I created my own calculator. And no electricity needed, it runs on its own power! No batteries or electric cord needed.
It does the calculating job instantly, even quicker than the Chinese Abacus, but more primitive.
On my walk a made a certain route, which ends where I started. Each day, I have a goal of the number of times to walk this route. And more times than not I get the number of loops I have already mixed up.
My solution: Put 5 small rocks at the starting point and each time you make a lap move one rock over to a new pile. When all the little rocks are on one side you know you have walked 5 laps. Then the next lap you would move a rock from that pile and start a new pile.
I’m sure Apple and Texas Instrument are having fits over this.