A different calculator

We have added a different calculator to the app. Why? Let us start with a bit of history.

To begin with, not every people had counting. Some got by with just three notions - one, two, many. For a while that was enough.

As civilisation developed, people learned to count on their fingers. We still count on our fingers sometimes. If you have ever done it, you have probably noticed that once you reach 10 you have to improvise, because we have 10 fingers (normally).

The breakthrough was the invention of the abacus about 5000 years ago. It took many forms, but the one we picture is a rectangle with thin horizontal rods, each holding 10 beads (the number of fingers on a pair of hands).

That solved the problem of tens. Say we need to add 5 and 6. We slide 5 beads on the bottom rod to the right. That is 5.

Now we need to add 6. But only 5 beads are left on the first row. We slide them to the right. Now 10 beads are on the right. That is 10. We slide them all back to the left and slide one bead to the right on the second rod from the bottom.

We needed to add 6, we have already added five, one is left. We slide one bead to the right on the bottom rod.

The result - the two bottom rods, each with one bead slid to the right. That is 11. As recently as 50 years ago, shop assistants counted on an abacus no slower than today's digital tills with barcode scanners.

A few thousand years later mechanical calculators began to appear, capable of far more complex arithmetic. Then came electronic calculators, and then calculators inside computers.

But!

They all share the same drawback - you cannot simply correct a mistake you have already made. Say you need to work out this expression:

12 * 555 * 4 - 345 + 45

You typed 777 instead of 555 and only noticed it as you were subtracting 345. That is it, you have to start over.

But why?

Why not let the user write it in a text field instead:

12 * 555 * 4 - 345 + 45

The result can be recalculated while you type. Then the user notices the mistake, changes 777 back to 555, and the result updates. Nothing has to be started over.

The result is a different calculator. You can try it right here.