I recently bought a used TI-55-II on eBay. This is an old (early 80’s) Texas Instruments calculator, one the first programmable ones. I got it mostly for sentimental value, since I used to own one back in Brazil in 1983, my last year in high school.

Looking back, the fact that I got this specific programmable calculator exactly at that moment in my life was probably an important contributing factor to my choice of Computer Science when I joined the Federal University of Ceara in Brazil in 1984. Before that, I had my eyes set on Architecture. And not Computer or Systems Architecture, I should say, since back then we did not associate Architecture with Computer Science careers.

The TI-55-II is actually a pretty limited device by today’s standards. You have a 10-digit LCD display, 8 “memories” and 56 “programming steps”. Programming the calculator basically meant storing a sequence of keystrokes and you had no conditional statements, just one RST command to go back to step 0. Even with that, I remember being quite impressed with the ability to create a program, use multiple variables and display data on the screen (there is a PAUSE instruction to let you see a number on the screen before moving to the next step).

The calculator I used back in high school was actually manufactured in the city of Manaus in Brazil ("Produzida na Zona Franca de Manaus") by a subsidiary of Texas Instruments. I found some information about it on the internet: http://www.datamath.org/Sci/Slanted/TI-55-II-AA.htm. In fact, there is even a soft copy of the manual in PDF format: http://www.datamath.net/Manuals/TI-55-II_QR_US.pdf.

My used TI-55-II I got from eBay (shown on the right) was made in the US in 1982. It's almost the same as the Brazilian model except for the type of battery it uses. Details at http://www.datamath.org/Sci/Slanted/TI-55-II.htm. Mine is actually working fine and I even managed to remember how to create simple programs with it. Interesting how your brain can retain that kind of information decades later…

See also a previous blog post on CP/M and the TRS-80, which I used a few years after that: http://blogs.technet.com/josebda/archive/2009/08/07/the-good-old-days-of-cp-m-2-2-on-a-trs-80-with-an-8-bit-z80-cpu.aspx

 TI-55-II