The C-x * k (calc-keypad) command starts the Calculator
and displays a picture of a calculator-style keypad. If you are using
the X window system, you can click on any of the “keys” in the
keypad using the left mouse button to operate the calculator.
The original window remains the selected window; in Keypad mode
you can type in your file while simultaneously performing
calculations with the mouse.
If you have used C-x * b first, C-x * k instead invokes
the full-calc-keypad command, which takes over the whole
Emacs screen and displays the keypad, the Calc stack, and the Calc
trail all at once. This mode would normally be used when running
Calc standalone (see Standalone Operation).
If you aren’t using the X window system, you must switch into the *Calc Keypad* window, place the cursor on the desired “key,” and type SPC or RET. If you think this is easier than using Calc normally, go right ahead.
Calc commands are more or less the same in Keypad mode. Certain keypad keys differ slightly from the corresponding normal Calc keystrokes; all such deviations are described below.
Keypad mode includes many more commands than will fit on the keypad
at once. Click the right mouse button [calc-keypad-menu]
to switch to the next menu. The bottom five rows of the keypad
stay the same; the top three rows change to a new set of commands.
To return to earlier menus, click the middle mouse button
[calc-keypad-menu-back] or simply advance through the menus
until you wrap around. Typing TAB inside the keypad window
is equivalent to clicking the right mouse button there.
You can always click the EXEC button and type any normal Calc key sequence. This is equivalent to switching into the Calc buffer, typing the keys, then switching back to your original buffer.