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The `'` (`calc-algebraic-entry`

) command can be used to enter
calculations in algebraic form. This is accomplished by typing the
apostrophe key, ’, followed by the expression in standard format:

```
' 2+3*4 RET.
```

This will compute
‘`2+(3*4) = 14`’
and push it on the stack. If you wish you can
ignore the RPN aspect of Calc altogether and simply enter algebraic
expressions in this way. You may want to use `DEL` every so often to
clear previous results off the stack.

You can press the apostrophe key during normal numeric entry to switch the half-entered number into Algebraic entry mode. One reason to do this would be to fix a typo, as the full Emacs cursor motion and editing keys are available during algebraic entry but not during numeric entry.

In the same vein, during either numeric or algebraic entry you can
press ``` (backquote) to switch to `calc-edit`

mode, where
you complete your half-finished entry in a separate buffer.
See Editing Stack Entries.

If you prefer algebraic entry, you can use the command `m a`
(`calc-algebraic-mode`

) to set Algebraic mode. In this mode,
digits and other keys that would normally start numeric entry instead
start full algebraic entry; as long as your formula begins with a digit
you can omit the apostrophe. Open parentheses and square brackets also
begin algebraic entry. You can still do RPN calculations in this mode,
but you will have to press `RET` to terminate every number:
`2 RET 3 RET * 4 RET +` would accomplish the same
thing as `2*3+4 RET`.

If you give a numeric prefix argument like `C-u` to the `m a`
command, it enables Incomplete Algebraic mode; this is like regular
Algebraic mode except that it applies to the `(` and `[` keys
only. Numeric keys still begin a numeric entry in this mode.

The `m t` (`calc-total-algebraic-mode`

) gives you an even
stronger algebraic-entry mode, in which *all* regular letter and
punctuation keys begin algebraic entry. Use this if you prefer typing
`sqrt( )` instead of `Q`, `factor( )` instead of
`a f`, and so on. To type regular Calc commands when you are in
Total Algebraic mode, hold down the `META` key. Thus `M-q`
is the command to quit Calc, `M-p` sets the precision, and
`M-m t` (or `M-m M-t`, if you prefer) turns Total Algebraic
mode back off again. Meta keys also terminate algebraic entry, so
that `2+3 M-S` is equivalent to `2+3 RET M-S`. The symbol
‘`Alg*`’ will appear in the mode line whenever you are in this mode.

Pressing `'` (the apostrophe) a second time re-enters the previous
algebraic formula. You can then use the normal Emacs editing keys to
modify this formula to your liking before pressing `RET`.

Within a formula entered from the keyboard, the symbol `$`
represents the number on the top of the stack. If an entered formula
contains any `$` characters, the Calculator replaces the top of
stack with that formula rather than simply pushing the formula onto the
stack. Thus, `' 1+2 RET` pushes 3 on the stack, and `$*2
RET` replaces it with 6. Note that the `$` key always
initiates algebraic entry; the `'` is unnecessary if `$` is the
first character in the new formula.

Higher stack elements can be accessed from an entered formula with the
symbols `$$`, `$$$`, and so on. The number of stack elements
removed (to be replaced by the entered values) equals the number of dollar
signs in the longest such symbol in the formula. For example, ‘`$$+$$$`’
adds the second and third stack elements, replacing the top three elements
with the answer. (All information about the top stack element is thus lost
since no single ‘`$`’ appears in this formula.)

A slightly different way to refer to stack elements is with a dollar
sign followed by a number: ‘`$1`’, ‘`$2`’, and so on are much
like ‘`$`’, ‘`$$`’, etc., except that stack entries referred
to numerically are not replaced by the algebraic entry. That is, while
‘`$+1`’ replaces 5 on the stack with 6, ‘`$1+1`’ leaves the 5
on the stack and pushes an additional 6.

If a sequence of formulas are entered separated by commas, each formula
is pushed onto the stack in turn. For example, ‘`1,2,3`’ pushes
those three numbers onto the stack (leaving the 3 at the top), and
‘`$+1,$-1`’ replaces a 5 on the stack with 4 followed by 6. Also,
‘`$,$$`’ exchanges the top two elements of the stack, just like the
`TAB` key.

You can finish an algebraic entry with `M-=` or `M-RET` instead
of `RET`. This uses `=` to evaluate the variables in each
formula that goes onto the stack. (Thus `' pi RET` pushes
the variable ‘`pi`’, but `' pi M-RET` pushes 3.1415.)

If you finish your algebraic entry by pressing `LFD` (or `C-j`)
instead of `RET`, Calc disables simplification
(as if by `m O`; see Simplification Modes) while the entry
is being pushed on the stack. Thus `' 1+2 RET` pushes 3
on the stack, but `' 1+2 LFD` pushes the formula ‘`1+2`’;
you might then press `=` when it is time to evaluate this formula.

Next: Quick Calculator, Previous: Numeric Entry, Up: Introduction [Contents][Index]