computer science

TI-81

TI-81 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 TI-81 rather than just read about it. In short: The TI-81 was the first graphing calculator made by Texas Instruments. It was designed in 1990 for use in algebra and pre-calculus courses.

Key takeaways

TI-81 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 TI-81 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of TI-81 from memory before moving on to harder problems.

Reference excerpt

The TI-81 was the first graphing calculator made by Texas Instruments. It was designed in 1990 for use in algebra and pre-calculus courses. Since its release, it has been superseded by a series of newer calculators; most of these are functionally similar to the TI-81, with the exception of the TI-Nspire series.

Features The TI-81 is powered by a Zilog Z80 microprocessor, as used in the TI-73 and TI-81 to TI-86 graphing calculators. However, its processor is clocked at 2 MHz, whereas the others run at a frequency of either 6 or 15 MHz. It has 2.4 KB of user-accessible RAM, with additional RAM being allocated to the calculator's internal firmware. The calculator uses Texas Instruments' own in-house operating system, the Equation Operating System; the firmware used by all other Texas Instruments graphing calculators derive from this. The TI-81 can perform two-dimensional parametric graphing—in addition to standard two-dimensional function graphing, trigonometric calculations in units of either degrees or radians, simple drawing, the creation and manipulation of matrices up to a size of 6 by 6, and the execution of simple programs in a proprietary, statement-based language. In late 2009 an exploit was found that can be used to execute machine code on the TI-81, using manual input of code. The TI-81 has no data link interface; its only means of input and output are the keyboard and screen. Like most other Texas Instruments graphing calculators, the TI-81 is powered by four AAA batteries and one button cell backup battery; the backup battery ensures that programs loaded in memory are retained during battery changes. Some early TI-81 units omit the backup battery. Texas Instruments produced an emulator for the TI-81 and its Equation Operating System on a desktop computer; it is compatible with MS-DOS.

See also Comparison of Texas Instruments graphing calculators

References

External links ticalc.org – The largest archive of TI programs available.

Illustrations

Worked examples

Example 1 — a first encounter with TI-81

Start with the simplest possible case. Write down what TI-81 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 TI-81 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 TI-81 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 TI-81

In research: TI-81 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 TI-81 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: TI-81 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Computer-related introductions in 1990, Graphing calculators, Texas Instruments programmable calculators, so understanding it makes those chapters shorter.
In everyday life: Look for TI-81 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 TI-81 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what TI-81 means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain TI-81 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is TI-81 in simple terms?

The TI-81 was the first graphing calculator made by Texas Instruments. It was designed in 1990 for use in algebra and pre-calculus courses.

Why does TI-81 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 TI-81?

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 TI-81.