Calculator

Every number is held as digits and a power of ten rather than as a float, so 0.1 plus 0.2 is 0.3 and stays 0.3 through the rest of the sum. Division and the trigonometry are worked to thirty four significant digits and shown to seventeen.

Percent reads the way it does on every other calculator: 200 plus 10 percent is 220, and 200 times 10 percent is 20. Programmer holds its numbers in two's complement at the word length you pick, and every bit in the grid is a switch.