A Programmer's Story. The Life Of A Computer Pioneer
A PROGRAMMER’S STORYThe Life of a Computer PioneerPER BRINCH HANSEN
FOR CHARLES HAYDENc 2004 by Per Brinch Hansen.Copyright All rights reserved.Per Brinch Hansen5070 Pine Valley Drive, Fayetteville, NY 13066, USA
CONTENTS1AcknowledgmentsvLearning to Read and Write 1938–571Nobody ever writes two books – My parents – Hitler occupiesDenmark – Talking in kindergarten – A visionary teacher – Theclass newspaper – “The topic” – An elite high school – Variety ofteachers – Chemical experiments – Playing tennis with a champion– Listening to jazz – “Ulysses” and other novels.217Choosing a Career 1957–63Advice from a professor – Technical University of Denmark –Ørsted’s influence – Distant professors – Easter brew – Fired forbeing late – International exchange student – Masers and lasers– Radio talk — Graduation trip to Yugoslavia – An attractivetourist guide – Master of Science – Professional goals.3Learning from the Masters 1963–6635Regnecentralen – Algol 60 – Peter Naur and Jørn Jensen – Daskand Gier Algol – The mysterious Cobol 61 report – I join thecompiler group – Playing roulette at Marienlyst resort – Jumpstarting Siemens Cobol at Mogenstrup Inn – Negotiating salary –Compiler testing in Munich – Naur and Dijkstra smile in Stockholm – The Cobol compiler is finished – Milena and I are marriedin Slovenia.4Young Man in a Hurry 1966–7059Naur’s vision of datalogy – Architect of the RC 4000 computer –Programming a real-time system – Working with Henning Isaksson, Peter Kraft, and Charles Simonyi – Edsger Dijkstra’s influence – Head of software development – Risking my future at HotelMarina – The RC 4000 multiprogramming system – I meet EdsgerDijkstra, Niklaus Wirth, and Tony Hoare – The genius of NielsIvar Bech.581Shaping a New Field 1970–72Alan Perlis invites me to spend a year at Carnegie-Mellon – Emigration to America – Niklaus Wirth defines Pascal – Driving homein a blizzard – Discussing the future of concurrent programmingin Marktoberdorf and Belfast – Alan Perlis tells stories – MadKing Ludwig and Thomas Edison – The first modern book onOperating System Principles.iii
ivContents6Inventing the Future 1972–76103Can you tell me, what is Caltech? – Sunshine and palm trees inFebruary – Wine-tasting with the dean – Driving across America –A question of priority – Two baffling problems – That sounds easy– Concurrent Pascal and Solo – Al Hartmann’s compiler – The artof compromise – Getting a sore throat in Bombay – Returning toMarktoberdorf – The distraction of grants – Leaving the magickingdom – A passion for clear thinking.7The End of an Era 1976–84The legendary Zohrab Kaprielian – Football game at the RoseBowl – Creating a top department at USC – How Harvard grantstenure – The first book on concurrent programming – Doctor technices – Surviving the executive vice president – Designing theEdison multiprocessor for Mostek – United Technologies kills theproject – Let no man complain to me – Brush fire and mud slidesin Altadena – Magical simplicity – What we achieved.1318Danish Interlude 1984–87Student democracy and teaching in Denmark – Danish industryuses Concurrent Pascal – Consulting for GN Corporation – Rocking the boat.1539Back in America 1987–2004Distinguished professor at Syracuse – Birthday celebration in theformer Danish West Indies – Becoming an American citizen – Parallel scientific computing – A personal supercomputer – Parallelcryptography – History of programming languages – The Computer Pioneer Award – Final words.163Sources181Index189
ACKNOWLEDGMENTSFor helpful comments on my story, I thank Len Adleman, Birger Andersen, SvenEriksen, Jon Fellows, Nissim Francez, Steve Goings, Sol Golomb, Christian Gram,Jonathan Greenfield, Al Hartmann, Nils Havsteen, Charles Hayden, Niels ZeuthenHeidam, Giorgio Ingargiola, Henning Isaksson, Konrad Jahn, Jørn Jensen, AnitaJones, Peter Kraft, Paul Lindgreen, Aage Melbye, Peter Naur, Børge Ring, CharlesSimonyi, Leif Svalgaard, Fred Thompson, Villy Toft, Peter Villemoes, Paul Waltenburg, and Bill Wulf.My special thanks go to Charles Hayden, who helped me publish this book onthe internet, and Jim Horning, who read all the chapters. And to Børge Ring fortranslating excerpts from a Dutch trip report by Edsger Dijkstra.I am grateful for permission to quote from the following material:The personal letters of Jonathan Fellows, Steve Goings, Al Hartmann, Charles Hayden,Jim Horning, Giorgio Ingargiola, Anil Menon, Villy Toft, Niklaus Wirth, and TomZepko.Klasseavisen (“The class newspaper”) 1945–45, Konrad Jahn’s class at Niels EbbesensvejSchool, Frederiksberg, Denmark. (Excerpts translated from Danish by Per BrinchHansen.)E. W. Dijkstra, EWD316A, Reisverslag van Edsger W. Dijkstra aan Summer School,c 1971 by Maria C. Dijkstra-Debets. (ExcerptsMarktoberdorf, juli 1971 (in Dutch). translated from Dutch by Børge Ring and Per Brinch Hansen.)R. A. Maddux and H. D. Mills, Review of Per Brinch Hansen: The Architecture of Conc 1979 IEEE.current Programs. IEEE Computer 12, (May 1979), 102–103. P. Naur, Review of Per Brinch Hansen: Operating System Principles. BIT 15, 1975,c 1975 by BIT.455–457. P. Naur, Notes for the official defense of Per Brinch Hansen’s Dr. technices thesis at theTechnical University of Denmark, January 23, 1978. (Excerpts translated from Danishby Per Brinch Hansen.)P. Naur, Unpublished review of Per Brinch Hansen: Programming a Personal Computer,1984.A. J. Perlis, Talk on “Computing in the fifties.” ACM National Conference. Nashville,TN, 1981. Transcript in J. A. N. Lee (ed.), Computer Pioneers, IEEE Computerc 1995 IEEE.Society Press, Los Alamito, CA, 1995, 545–556. PER BRINCH HANSENSyracuse Universityv
1LEARNING TO READ AND WRITE 1938–57Nobody ever writes two books – My parents – Hitler occupies Denmark – Talkingin kindergarten – A visionary teacher – The class newspaper – “The topic” – Anelite high school – Variety of teachers – Chemical experiments – Playing tennis witha champion – Listening to jazz – “Ulysses” and other novels.Walking home from a Caltech party in the 1970s, I told Don Knuth thatI was working on my second book. He turned to me and said “Nobodyever writes two books!” I should know—this is is my tenth book. It tellsthe story of my professional life and my impressions of the birth of modernprogramming with anecdotes about software pioneers I have known.As a student of electrical engineering, I dreamt of making fundamentalcontributions to a new field. In 1963, I graduated from the Technical University of Denmark without any programming experience—it was not yetbeing taught. There were, as far as I remember, no textbooks available onprogramming languages, compilers or operating systems. That was my mainreason for choosing to work in computing!Over the next forty years I worked as a systems programmer in Denmarkand a computer scientist in America. I witnessed computer programmingchange from an amateur activity into something resembling an engineering discipline, and was fortunate to contribute to the early development ofoperating systems and concurrent programming.In this autobiography, I trace my school years, engineering studies, andthe beginning of my career in Denmark. And I recount my exciting and frustrating years as a researcher at Carnegie-Mellon, Caltech, USC, Universityof Copenhagen, and Syracuse University.I wrote the book for fun. I assume you know how to use a computerand are interested in programming. My story is mostly told in nontechnicaldetail. In a few places, where the story gets a bit technical, I explain thegist of the ideas.c 2004 by Per Brinch Hansen.Copyright 1
2A Programmer’s Story?You may well wonder why I describe my school days in a book about myprofessional life. Well, over the years, I have learned that, besides intellect,the most valuable asset of a programmer is the ability to write clearly. Needless to say, I wasn’t born with a talent for writing well. But, thanks to myteachers, I learned to write nontrivial essays in elementary school throughhigh school.Now, if you don’t write really well when you graduate from high school,you probably never will. Since I consider my writing skills to be far moreimportant than my engineering background, I will begin my story by tellingyou how I learned to read and write.After half a century, the memories of my childhood and youth are naturally somewhat fragmentary. And, like your life, mine did not follow acoherent script. I must also confess that some of my more “random” impressions are included simply because I find them amusing—as I hope youwill too.My parents, Jørgen Brinch Hansen and Elsebeth (née Ring), lived inFrederiksberg, a suburb of Copenhagen, Denmark. I was born on November 13, 1938, and nicknamed “Busser” after a popular cartoon character.(Americans know him as Blondie’s husband Dagwood.)My mother was the daughter of the Danish composer Oluf Ring. Shewas a charming, vivacious woman with a beautiful smile. Before marryingmy father she worked in one of the best hairdressing salons in Copenhagen.On pictures from my childhood she is always well dressed and, even on thebeach, her hairstyle looks perfect. When I was little, she liked to go shoppingin the center of Copenhagen with me dressed in my best. I would ratherhave stayed at home playing with friends, but that was not an option.When the neighbors complained about me (as they often did) my motherwould try to hide it from my father. This was, however, impossible on theoccasion when I threw a cobblestone through a basement window acrossthe street. What a lovely sound that was! When my father heard about it(and the repair costs) he spanked me and sent me to bed without dinner.When that happened, my mother would usually sneak a sandwich into mybedroom.People liked my mother and found her fun to be with. In her forties shevisited Italy with her sister and brother-in-law. At an outdoor theater inRome, some tourists were relaxing in front of an empty stage. My motherimmediately walked up on the stage and danced across it to the applause of
1. Learning to Read and Write 1938–573the audience.My mother smoked constantly. Even when she was cooking, she held acigarette in her mouth and tilted her head to avoid getting smoke in hereyes.She also had a taste for strong coffee. I once offered to demonstrate tomy graduate student, Jon Fellows, how coffee was meant to taste. First Imade a portion of normal (weak) American coffee. After letting the coffeedrip through a second portion of ground coffee, Jon and I enjoyed a cup ofreal Danish coffee. The next day he told me that his heart beat so fast hehad to lie down at home.My father was a tall, handsome man. On pictures he often looks stern andunsmiling. He was very intelligent, but rather silent. His mother died whenhe was only nine years old. His father then married a woman who talkedincessantly. She left my father with a distaste for small talk. I suspect heoften made people feel uncomfortable.In 1935, he graduated in civil engineering from the Technical Universityof Denmark. My father apparently found one class a waste of his time.Paperback editions of Danish textbooks had to be cut open, page by page,before you could read them. At his oral exam in Road Construction, myfather showed his disdain for the subject by bringing an uncut (unread)version of the professor’s textbook to the examination table. The professorrewarded him with the extremely low grade of mdl . This reduced myfather’s total grade point average on his diploma from ug– to mg . (TheDanish grades, ug–, mg , and mdl , correspond roughly to A–, B , andD– in America.)For twenty years, he worked for Christiani & Nielsen, a Danish engineering company that built harbors, docks, bridges, tunnels, airports, roads andrailways all over the world. One of his first tasks was to design proceduresfor lowering nine tunnel elements to the bottom of the river Maas in Rotterdam, one of Europe’s most heavily trafficked waterways. At the time it wasthe longest underwater tunnel in Europe. Each tunnel element, weighing15,000 tons, was 180 feet long, 75 feet wide and 27 feet tall.In May 1940, the German army invaded Holland. When the last tunnelpiece had been lowered in December 1940, my father returned home on oneof the last commercial flights from Rotterdam. The flight must have beensomewhat unnerving: the Germans had painted the cabin windows white toprevent the passengers from discovering military secrets from the air.After the war, my father became recognized as one of the world’s leading
4A Programmer’s Storyexperts in soil mechanics. In 1953, he was promoted to chief engineer atthe C&N headquarters in Copenhagen. Two years later he accepted a professorship in Soil Mechanics and Foundation Engineering at the TechnicalUniversity of Denmark.A Norwegian colleague wrote:In several respects Brinch Hansen’s personality was governed byhis consistency and his requirement for a logical and rationalapproach to all problems. This gave him an appearance whichcould easily be interpreted by outsiders as reserved superiority.On the contrary, those who knew him learned to appreciate hisability to discuss frankly the facts in any problem and also hisloyal and honest character. (Bjerrum 1969)I vividly remember when my father asked his driving instructor to demonstrate parallel parking. My father thought it would be most convenient to dothis on our street on a Sunday afternoon. So my parents ended up practicingthis difficult maneuver right in front of our neighbors and their kids. I canonly imagine what my mother must have thought.If my father thought something made sense, he never hesitated to take anunpopular stand. Once he invited me to attend a talk at the Danish Academyof Engineering. After the talk, the members voted on some proposal. Whilemy father voted against it, everybody else voted for it.After a stormy marriage, my parents separated when I was sixteen yearsold. This was a great tragedy for my mother who still loved him and neverhad a relationship with another man. She provided a stable, loving home formy sister and me, until she died on December 7, 1962, at age 50, a monthbefore I finished my engineering studies. My father died on May 27, 1969 atage 60, the year before I emigrated to the United States.My books on The Architecture of Concurrent Programs (1977) and Studies in Computational Science (1995) are dedicated to my parents.?On April 9, 1940, Hitler invaded Denmark. As a sixteen-month old child,I watched German bombers circling low above the rooftops of Copenhagendropping leaflets. Since Hitler’s real target was Norway, the leaflets lookedas if the Germans were trying to save money by writing in a mixture ofDanish and Norwegian.
1. Learning to Read and Write 1938–575The German occupation did not play a major role in my early childhood.It was, after all, the only life I knew until I was seven years old. But thewar years were not so easy for my parents. Most everyday necessities wererationed, including food, clothing, soap, and tobacco. There was a severeshortage of fuel for electricity, heating and transportation. The Germansimposed a curfew which forced people to stay overnight when they visitedfriends and relatives in the evening.I remember a couple of violent episodes on our street. One day, a manwas shot in front of me. The next day, I watched a street sweeper sweep alarge pool of blood into the gutter. It was rumored that the victim was shotsimultaneously from opposite ends of the street (which could not possiblyhave been true, unless the assassins were suicidal). On another occasion,a man was killed when Nazis blew up his villa in the middle of the nightacross the street from our apartment building. I believe he was a memberof the resistance movement. After the war, an apartment complex, built inhis garden, was named Bomhoffs Have in his memory.Although the Germans inflicted more inhumane suffering on other countries, many lives were lost in Denmark. During the occupation, the Germansexecuted a hundred saboteurs, and sent 150 communists and 500 Jews toconcentration camps. However, the Danes helped close to 7,000 Jews escapeto Sweden on small fishing boats.The war ended on May 4, 1945, when the German forces in Denmarkcapitulated to Fieldmarshal Montgomery. Had the Russians reached theDanish border before the English Army did, my life would have been verydifferent.?In 1944, at age 6, I went to Miss Hansen’s kindergarten on Lykkesholms Allein Frederiksberg. She had her own way of keeping 33 little kids reasonablyquiet. If you talked too much, you were placed on a tall chair during thelunch break facing the other children with your mouth covered by a towel.It doesn’t seem to have worked in my case. I still talk too much instead oflistening.I don’t remember if we learned the alphabet in kindergarten. But I havean early memory of crying in frustration, while my mother helped me tellthe difference between the letters h and k.?
6A Programmer’s StoryOn September 1, 1945, I began my elementary education at Niels Ebbesensvej school in Frederiksberg in a class of 39 boys. For the next five years,we had the same teacher in all subjects. His name was Konrad Jahn. He wasthe most important teacher in my life. The second week of class he promisedthat we would publish a weekly newspaper, as soon as we were able to writestories.Two years later Mr. Jahn wrote:About five months later, we were able to publish the first issueof the Class Newspaper, which I immodestly believe is the firstschool paper written, typed, and duplicated by [Danish] kids inthe first grade. . .By putting the greatest emphasis on TeachingIndependence, the children have now in the middle of the thirdgrade reached the point where they produce the paper completelyon their own.Here are a few stories from the class newspaper (dates are shown in theAmerican abbreviated style—month/day/year):– I destroyed the class newspaper, for I forgot to remove the pencil [frominside the stencil]. So Mr. Jahn had to retype the whole paper. (PerJust Sørensen, 1st grade, 6/12/1946)– On Mondays we give talks, and on Fridays we also give talks. Wealso watch a movie about how an engine makes a car drive, and thenMr. Jahn asks for questions, and then one of us asked how one makesa cow glare! (Eskild Sørensen, 2nd grade, 1/20/1947)– Nearly every day, Per Brinch is late. And I really believe he wouldlike a chauffeur to drive him to school, And he also has an electricalarmclock, and every day when he has to go to school, a wire is looseor a tooth wheel is broken, and then he is full of stories and alwayshas a letter about the alarmclock, the wires, and his parents . . . In themorning when the alarm clock rings very softly, he wakes up, and thenhe is too lazy to get up. (Peter, 2nd grade, 4/12/1947)– Yesterday we heard a talk in the basement and there were even slidesshown. And Per Brinch stood and pointed at tunnel elements allthe way across the river so the cars can drive underwater. (ErikMichaelsen, 3rd grade, 1/8/1948)
1. Learning to Read and Write 1938–577– On Easter Monday, I sat down at my uncle’s desk to write a letter tomy father and mother. Then two days later I come back to the desk,and the letter is still there (because there was no stamp on it). Theday before I went home I go back in there, and it was still lying there.So I threw it in the wastepaper basket. (Per Brinch, 4th grade, 1949)In the fourth grade each of us had to write a report on how a newspaperis produced, from the moment a journalist writes a story until the printednewspaper is distributed. After visiting the newspaper Berlingske Tidende,we read about The Topic (as Jahn called it), and cut pictures out of oldnewspapers. The class newspaper shows that we spent 14 hours on thisproject per week. I won the first prize of two kroner (roughly, a quarter)for my final report of 60 handwritten pages with 50 illustrations. Thanks toMr. Jahn, I had written my first substantial report when I
2 A Programmer’s Story You may well wonder why I describe my school days in a book about my professional life. Well, over the years, I have learned that, besides intellect, the most valuable asset of a programmer is the ability to write clearly.Need-
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Le genou de Lucy. Odile Jacob. 1999. Coppens Y. Pré-textes. L’homme préhistorique en morceaux. Eds Odile Jacob. 2011. Costentin J., Delaveau P. Café, thé, chocolat, les bons effets sur le cerveau et pour le corps. Editions Odile Jacob. 2010. Crawford M., Marsh D. The driving force : food in human evolution and the future.
Le genou de Lucy. Odile Jacob. 1999. Coppens Y. Pré-textes. L’homme préhistorique en morceaux. Eds Odile Jacob. 2011. Costentin J., Delaveau P. Café, thé, chocolat, les bons effets sur le cerveau et pour le corps. Editions Odile Jacob. 2010. 3 Crawford M., Marsh D. The driving force : food in human evolution and the future.
