Per Brinch Hansen (13 November 1938 – 31 July 2007) was a Danish-American computer scientist known for his work in operating systems, concurrent programming and parallel and distributed computing.

Biography

Early life and education

alt=Per Brinch Hansen as a student in 1959|thumb|Age 21 in 1959

Per Brinch Hansen was born in Frederiksberg, an enclave surrounded by Copenhagen, Denmark. His father, Jørgen Brinch Hansen, worked as a civil engineer, becoming a leading expert in soil mechanics, and later accepting a professorship at Technical University of Denmark. His mother, Elsebeth Brinch Hansen (née Ring), was the daughter of Danish composer Oluf Ring and worked as a hairdresser before marrying.

Brinch Hansen attended Skt. Jørgens Gymnasium and then studied electrical engineering at Technical University of Denmark where he sought an area to pursue that "was still in its pioneering phase" on the belief that "If a subject was being taught, it was probably already too late to make fundamental contributions." After a seven-week student internship at IBM's Hursley Laboratory in England, he decided to dedicate his career to computers. Initially focused on computer construction, reading a book on the IBM 7030 Stretch project that described computer organization from a programmer's point of view refocused his interest toward becoming a computer architect. Edsger Dijkstra had sent him to understand process synchronization using semaphores, and then implemented a specialized RC 4000 real-time monitor for use in managing a fertilizer plant. Peter Kraft and Charles Simonyi, who was still a teenager, wrote a p-code interpreter and data logging task programs that were compiled to p-code. By the spring of 1969, a well-documented, reliable version of the RC 4000 multiprogramming system was running.

California Institute of Technology

alt=Per Brinch Hansen at the Taj Mahal, after attending a conference in Bombay (1975)|thumb|At the Taj Mahal, after attending a conference in Bombay (1975)

In July 1972, Brinch Hansen joined the faculty of the California Institute of Technology (Caltech) as an Associate Professor of computer science, where he began work on defining a programming language with concurrent processes and monitors. In April 1974, he distributed a technical report on Concurrent Pascal. Subsequently, Brinch Hansen began writing model operating systems in Concurrent Pascal, to evaluate the language. In May 1975, he completed Solo, a single-user operating system for development of Concurrent Pascal programs. Next, he rewrote the original RC 4000 real-time scheduler in Concurrent Pascal, taking three days to write it, and three hours of machine time to systematically test it. In 1978, Brinch Hansen became the first computer scientist awarded the Doctor Technices degree, the highest academic distinction within engineering and technological science in Denmark, for the work documented in The Architecture of Concurrent Programs. Later in 1978, Brinch Hansen published the Distributed Processes language concept, proposing the use of remote procedure calls to synchronize processes running across a microcomputer network.

Also in 1978, L. J. Sevins and Steve Goings from Mostek visited Brinch Hansen at USC, where he outlined a low-cost multiprocessor architecture. Mostek began a project to implement such a multiprocessor, with Brinch Hansen working as a consultant. As with the RC 4000 project, Edison was also used as a formal specification language for the hardware. Mostek got an initial 4-node multiprocessor working and Brinch Hansen wrote a portable Edison compiler on a PDP 11/55, but shortly after, United Technologies acquired Mostek and cancelled the project. In 1982, Brinch Hansen moved the Edison system to an IBM Personal Computer (PC), and then published his third book, Programming a Personal Computer.

In 1982, Brinch Hansen was named the first Henry Salvatori Professor of Computer Science at USC.

While designing a multicomputer operating system for Danish company GN Elmi, Brinch Hansen concluded he needed a new language, this time leveraging the message passing paradigm of Hoare's CSP. Brinch Hansen developed a portable implementation on an IBM PC. with programs rewritten in SuperPascal, a fully implemented publication language he created for parallel algorithms.

Last years

In his later years, Brinch Hansen published a retrospective of his most important papers, The Search for Simplicity (1996), a text for a course in programming for non-majors, Programming for Everyone in Java (1999), a retrospective on the evolution of operating systems, Classic Operating Systems: From Batch Processing to Distributed Systems (2001), and a retrospective on the evolution of concurrent programming, The Origin of Concurrent Programming: From Semaphores to Remote Procedure Calls (2002). He self-published a 2004 memoir, A Programmer's Story: The Life of a Computer Pioneer, on his website.

On July 31, 2007, Brinch Hansen died, shortly after being diagnosed with terminal cancer.

Personal life

Brinch Hansen met his wife Milena (née Hrastar) on a class trip to Yugoslavia in 1962. They married in 1965 and had two children, daughter Mette and son Thomas. and his commitment to testing concepts in working systems – Brinch Hansen implemented and distributed working systems for new concepts he developed, noting:

Operating systems

The RC 4000 multiprogramming system introduced the now-standard concept of an operating system kernel and the separation of mechanism and policy in operating system design. Modern microkernel architectures trace their roots to the extensible nucleus architecture of the RC 4000. It is now available from the ACM Digital Library.

Using Concurrent Pascal, Brinch Hansen demonstrated that it was feasible to fully implement operating systems in high level languages, and that doing so reduced the development effort by one to two orders of magnitude. Furthermore, entire operating systems could be published, and understood in their entirety. Brinch Hansen did precisely that in The Architecture of Concurrent Programs, leading Roy Maddux and Harlan Mills to declare:

Concurrent programming

Brinch Hansen and Hoare developed the monitor concept. Brinch Hansen published the first monitor notation, adopting the class concept of Simula 67, Hoare refined the rules of process resumption. Brinch Hansen created the first implementation of monitors, in Concurrent Pascal. More than a dozen additional monitor-based languages had been created by 1990: Simone, Modula, CSP/k, CCNPascal, PLY, Pascal Plus, Mesa, SB-Mod, Concurrent Euclid, Pascalc, Concurrent C, Emerald, Real-time Euclid, Pascal-FC, Turing Plus, Predula. high-level facilities for concurrency, where the system could guarantee that processes access disjoint sets of variables only and do not interfere with each other in time dependent ways.

Source and portable code for Concurrent Pascal and the Solo operating system were distributed to at least 75 companies and 100 universities in 21 countries, resulting in its widespread adoption, porting and adaptation in both industry and academia.

In his 1978 paper on distributed processes, Brinch Hansen proposed a language for distributed computing based on external requests consisting of procedure calls between processes. This later became known in an operating system context as the remote procedure call.

Later, Brinch Hansen developed two languages extending Hoare's CSP message-passing paradigm with parallel recursion,

Honors and awards

  • Doctor Technices, Technical University of Denmark, for The Architecture of Concurrent Programs, 1978
  • First Henry Salvatori Professor of Computer Science, University of Southern California, 1982
  • IEEE Fellow, 1985
  • Distinguished Professor, Syracuse University, 1987
  • Chancellor's Medal, Syracuse University, 1989
  • IEEE Computer Pioneer Award, for pioneering development in operating systems and concurrent programming exemplified by work on the RC 4000 multiprogramming system, monitors, and Concurrent Pascal, 2002

Programming languages

  • Concurrent Pascal (1975)
  • Distributed Processes (1978)
  • Edison (1981)
  • Joyce (1987)
  • SuperPascal (1993)

Quotations

  • Writing is a rigorous test of simplicity: It is just not possible to write convincingly about ideas that cannot be understood