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TI-81
  • Introduction
  • Photo
  • Model Specifications
  • Official Information
  • ROM Versions
  • Unofficial Upgrades
  • Assembly Programming
  • Emulators
  • INTRODUCTION

    The TI-81, TI's first graphing calculator, was designed for algebra and precalculus. It has since been replaced by newer models which have faster processors, more memory, and popular features such as linking capability and flash upgradability. The TI-81 drew little in the way of third-party games and other programs, since the code must be typed into the calculator by hand.

    PHOTO

    TI-81

    MODEL SPECIFICATIONS

    TI-81
    CPU 2 MHz ZiLOG Z80
    Memory 2.4K RAM
    Screen Size 96x64 pixels, 16x8 characters
    Link Port? No
    CBL/CBR Support? No
    ViewScreen Model Available? Yes
    TI-Presenter Compatible? No
    TI Keyboard Compatible? No
    TI-Navigator Compatible? No

    OFFICIAL INFORMATION

    » Guide Books from Texas Instruments

    ROM VERSIONS

    From time to time, TI will update the internal code of their calculators to work around bugs, optimize functions, and even add features. This results in several versions of each calculator in the marketplace. You can check the ROM version of your TI-81 using the following key sequence and reading the number on your screen:

    [TEST] [ALPHA] [S]

    WARNING: After entering the above key sequence, DO NOT PRESS ENTER! If you do, your calculator's memory will be erased during the self-test sequence. Press any other key to exit back harmlessly.

    Known ROM versions:

    • 1.0 (Engineering sample)
    • 1.1
    • 1.8K
    • 2.0V

    UNOFFICIAL UPGRADES

    » Power Extension Page
    The Power Extension instructions will show you how to use AA (instead of AAA) batteries without making any modifications to your calculator.

    » TI-81 Turbo Page
    Internal modifications to your TI-81 can overclock the calculator to 3-4 times its original speed.

    ASSEMBLY PROGRAMMING

    History: Assembly language programming was not supported by TI when the TI-81 was released. As with the TI-82, TI-85, and TI-92, the calculator had to be "hacked" to enable assembly programming.

    With the TI-81's lack of a link port and thus no possibility of directly manipulating RAM, assembly programming on this model was for years simply considered impossible by definition, and the concept was completely ignored. A surprise came in 2009, nearly two decades after the TI-81's introduction, when a method was devised of executing arbitrary machine code using only the keyboard. The method exploits a bug in the ROM that allows the processor stack to overflow into the user RAM area, which can then be manipulated by modifying the contents of certain calculator variables.

    Unfortunately, given the need to execute a complex and lengthy series of keystrokes, type in programs by hand, the lack of RAM, and the increasing rarity of this long-discontinued model, TI-81 assembly programming is perhaps more of a novelty than a practicality.

    » TI-81 Software Environment Documentation
    » TI-81 ASM hook interrupt
    » Unity (TI-81 assembly loader)

    EMULATORS

    Several emulators are available to let you simulate TI calculators on your computer.

    Emulator Software
    Name Platform   Calculator(s)
     jsTIfied Javascript/HTML5 Home Page  73 81  82  83  83+  83+ SE  84+  84+ SE  84+ C SE                   
      Mac-81 MacOS     81                                 
      PC-81 DOS     81                                 
      TilEm 2.x Windows Home Page  73   81   82   83   83+   83+ SE  84+   84+ SE    85   86                
      TilEm 2.x Unix Home Page  73   81   82   83   83+   83+ SE  84+   84+ SE    85   86                

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