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A 1994 TI-81 showing graphs
TypeGraphing calculator
ManufacturerTexas Instruments
Entry modeD.A.L.
Precision13 digits
Display size96×64 pixels, 16×8 characters
ProcessorZilog Z80
Frequency5 MHz or 6 MHz[2]
Programming language(s)TI-BASIC, Assembly
User memory2400 bytes of RAM
Power supply4 AAAs,
1 CR1616 or CR1620

The TI-81 was the first graphing calculator made by Texas Instruments. It was designed in 1990 for use in algebra and precalculus courses. Since its release, it has been superseded by a series of newer calculators: the TI-85, TI-82, TI-83, TI-86, TI-83 Plus, TI-83 Plus Silver Edition, TI-84 Plus, TI-84 Plus Silver Edition, TI-84 Plus C Silver Edition, TI-Nspire, TI-Nspire CAS, TI-84 Plus CE, and most recently, the TI-84 Plus CE Python. Most of them share the original feature set and 96×64-pixel display that began with this calculator, with the exceptions of the TI-84 Plus C Silver Edition and the TI-84 Plus CE family.


The TI-81 is powered by a Zilog Z80 microprocessor, like those used in almost every other Texas Instruments graphing calculator (except the TI-80, TI-89, TI-89 Titanium, TI-92, TI-92 Plus, Voyage 200 and TI-Nspire series). However, the processor is clocked at 2 MHz whereas the other Z80-powered Texas Instruments calculators run at speeds of at least 6 MHz (the TI-83 Plus Silver Edition, TI-84 Plus, and TI-84 Plus Silver Edition can run at 15 MHz). It contains 2400 bytes of user RAM, with additional RAM used internally by the calculator firmware software system.

The TI-81's user interactions are provided by its so-called Equation Operation System. This is comparable to the interface provided by the more recent TI-82, TI-83, and so on. This system is capable of such tasks as two-dimensional parametric graphing (in addition to standard two-dimensional function graphing), trigonometric calculations in units of either degrees or radians, simple drawing capabilities, creation and manipulation of matrices up to 6x6 in size, and programming in a proprietary statement-based language.[3]

In late 2009 an exploit was found that can be used to execute machine code on the TI-81, using manual input of code.[4] The TI-81 has no data link interface; its only means of input and output are the keyboard and screen.

As with its successors, the TI-81 is powered by four AAA batteries and one CR1616 or CR1620 lithium backup battery (to ensure programs are persistent when the AAA batteries are being changed). Some early TI-81 units omit the backup battery;[5] if the AAA batteries of one of these units are changed one at a time and quickly, the memory contents are still retained.

Texas Instruments distributes software which emulates the TI-81 and its Equation Operating System on a desktop computer using DOS[6] or DOSBox.

See also[edit]


  1. ^ Woerner, Joerg (2009-02-08). "DATAMATH: TI-81 (1995)". Retrieved 2013-01-27.
  2. ^ "TI-Planet's calculator comparison tool". TI-Planet.
  3. ^ Christiansen, Brad; et al. "TI-81 Guidebook" (PDF). Texas Instruments, Inc. pp. 8–9. Retrieved 2021-02-04.
  4. ^ Evans, Travis (2009-08-17). "User Machine Code Execution on TI-81 Becomes a Reality". Retrieved 2013-01-27.
  5. ^ Woerner, Joerg (2009-01-27). "DATAMATH: TI-81 Engineering Sample". Retrieved 2012-02-04.
  6. ^ "PC-81 on ticalc.org". 1998-04-28. Retrieved 2012-02-04.

External links[edit]

  • ticalc.org – The largest archive of TI programs available.