Olivetti/Programma 101/Revive/LetterThorkilNaur 20120619 2255

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Restoring an Olivetti Programma 101 to life

Dear Sir,

My name is Thorkil Naur and my first program I wrote for an Olivetti Programma 101 in 1972. I have worked and played with computers ever since.

The background of this letter is this: A few years ago, I became a member of "Dansk Datahistorisk Forening" - "Danish Computer History Society" is perhaps the most suitable English translation. Myself and other members of that Society are considering bringing an Olivetti Programma 101 back to life. We have the machine:


But we have no technical documentation.

We have noticed that you display several technical manuals on your web site


where especially the "Olivetti Programma 101 Technical Manual" and the "Olivetti Programma 101 Electronic Calculator (P 101) Repair Guide" would appear to be useful. We would be extremely grateful if you would assist us, somehow, to get access to these documents.

That was the short story and our request. Then comes the longer story.

My first meeting with the Olivetti Programma 101 was in the first year of the 3-year Danish "Gymnasium" (high school) in the autumn of 1972 when I was 15 years old. My first program found integer values of a and b, given the value of c in the equation a*a + b*b = c*c. For example, if you entered c = 5, the pair a = 3 and b = 4 would be output. So all in all, not an entirely simple program, one that involved a double loop with conditional jumps and taking the integer part.

Later programs included solving polynomium equations of degree 2, 3 and 4, computing analytic functions (like trigonometric functions) using suitable series expansions, and finding the date of Easter Sunday for a given year, in addition to the use of the Programma 101 for school work, mainly computations related to practical physics experiments. Among my fellow pupils, we had a fierce competition, writing the shortest program for the Programma 101 for solving the quadratic equation. I seem to recall that 27 instructions was the record, but I am not sure.

Although I have saved, in other cases, much of the material for programs that I worked on over the years, my material for the Programma 101 has been lost: For some reason that I don't recall, I borrowed the material to a friend who later admitted that he had thrown it out.

Another noteworthy program that I wrote for the Programma 101 tabulated the values of the factorial function

 n! = 1*2*3* ... *(n-1)*n

to multiple precision, that is, several registers were used to store a single number. I don't recall the limit exactly, but somewhere near 60 or 70 seems likely. My brother, who went to a different school, was likewise exposed to an Olivetti Programma, some later model, whose exact identity he no longer recalls. But it definitely had greater capacity than the P 101 and I wrote a program for him to use on that machine and was able to compute n! for even larger values of n than I had been able to on the P 101.

Soon after becoming familiar with the P 101, sometime during Christmas 1972-1973, my father noted this interest and decided to extend my horizon a bit. I should tell you that my father is Peter Naur, well known for his work on Algol 60 (he edited the famous Algol 60 report), the GIER Algol compiler and many other subjects. See


In 2005, he received the ACM A.M. Turing award.

In any case, he showed me how to use Newton-Raphson iteration to solve cubic equations, he wrote a program doing that in GIER Algol and we ran the program on the GIER that was available to him as a professor of "datalogy" (the term which he coined for the subject that is more ordinarily known as "computer science") at the University of Copenhagen. Although I then went ahead and learned Algol and machine code for the GIER, I continued to use the Olivetti Programma 101 right up to the end of my high school days in the summer of 1975.

I continued to use the GIER at the University of Aarhus where I started my university education in 1975. I don't recall exactly when I ran my last program on that machine, but it must have been around 1980.

A few years ago, I learned of the "Danish Computer History Society" who, as one of its activities, had collected a large amount of older computers and related equipment. "Data archeology" was the term used by the members for these activities. See


One of the goals of the society is the establishment of a museum of older, danish computer equipment. That goal is rather distant presently, but in the meantime, the more active members of the society entertain themselves by playing with the old equipment, attempting to recover and preserve both physical equipment, programs and data, trying restore the old equipment to life. I originally approached the society, hoping to experience once again a running GIER machine. At the time, the society had several pieces of GIER machinery, but not a running specimen. However, last year, a dedicated group managed to get one of the GIERs running again, a truly glorious accomplishment. And one that I, of course, enjoyed very much, since I was then able to run my old programs (I have preserved several boxes of paper tape) on the real machine.

One day, browsing around in the Society collection, I stumbled upon a specimen of the wonderful Olivetti Programma 101. It was part of a collection of machinery that the Society had taken over from a group of Danish Banks, see


And, of course, the idea of making this machine run again immediately arose. I should mention that I am neither a mechanical nor an electrical engineer, but I have competent members of the society that help me. And one of them mentioned that it would be, as I have noted earlier, extremely useful to have available some of the technical documentation for the P 101.

Hence my letter. I hope that I have not wasted too much of your time. And that you may spend some time responding, one way or the other. In any case, I am excited to communicate with you who seem to be, as I am, a great fan of the fabulous Olivetti Programma 101.

Hoping to hear from you, with great respect and best regards.

Thorkil Naur

Karen Brahes Vej 7, 2. t.v. DK-5000 Odense Danmark