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Hewlett-Packard 9100A

Hewlett-Packard 9100A is a computer science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Hewlett-Packard 9100A rather than just read about it. In short: The Hewlett-Packard 9100A (HP 9100A) is an early programmable calculator (or computer), first appearing in 1968. HP called it a desktop calculator because, as Bill Hewlett said, "If we had called it a computer, it would have been rejected by our customers' computer gurus because it didn't look like an IBM.

Hewlett-Packard 9100A — main illustration
Hewlett-Packard 9100A — illustration

Key takeaways

  • Hewlett-Packard 9100A belongs to computer science; place it in that map before memorising details.
  • Learn the definition first, then one example that makes the definition concrete.
  • Connect Hewlett-Packard 9100A to a quantity you can measure, compute or draw — that is where exam questions come from.
  • Reproduce the core statement of Hewlett-Packard 9100A from memory before moving on to harder problems.

Reference excerpt

The Hewlett-Packard 9100A (HP 9100A) is an early programmable calculator (or computer), first appearing in 1968. HP called it a desktop calculator because, as Bill Hewlett said, "If we had called it a computer, it would have been rejected by our customers' computer gurus because it didn't look like an IBM. We therefore decided to call it a calculator, and all such nonsense disappeared." An ad for the 9100A in 1968 Science magazine contains one of the earliest documented use (as of 2000) of the phrase personal computer.

History

The device descended from a prototype designed by engineer Thomas "Tom" E. Osborne, who joined the company when HP adopted his idea. An engineering triumph, the logic circuit was produced without any integrated circuits. The CPU was entirely executed using discrete components. With CRT readout, magnetic card storage, and printer, the price was around US$4,900 (equivalent to $45,000 in 2025). Thanks to its high speed operation an order of magnitude faster than competitors – addition or subtraction took just 2 ms, multiplication 22 ms and division 27 ms – the device could quickly execute not just regular trigonometric functions (330 ms) or logarithms (130 ms) but many iterative computations when following a program. This made the 9100A the first scientific calculator by the modern definition, and also marked the beginning of Hewlett-Packard's long history of using Reverse Polish notation (RPN) entry on their calculators. Due to the similarities of their machines, Hewlett-Packard was ordered to pay about $900,000 in royalties to Olivetti after copying some of the features adopted from the Programma 101, like the magnetic card and the architecture.

See also HP-35 CORDIC

References

External links "HP 9100A Calculator (marketing brochure)" (PDF). Hewlett-Packard. 1968. Retrieved 2013-01-26. Hosted at the Computer History Museum. "HP 9100A/B". The Museum of HP Calculators. Retrieved 2013-01-26. Bell, C. Gordon; Newell, Allen (1971). "Chapter 20: The HP Model 9100A computing calculator". Computer Structures: Readings and Examples. McGraw-Hill. p. 243. ISBN 0-07-004357-4. Retrieved 2009-12-18. Steven Leibson interview of Tom Osborne

Illustrations

Hewlett-Packard 9100A: "The new Hewlett-Packard 9100A personal computer" is "ready, willing, and able... to relieve you of waiting to get on the big computer."[1][2]
"The new Hewlett-Packard 9100A personal computer" is "ready, willing, and able... to relieve you of waiting to get on the big computer."[1][2]
Hewlett-Packard 9100A: Electronic calculator prototype, made by Thomas E. Osborne for Hewlett-Packard, 1964, in the National Museum of American History
Electronic calculator prototype, made by Thomas E. Osborne for Hewlett-Packard, 1964, in the National Museum of American History

Worked examples

Example 1 — a first encounter with Hewlett-Packard 9100A

Start with the simplest possible case. Write down what Hewlett-Packard 9100A claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In computer science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Hewlett-Packard 9100A before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Hewlett-Packard 9100A ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Hewlett-Packard 9100A

In research
Hewlett-Packard 9100A appears in computer science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry
Engineering practice reuses Hewlett-Packard 9100A in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom
Hewlett-Packard 9100A is common in secondary-school and first-year university syllabi. It links to neighbouring topics Computer-related introductions in 1968, Computer hardware stubs, HP programmable calculators, so understanding it makes those chapters shorter.
In everyday life
Look for Hewlett-Packard 9100A outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.
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How to study Hewlett-Packard 9100A in 20 minutes

  1. Read the reference excerpt below once, without taking notes.
  2. Close the page and write down what Hewlett-Packard 9100A means in your own words.
  3. Compare your version with the excerpt and mark what you missed.
  4. Work through the three examples above with pen and paper.
  5. Explain Hewlett-Packard 9100A out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Hewlett-Packard 9100A in simple terms?

The Hewlett-Packard 9100A (HP 9100A) is an early programmable calculator (or computer), first appearing in 1968. HP called it a desktop calculator because, as Bill Hewlett said, "If we had called it a computer, it would have been rejected by our customers' computer gurus because it didn't look like…

Why does Hewlett-Packard 9100A matter?

Because it connects several computer science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Hewlett-Packard 9100A?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Hewlett-Packard 9100A.

Tags

  • Computer-related introductions in 1968
  • Computer hardware stubs
  • HP programmable calculators

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