Hot Footer is a virtual tape calculator; that is, it mimics an analog device that printed a log of one's calculations onto a paper tape.
I've never understood why they went out of fashion. I find that once the column of figures I'm adding an addition column has more than ten entries, I have to add the thing twice and compare the two tapes with the paper I'm working from. When I was reviewing audit workpapers, I looked for the tapes when we proved to prove a long calculation.
The logic of a tape calculator is different from that of the usual algebraic calculator. Typing the plus or minus key after the number places the amount on the tape and updates the internal total register. So to add 4 plus 5 enter:
| Entry | Tape shows |
|---|---|
| 2+ | 2 + |
| 5+ | 5 + |
| = |
----------- 7 T =========== |
Typing the equals key prints the total and clears the total register. Multiplication and division work similarly to an algebraic calculator in that one types the number, the operation to perform, and the equals key after that last number. If one follows the last number with a plus (or minus) key, the calculator prints the result and adds (or subtracts) the result from the total register.
The advantage in this logic becomes clear when you have a long list of both positive and negative numbers. I use a ruler to mark my place, and with having the operator (sign) on the same line, it’s makes it relatively easy to keep my place and to reconcile the column of numbers.
I obsessively chase down every cent we spend, and I couldn’t do it without Hot Footer.