The TI-80 was released with Algebra I and middle school students in mind. Like
the TI-81, it has no link port and is not intended for serious programming.
The TI-80's newer cousin, the TI-73, sports flash upgradability and more
memory, and has completely replaced the TI-80 in everyday use.
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» Guide Books from Texas Instruments
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-80 using the following key sequence and reading the number
on your screen:
[MODE] [ALPHA] [S]
WARNING: After entering the above key sequence, DO NOT PRESS ENTER! If you
do, your calculator's memory will be erased. Press any other key to exit back
Known ROM versions:
» 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.
» Tutorials at TI-Freakware