HMS Formats
-----------

The `d h' (`calc-hms-notation') command controls the display of HMS
(hours-minutes-seconds) forms.  It prompts for a string which consists
basically of an "hours" marker, optional punctuation, a "minutes"
marker, more optional punctuation, and a "seconds" marker.
Punctuation is zero or more spaces, commas, or semicolons.  The hours
marker is one or more non-punctuation characters.  The minutes and
seconds markers must be single non-punctuation characters.

The default HMS format is `@ ' "', producing HMS values of the form
`23@ 30' 15.75"'.  The format `deg, ms' would display this same value
as `23deg, 30m15.75s'.  During numeric entry, the `h' or `o' keys are
recognized as synonyms for `@' regardless of display format.  The `m'
and `s' keys are recognized as synonyms for `'' and `"', respectively,
but only if an `@' (or `h' or `o') has already been typed; otherwise,
they have their usual meanings (`m-' prefix and `s-' prefix).  Thus,
`5 "', `0 @ 5 "', and `0 h 5 s' are some of the ways to enter the
quantity "five seconds."  The `'' key is recognized as "minutes" only
if `@' (or `h' or `o') has already been pressed; otherwise it means to
switch to algebraic entry.