Fraction Formats
----------------

Display of fractional numbers is controlled by the `d o'
(`calc-over-notation') command.  By default, a number like eight
thirds is displayed in the form `8:3'.  The `d o' command prompts for
a one- or two-character format.  If you give one character, that
character is used as the fraction separator.  Common separators are
`:' and `/'.  (During input of numbers, the `:' key must be used
regardless of the display format; in particular, the `/' is used for
RPN-style division, *not* for entering fractions.)

If you give two characters, fractions use
"integer-plus-fractional-part" notation.  For example, the format `+/'
would display eight thirds as `2+2/3'.  If two colons are present in a
number being entered, the number is interpreted in this form (so that
the entries `2:2:3' and `8:3' are equivalent).

It is also possible to follow the one- or two-character format with a
number.  For example: `:10' or `+/3'.  In this case, Calc adjusts all
fractions that are displayed to have the specified denominator, if
possible.  Otherwise it adjusts the denominator to be a multiple of
the specified value.  For example, in `:6' mode the fraction `1:6'
will be unaffected, but `2:3' will be displayed as `4:6', `1:2' will
be displayed as `3:6', and `1:8' will be displayed as `3:24'.
Integers are also affected by this mode: 3 is displayed as `18:6'.
Note that the format `:1' writes fractions the same as `:', but it
writes integers as `n:1'.

The fraction format does not affect the way fractions or integers are
stored, only the way they appear on the screen.  The fraction format
never affects floats.