All buttons can be activated with either the mouse or keyboard. The keypad works as expected, with the enter key, as well as the return key, equivalent to the [ = ] button on the calculator. If you don't have a keypad, you can enable the Keypad Emulation option, and use the M, J, K, L, U, I, O, 7, 8, and 9 keys as a numeric keypad.
Some of the buttons also have a secondary function that can be activated either by first pressing the [2nd] button or by holding down the control key while pressing the button. Pressing the [2nd] button or control key immediately changes the relevant buttons to indicate their new functions.
To switch between the full-function and the reduced four-function calculators, press the zoom box in the window's title bar. The four-function mode is similar in design and function to the Apple Calculator.
