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http://edspi31415.blogspot.com/2019/09/r...ti-66.html

Company: Texas Instruments
Years in Production: 1982 to 1985
Original Price: I estimate the original price to be from $70 to $100
Battery: 2 x LR44 or 2 x AR76
Type: Scientific, Keystroke Programmable
Operating System: AOS
Number of Digits: 10
Memory: 512 steps, which can be allocated to a maximum of 64 memory registers
Accessories: Carrying Case, PC-200 Printer

The TI-66 was slated to be the next generation of the TI-58C of 1978. Virtually the keyboard design and commands of the TI-58C are present in the TI-66, but there are some differences:
* The TI-66 is an landscape form with a gray keyboard, where as the TI-58C (and the related TI-58 and TI-59 has a black keyboard).
* The TI-66 lacks a card reader.
* The TI-66 also lacked a slot for modules.
* However, the TI-66 runs on coin batteries (AR76 or LR44), which can be found easily. The TI-58C family had rechargeable battery packs, which cannot be easily purchased (few vendors sell them online).
* In learn mode, when a step is registered, the TI-66 displays the key you just pressed with its mnemonic.

Thanks for the review, Eddie.

As a collector point of view, this is one of my preferred Texas machines.
It may be slow, but it saves energy and the battery last for many years.

My take centered on the hardware side of things:
https://www.hpmuseum.org/forum/thread-28...l#pid24536

This reminded me of the TI-65 "Technical Analyst" (amazing name for a calculator, I think). One of TI's programmables which came with lots of features geared toward STEM work. I found the selection of physical constants interesting.

Curiously, it lacked hyperbolic functions so I tried programming in some using the exponential function. Took the machine couple seconds to chug them out, haha.

Jebem,

I enjoy your tear down posts of calculators.

Benjer,

I don't know why TI only had 100 steps for the TI-65, it could have been the successor in the TI-58 family. I love the 65's carrying case.

Eddie