Texas Instruments TI-83 Plus Graphing Calculator with Slide Cover Tested Working This calculator was a life-saver and played a HUGE role in me getting my Engineering degree. It's a little sad to let it go, but honestly, as a working engineer I never do any complicated math! All that calculus for nothing!! Haha. I put fresh batteries in it (it takes 4 AAA batteries) and it has a backup battery as well. That one I did not change out. The buttons are a little discolored from age and use - I think that adds to the nostalgia (and luck).