are copied from the currently active buffer when a buffer is
first entered.  If 'S' is present the options are copied each time the buffer
is entered, this is almost like having global options.  If 's' and 'S' are not
present, the options are copied from the currently active buffer when the
buffer is created.

Hidden options						*hidden-options*

Not all options are supported in all versions.  This depends on the supported
features and sometimes on the system.  A remark about this is in curly braces
below.  When an option is not supported, it is called a hidden option.  Trying
to get the value of a hidden option will not give an error, it will return the
default value for that option instead. You can't change the value of a hidden
option.

To test if "foo" is a valid option name, use something like this: >
	if exists('&foo')
This also returns true for a hidden option.  To test if option "foo" is really
supported use something like this: >
	if exists('+foo')
<
							*E355*
A jump table for the options with a short description can be found at |Q_op|.

			*'allowrevins'* *'ari'* *'noallowrevins'* *'noari'*
'allowrevins' 'ari'	boolean	(default off)
			global
	Allow CTRL-_ in Insert mode.  This is default off, to avoid that users
	that accidentally type CTRL-_ instead of SHIFT-_ get into reverse
	Insert mode, and don't know how to get out.  See 'revins'.

						*'ambiwidth'* *'ambw'*
'ambiwidth' 'ambw'	string	(default "single")
			global
	Tells Vim what to do with characters with East Asian Width Class
	Ambiguous (such as Euro, Registered Sign, Copyright Sign, Greek
	letters, Cyrillic letters).

	There are currently two possible values:
	"single":	Use the same width as characters in US-ASCII.  This is
			expected by most users.
	"double":	Use twice the width of ASCII characters.
							*E834* *E835*
	The value "double" cannot be used if 'listchars' or 'fillchars'
	contains a character that would be double width.  These errors may
	also be given when calling setcellwidths().

	The values are overruled for characters specified with
	|setcellwidths()|.

	There are a number of CJK fonts for which the width of glyphs for
	those characters are solely based on how many octets they take in
	legacy/traditional CJK encodings.  In those encodings, Euro,
	Registered sign, Greek/Cyrillic letters are represented by two octets,
	therefore those fonts have "wide" glyphs for them.  This is also
	true of some line drawing characters used to make tables in text
	file.  Therefore, when a CJK font is used for GUI Vim or
	Vim is running inside a terminal (emulators) that uses a CJK font
	(or Vim is run inside an xterm invoked with "-cjkwidth" option.),
	this option should be set to "double" to match the width perceived
	by Vim with the width of glyphs in the font.  Perhaps it also has
	to be set to "double" under CJK MS-Windows when the system locale is
	set to one of CJK locales.  See Unicode Standard Annex #11
	(https://www.unicode.org/reports/tr11).

				*'arabic'* *'arab'* *'noarabic'* *'noarab'*
'arabic' 'arab'		boolean	(default off)
			local to window
	This option can be set to start editing Arabic text.
	Setting this option will:
	- Set the 'rightleft' option, unless 'termbidi' is set.
	- Set the 'arabicshape' option, unless 'termbidi' is set.
	- Set the 'keymap' option to "arabic"; in Insert mode CTRL-^ toggles
	  between typing English and Arabic key mapping.
	- Set the 'delcombine' option

	Resetting this option will:
	- Reset the 'rightleft' option.
	- Disable the use of 'keymap' (without changing its value).
	Note that 'arabicshape' and 'delcombine' are not reset (it is a global
	option).
	Also see |arabic.txt|.

		*'arabicshape'* *'arshape'* *'noarabicshape'* *'noarshape'*
'arabicshape' 'arshape'	boolean	(default on)
			global
	When on and 'termbidi' is off, the required visual character
	corrections that need to take place for displaying the Arabic language
	take effect.  Shaping, in essence, gets enabled; the term is a broad
	one which