How it is calculated
The expression is parsed without eval. Numbers, brackets, and signs become reverse Polish notation. Percent is a postfix “divide by 100”, so 50% equals 0,5 rather than a percent of the previous number. The comma key is entered as a decimal point.
Order: brackets, percent, powers, multiplication and division, then addition and subtraction
Example
10 − 2 × 3 = 4, because multiplication comes first. (10 − 2) × 3 = 24. 2^3^2 = 512: a power is read from right to left.
Questions
Why doesn't 200 + 10% equal 220?
Here % divides the current number by 100. 10% is 0,1, so the sum is 200,1. A shop markup belongs in the percent calculator.
Can you divide by zero?
No, an error appears. The expression is not cleared quietly.
Is there memory, and percent of an intermediate result?
There is no memory. Use parentheses for a long formula.