Simple calculator

Enter the numbers in the two boxes then tap an operator.

The result will appear in the top box and the bottom box will be empty, ready to enter another number to continue a chain calculation.

Because this is really a simplified RPN calculator, two useful RPN utilities are also available:

1. "Swap" exchanges the contents of the top and bottom boxes.

2. "Dup" copies the content of the top box into the bottom box.