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TI - Graphing Calculators

If you went to school in the US during the 1990s, and in to the early 2000s, you probably owned, or at least used, a Texas Instruments 80s Series calculator.

The TI-81 was released in 1990 and immediately gained ground in schools across America. This z80 based hand-held computer was able to do anything a scientific calculator could do. It even included TI Basic, a Basic language which allowed users to write in programs to solve very complex problems. None of this was really new. Programmable calculators had been out for years. But the new trick up this calculator's sleeve, was the ability to draw graphics; specifically graphs.
This was obviously something that was typically reserved for more capable computers at the time.
For less than $150, you could own a hand held computer.
School districts across the country began purchasing class sets. TI made it easy by bundling sets with a teacher's edition of the calculator. The teacher's edition was specially modified so it could connect to an external lcd screen and be projected on the wall. (More on those another day.)

But the TI-81 had one fatal flaw. Something that really kept it from becoming the defacto standard.
Every single person had to manually enter in thier own programs. This meant that if you came up with something amazing, you couldn't share it. Worse, changing the batteries wiped the full memory.

This limitation didn't last long as Texas Imstruments released the TI-85 in 1992.
This new model used the same z80 processor, bit was somehow now many times faster.
This new calculator corrected many issues with the TI-81 including adding a backup/coin-cell battery (they added this to the TI-81 around the same time. But it wasn't there originally.) And the greatest improvement of all...
TI-Link
This new, little cable, meant that programs could be shared between students and teachers. The cable, which was simply a 3-wire cord with a 2.5mm jack on each end, changed the world for students.
Very soon after the release of the calculator, Texas Instruments released the TI-Graph Link cable, a serial cable allowing users to connect the TI-85 to a windows 3.11 or Mac OS computer, copy files and even write programs on the computer.

This new calculator came at a much higher price, preventing it from gaining mass adoption.

To be continued....