In 1968 Hewlett-Packard introduced the 9100A calculator, a programmable reverse-polish notation (RPN) computing machine that could rapidly perform floating point, trigonometric and hyperbolic functions as well as vector and polar operations. It came with a built-in magnetic card reader/writer for program and data storage. It used a CRT (cathode ray tube) for display of three data registers.

Hewlett-Packard soon followed up with the 9100B, an enhanced version that provided several new features (see below). In brief:

9100A: 16 registers, 196 program steps
9100B: 32 registers, 392 program steps

I am very interested in acquiring 9100A/B calculators, peripherals, manuals and associated documentation. If you have anything related to these HP calculators, please drop me a line!

Congratulations, you have just become the proud owner of a new Hewlett-Packard 9100B Calculator. This calculator is a big brother to the successful Hewlett-Packard 9100A. The 9100B however, has several features which more than triple its computing power, these being:
  • A TWO PAGE memory allowing up to 392 program steps or 32 data storage registers.
  • A true SUBROUTINE capability permitting instant access to subroutines from any point in a program.
  • A convenient X ← () operator allowing rapid data recall to the X register.
  • A STEP PROGRAM "dual display" greatly simplifying program editing and modification.
    These scans are from the 1969 HP Catalog. Click on any image for a larger version.


    • 9101A Extended Memory

      Plugs into the 9100A or 9100B, adding 248 registers capable of storing 3472 additional program steps.

    • 9102A Calculator Buffer
    • 9106A Typewriter Coupler
    • 9107A Digitizer
    • 9120A Printer
    • 9125A X-Y Plotter
    • 9150A Display Monitor

      Large Screen Display, with a 17-inch diagonal cathode ray tube for use in classrooms or for display to any large group.

    • 9160A Optical Card Reader

      It inputs program steps or data to the calculator using cards marked with a soft lead pencil.

    • Hewlett-Packard Calculator Model 9100A Operating and Programming Manual
      Part no. 09100-90001

    • Hewlett-Packard Calculator Model 9100B Operating and Programming Manual
      Part no. 09100-90021

    • Hewlett-Packard Calculator Model 9100A Program Library
      Part no. 09100-90002

    • Hewlett-Packard Calculator Model 9100B Program Library
      Part no. 09100-90022

    • Hewlett-Packard Calculator Model 9100A/B Interfacing Manual
      Part no. 09100-90031, February 1970, 77 pp.

    • HP Calculator Models 9100A/B Service Manual
      Part no. 09100-90034, January 1971

    • HP Calculator Extended Memory Model 9101A Service Manual
      Part no. 09101-90000, September 1970

    • HP Calculator Extended Memory Model 9101A Operating Manual
      Part no. 09101-90001, July 1970

    • HP Calculator Extended Memory Model 9101A Program Library
      Part no. 09101-90002

    • HP Calculator Extended Memory Model 9101A Memory Maps
      Part no. 09101-90003

    • HP Calculator Buffer 9102A Operating and Service Manual
      Part no. 09102-90000, July 1970

    • HP Calculator Printer Model 9120A Service Manual
      Part no. 09102-90001, August 1970

    • HP Calculator Printer Model 9120A Operating Manual
      Part no. 09102-90002, October 1970

    • United States Patent 3,623,156

      Assigned to Hewlett-Packard, inventor Thomas E. Osborne. Filed May 26, 1969 and granted November 23, 1971. The patent has a total of 61 pages, including corrections, that describe the calculator's various modules and sequencing.

    • Hewlett-Packard Journal, September 1968

      Has four articles describing various aspects of the machine:
      • "A New Electronic Calculator with Computer-like Capabilities"
      • "Hardware Design of the Model 9100A Calculator"
      • "Internal Programming of the 9100A Calculator"
      • "How the Model 9100A Was Developed"

    • Hewlett-Packard Journal, October 1970

      "More Memory for Desktop Calculators"

    • Hewlett-Packard KEYBOARD, Winter 1970

      From the inside front cover:

      The HP KEYBOARD is published quarterly to make the latest programs and application ideas available to all HP 9100 calculator owners.

      Your programs, both of general interest and in specialized applications categories, will help to keep other calculator owners better informed and increase the efficiency with which the HP 9100 is utilized throughout the world. Please send your programs to the HP KEYBOARD editor.

    • Inventions of Opportunities: Matching Technology with Market Needs , Selections from the pages of the Hewlett-Packard Journal
      (c) 1983 by Hewlett-Packard Company
      ISBN 0-9612030-0-5

      Pages 127 through 144 reproduce five articles from Volume 20, Number 1 (September 1968) of the Hewlett-Packard Journal.

      This book also has three articles from Volume 23, Number 10 (June 1972) regarding the HP-35 and four articles from Volume 25, Number 9 (May 1974) covering the HP-65. It also has two articles on the HP-IB (now IEEE 488) interface bus from Volume 24, Number 2 (October 1972).

    • How It All Began: Hewlett-Packard's Loveland Facility , Kenneth Jensen
      (c) 1999 by Agilent Technologies
      ISBN 1-928656-02-1

      From page 71 and continuing:

      One of the most significant products ever designed and manufactured by Hewlett-Packard was introduced in March 1968. This was the 9100A Desktop Computing Calculator, the forerunner to the personal computer or PC. The 9100A was the first, totally self-contained programmable unit of its kind which could fit on a desk. It included a display with three registers and a magnetic card reader. An optional printer, which fit neatly on the top of the 9100A, was offered separately. The 9100A used a ten-layer, PC board ROM for its algorithms, including log and trig functions. Its volatile core memory used small ferrite rings through which were woven copper wires. The initial price of $4900 was rather steep, and it was later lowered to $4,400. The 9100A was about the size and weight of an IBM typewriter. This product represented a significant departure for the Loveland Division's existing line of measurement equipment.

      The 9100A's performance seems insignificant today with limited internal memory that stored only 196 steps. It was truly innovative for its time, however. The 9100A spawned an entire line of desktop calculators developed by the Calculator Products Division at Loveland under the direction of Tom Kelley. The Fort Collins Division was formed to carry on this product line.

      Development of the 9100A started in 1965 in Palo Alto when a physicist named McMillian approached HP with a small calculator he invented. Tom Osborne, another inventor, also approached HP with his own home-built calculator. The best features of the two products were combined, and Osborne was hired as a consultant to continue the development work in HP Labs. The original size of the product was reduced by the invention of a PC board ROM by Chuck Near. Once the product's design was found feasible, it was transferred to to the Loveland Division. Chuck Near came along with the product.

      Responding to the wish of Arthur C. Clarke, author of 2001: A Space Odyssey, he was presented a 9100A in April, 1970. The unit was given to Clarke by Barney Oliver, Director of HP Labs.

    • Computer Structures: Readings and Examples , G. Gordon Bell and Allen Newell
      (c) 1971 by McGraw-Hill, Inc.
      ISBN 07-004357-4

      Chapter 20, pages 243 to 256, is entitled The HP Model 9100A computing calculator, which is a compilation of three articles from the September 1968 issue of the Hewlett-Packard Journal.

      Good photographs and diagrams.

      You can view this chapter on-line here, although the pictures aren't so great.

    • Electronics World, September 1971

      An engineer by the name of Paul Asmus, from HP's Calculator Products Division, wrote an article espousing the virtues of the programmable calculator. Although not mentioned by name in the text, the 9100 does make several appearances in photos that accompany the article.

      I've scanned the article and converted it to HTML. You can read the entire article and see the photos by clicking here.

    • Introduction to Computers and Computer Science, Richard C. Dorf
      (c) 1972 by Boyd and Frasier Publishing Company
      ISBN 0-87835-025-X

      Pages 103 through 122 cover the 9100 in some detail, describing the representation schemes for fixed and floating point numbers and moving into programming concepts and instructions.

      (Note that the second edition does not have this section. It was replaced by a more generic discussion of programmable calculators, along with a picture of a Wang calculator and a caption describing the HP 9825A.)

    • Proceedings of the IEEE, March 1984

      This "special issue" devoted to personal computers contains an article entitled The Design and Development of a Family of Personal Computers for Engineers and Scientists authored by Gerald Nelson and William Hewlett.

      The article describes the 9100A and 9100B in a few paragraphs, and goes on to posit:

      Our intent for the 9100 products was very clear in our minds. We were a team of scientists and engineers who wanted to build personal computers for other scientists and engineers. In retrospect, it is interesting to consider to what degree the 9100A should be considered the first mass-produced personal computer. A technology assessment of personal computers was conducted for the National Science Foundation by a research team at the University of Southern California, Los Angeles. The report, issued in September of 1980, acknowledges that it is difficult exactly to define "personal computer," but gives definitions containing the following criteria:
      • small, stand-alone
      • general purpose
      • advanced microelectronics technology (microprocessor)
      • operated by a single individual, interactively
      • no requisite computer training
      • affordable by an individual or small group

      The report concludes: "the distinction of being the first mass-produced personal computer (PC) probably belongs to the ALTAIR 8800 marketed in late 1974 by the small Albuquerque-based firm, MITS, Inc." (The Altair 8800 was based on the Intel 8080 microprocessor which was first delivered in 1973.) The HP 9100 machines substantially satisfied the above criteria. Microprocessors, of course, were not used in the 9100 since they did not then exist. Those who would argue that the 9100 was too specialized to be considered the first personal computer would almost certainly agree that the distinction is merited by one of the subsequent 9800 Series computers that provided full algebraic language capability and still predated 1974.

      (The report to which the article refers is "Technical Assessment of Personal Computers," vols I, II, University of Southern California, Los Angeles, U.S. Department of Commerce NTIS, September 1980.)

    • The ANALYTICAL ENGINE, May 1995

      Volume 2, number 3 of the Journal of the Computer History Association of California (ISSN 1071-6351) has an interview beginning on page 8 with the late Dr. Bernard Oliver regarding, in part, the development of the HP 9100.

      The issue can be read here. A local copy is here.

    This is taken from an interview that Arthur C. Clarke gave in 2001:
    In the 1930s, I was fascinated when I saw Babbage's computer at the Science Museum in London. It was wonderfully exciting.

    In the 1960s, I was doing an interview and mentioned that I had just heard about the Hewlett-Packard 9100A, a calculator that had a keyboard like a small typewriter and a three-line display. It was really the forerunner of what we now think of as the desktop computer. Soon after the story appeared I got a letter from Barney Oliver, the famous vice president of engineering at HP, who said, "Arthur, there is a Father Christmas." A 9100A was on its way to me.

    I suppose that's what I was thinking of when I came up with the HAL 9000 computer. And for 30 years I have been trying to set the story straight about the name HAL coming from IBM with one letter added to each. That was pure coincidence. HAL stands for Heuristic Algorithmic computer.

    I think IBM rather liked the idea, though. They later gave me a nice ThinkPad. I wrote "3001" on it. I've since defected to Compaq. I use their LTE 5300 laptop, which is several years old but works fine. I also have a desktop that was assembled locally.

    Comments to Dan Veeneman

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    Last revised February 26, 2006