TabulatorI found an old adding machine at a local thrift store, and thought it would be a really cool thing to have.  For a couple of bucks, I didn't expect it to work, and when I first tried it it was almost completely non-functional.  So little of it worked that I couldn't even figure out how it was supposed to work.  In particular, I'd seen references to clearing the machine before beginning a calculation, but none of the keys seemed to do anything close to resetting it to all zeros.