積み上げ電卓　とんとん

Mistype once, start over from scratch. We got rid of that. You hit the key next to the one you meant. By the time you notice, the calculation has moved on, and an ordinary calculator has already thrown the steps away. You can’t see where it went wrong, so you start again. Tonton keeps the formula. Every number behind an answer stays visible, and you can fix it anywhere, any time. ■ One calculation, one named band Type 12,800 × 4 = 51,200 and the whole thing stays as a band. Name it “Train”. The longer the calculation, the harder it is to remember what each number in the middle was. With a name on every band, you can see at a glance which number is which, however many bands there are. No more stopping to wonder “what was this?” ■ Fix it anywhere, any time Tap any number in any formula and retype it. While you are still typing, after the band is done, or several bands back — it works the…