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### 16.1 Main Menu

         |----+----+--Calc---+----+----1
         |FLR |CEIL|RND |TRNC|CLN2|FLT |
         |----+----+----+----+----+----|
         | LN |EXP |    |ABS |IDIV|MOD |
         |----+----+----+----+----+----|
         |SIN |COS |TAN |SQRT|y^x |1/x |
         |----+----+----+----+----+----|
         |  ENTER  |+/- |EEX |UNDO| <- |
         |-----+---+-+--+--+-+---++----|
         | INV |  7  |  8  |  9  |  /  |
         |-----+-----+-----+-----+-----|
         | HYP |  4  |  5  |  6  |  *  |
         |-----+-----+-----+-----+-----|
         |EXEC |  1  |  2  |  3  |  -  |
         |-----+-----+-----+-----+-----|
         | OFF |  0  |  .  | PI  |  +  |
         |-----+-----+-----+-----+-----+

This is the menu that appears the first time you start Keypad mode. It will show up in a vertical window on the right side of your screen. Above this menu is the traditional Calc stack display. On a 24-line screen you will be able to see the top three stack entries.

The ten digit keys, decimal point, and <EEX> key are used for entering numbers in the obvious way. <EEX> begins entry of an exponent in scientific notation. Just as with regular Calc, the number is pushed onto the stack as soon as you press <ENTER> or any other function key.

The <+/-> key corresponds to normal Calc's `n` key. During numeric entry it changes the sign of the number or of the exponent. At other times it changes the sign of the number on the top of the stack.

The <INV> and <HYP> keys modify other keys. As well as having the effects described elsewhere in this manual, Keypad mode defines several other “inverse” operations. These are described below and in the following sections.

The <ENTER> key finishes the current numeric entry, or otherwise duplicates the top entry on the stack.

The <UNDO> key undoes the most recent Calc operation. `INV UNDO` is the “redo” command, and `HYP UNDO` is “last arguments” (`M-<RET>`).

The <<-> key acts as a “backspace” during numeric entry. At other times it removes the top stack entry. `INV <-` clears the entire stack. `HYP <-` takes an integer from the stack, then removes that many additional stack elements.

The <EXEC> key prompts you to enter any keystroke sequence that would normally work in Calc mode. This can include a numeric prefix if you wish. It is also possible simply to switch into the Calc window and type commands in it; there is nothing “magic” about this window when Keypad mode is active.

The other keys in this display perform their obvious calculator functions. <CLN2> rounds the top-of-stack by temporarily reducing the precision by 2 digits. <FLT> converts an integer or fraction on the top of the stack to floating-point.

The <INV> and <HYP> keys combined with several of these keys give you access to some common functions even if the appropriate menu is not displayed. Obviously you don't need to learn these keys unless you find yourself wasting time switching among the menus.

`INV +/-`
  is the same as <1/x>.
`INV +`
  is the same as <SQRT>.
`INV -`
  is the same as <CONJ>.
`INV *`
  is the same as <y^x>.
`INV /`
  is the same as <INV y^x> (the ‘`x`’th root of ‘`y`’).
`HYP/INV 1`
  are the same as <SIN> / `INV SIN`.
`HYP/INV 2`
  are the same as <COS> / `INV COS`.
`HYP/INV 3`
  are the same as <TAN> / `INV TAN`.
`INV/HYP 4`
  are the same as <LN> / `HYP LN`.
`INV/HYP 5`
  are the same as <EXP> / `HYP EXP`.
`INV 6`
  is the same as <ABS>.
`INV 7`
  is the same as <RND> (`calc-round`).
`INV 8`
  is the same as <CLN2>.
`INV 9`
  is the same as <FLT> (`calc-float`).
`INV 0`
  is the same as <IMAG>.
`INV .`
  is the same as <PREC>.
`INV ENTER`
  is the same as <SWAP>.
`HYP ENTER`
  is the same as <RLL3>.
`INV HYP ENTER`
  is the same as <OVER>.
`HYP +/-`
  packs the top two stack entries as an error form.
`HYP EEX`
  packs the top two stack entries as a modulo form.
`INV EEX`
  creates an interval form; this removes an integer which is one of 0 ‘`[]`’, 1 ‘`[)`’, 2 ‘`(]`’ or 3 ‘`()`’, followed by the two limits of the interval.

The `OFF` key turns Calc off; typing `C-x * k` or `C-x * *` again has the same effect. This is analogous to typing `q` or hitting `C-x * c` again in the normal calculator. If Calc is running standalone (the `full-calc-keypad` command appeared in the command line that started Emacs), then `OFF` is replaced with `EXIT`; clicking on this actually exits Emacs itself.