ACM) for contributions of lasting and major technical importance to computer science. It is generally recognized as the highest distinction in compu ...

for his work in 2001 (with

). He received the 2002

Institute of Electrical and Electronics Engineers The Institute of Electrical and Electronics Engineers (IEEE) is a 501(c)(3) professional association for electronic engineering and electrical engineering (and associated disciplines) with its corporate office in New York City and its operation ...

(IEEE)

John von Neumann Medal The IEEE John von Neumann Medal was established by the IEEE Board of Directors in 1990 and may be presented annually "for outstanding achievements in computer-related science and technology." The achievements may be theoretical, technological, or ...

(with Kristen Nygaard) and was named Commander of the

Royal Norwegian Order of St. Olav Royal may refer to: People * Royal (name), a list of people with either the surname or given name * A member of a royal family Places United States * Royal, Arkansas, an unincorporated community * Royal, Illinois, a village * Royal, Iowa, a ci ...

in 2000. The

Association Internationale pour les Technologies Objets Example The Association Internationale pour les Technologies Objets, also known as AITO, is a non-profit association to promote the advancement of research in object-oriented technology. Each year it awards the Dahl–Nygaard Prizes and beginning ...

named the Dahl-Nygaard Prize after Dahl.

Early papers

* * * * * * * * * * Organized by IFIP Technical Committee 2, programming languages; O.-J. Dahl, conference chairman. * *

References

Sources

* ''From Object-Orientation to Formal Methods: Essays in Memory of Ole-Johan Dahl'', Olaf Owe, Stein Krogdahl and Tom Lyche (eds.),

Springer Springer or springers may refer to: Publishers * Springer Science+Business Media, aka Springer International Publishing, a worldwide publishing group founded in 1842 in Germany formerly known as Springer-Verlag. ** Springer Nature, a multinationa ...

Lecture Notes in Computer Science ''Lecture Notes in Computer Science'' is a series of computer science books published by Springer Science+Business Media since 1973. Overview The series contains proceedings, post-proceedings, monographs, and Festschrifts. In addition, tutorials, ...

, Volume 2635, 2004. . . * Pioneer who Prepared the Ground for Road to Java, Jonathan Bowen. ''

The Times Higher Education Supplement ''Times Higher Education'' (''THE''), formerly ''The Times Higher Education Supplement'' (''The Thes''), is a British magazine reporting specifically on news and issues related to higher education. Ownership TPG Capital acquired TSL Education ...

'', 1677:34, 4 February 2005.

External links

Homepage – comprehensive amount of info, pictures, and biblio
{{DEFAULTSORT:Dahl, Ole-Johan 1931 births 2002 deaths People from Mandal, Norway University of Oslo alumni University of Oslo faculty Norwegian computer scientists Programming language designers Turing Award laureates Formal methods people Dahl–Nygaard Prize

Career

Early papers

See also

References

Sources

External links