Graphical Calculator Plus

Graphical calculator featuring:
- Basic Operations
- Digit buttons for the user input of numbers.
- Additional operation buttons like sin, cos, log, √, x²
- Provide +/- button to change the leading sign. If user is entering a number, switch the sign of the main display. Else handle it like an operator, to math the last operation's result by * (-1).
- π button to enter Pi and push it onto the calculator stack.
- 1/x button delivers functionality to calculate reversal numbers.
- variable display in the view to display the variable with values, which are used in the current program.
- Reverse Polish notation.