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[Emacs-diffs] Changes to nonascii.texi
|
From: |
Glenn Morris |
|
Subject: |
[Emacs-diffs] Changes to nonascii.texi |
|
Date: |
Thu, 06 Sep 2007 04:22:17 +0000 |
CVSROOT: /sources/emacs
Module name: emacs
Changes by: Glenn Morris <gm> 07/09/06 04:22:17
Index: nonascii.texi
===================================================================
RCS file: nonascii.texi
diff -N nonascii.texi
--- /dev/null 1 Jan 1970 00:00:00 -0000
+++ nonascii.texi 6 Sep 2007 04:22:17 -0000 1.1
@@ -0,0 +1,1504 @@
address@hidden -*-texinfo-*-
address@hidden This is part of the GNU Emacs Lisp Reference Manual.
address@hidden Copyright (C) 1998, 1999, 2001, 2002, 2003, 2004,
address@hidden 2005, 2006, 2007 Free Software Foundation, Inc.
address@hidden See the file elisp.texi for copying conditions.
address@hidden ../info/characters
address@hidden Non-ASCII Characters, Searching and Matching, Text, Top
address@hidden address@hidden Characters
address@hidden multibyte characters
address@hidden characters, multi-byte
address@hidden address@hidden characters
+
+ This chapter covers the special issues relating to address@hidden
+characters and how they are stored in strings and buffers.
+
address@hidden
+* Text Representations:: Unibyte and multibyte representations
+* Converting Representations:: Converting unibyte to multibyte and vice versa.
+* Selecting a Representation:: Treating a byte sequence as unibyte or multi.
+* Character Codes:: How unibyte and multibyte relate to
+ codes of individual characters.
+* Character Sets:: The space of possible character codes
+ is divided into various character sets.
+* Chars and Bytes:: More information about multibyte encodings.
+* Splitting Characters:: Converting a character to its byte sequence.
+* Scanning Charsets:: Which character sets are used in a buffer?
+* Translation of Characters:: Translation tables are used for conversion.
+* Coding Systems:: Coding systems are conversions for saving files.
+* Input Methods:: Input methods allow users to enter various
+ non-ASCII characters without special keyboards.
+* Locales:: Interacting with the POSIX locale.
address@hidden menu
+
address@hidden Text Representations
address@hidden Text Representations
address@hidden text representations
+
+ Emacs has two @dfn{text representations}---two ways to represent text
+in a string or buffer. These are called @dfn{unibyte} and
address@hidden Each string, and each buffer, uses one of these two
+representations. For most purposes, you can ignore the issue of
+representations, because Emacs converts text between them as
+appropriate. Occasionally in Lisp programming you will need to pay
+attention to the difference.
+
address@hidden unibyte text
+ In unibyte representation, each character occupies one byte and
+therefore the possible character codes range from 0 to 255. Codes 0
+through 127 are @acronym{ASCII} characters; the codes from 128 through 255
+are used for one address@hidden character set (you can choose which
+character set by setting the variable @code{nonascii-insert-offset}).
+
address@hidden leading code
address@hidden multibyte text
address@hidden trailing codes
+ In multibyte representation, a character may occupy more than one
+byte, and as a result, the full range of Emacs character codes can be
+stored. The first byte of a multibyte character is always in the range
+128 through 159 (octal 0200 through 0237). These values are called
address@hidden codes}. The second and subsequent bytes of a multibyte
+character are always in the range 160 through 255 (octal 0240 through
+0377); these values are @dfn{trailing codes}.
+
+ Some sequences of bytes are not valid in multibyte text: for example,
+a single isolated byte in the range 128 through 159 is not allowed. But
+character codes 128 through 159 can appear in multibyte text,
+represented as two-byte sequences. All the character codes 128 through
+255 are possible (though slightly abnormal) in multibyte text; they
+appear in multibyte buffers and strings when you do explicit encoding
+and decoding (@pxref{Explicit Encoding}).
+
+ In a buffer, the buffer-local value of the variable
address@hidden specifies the representation used.
+The representation for a string is determined and recorded in the string
+when the string is constructed.
+
address@hidden enable-multibyte-characters
+This variable specifies the current buffer's text representation.
+If it is address@hidden, the buffer contains multibyte text; otherwise,
+it contains unibyte text.
+
+You cannot set this variable directly; instead, use the function
address@hidden to change a buffer's representation.
address@hidden defvar
+
address@hidden default-enable-multibyte-characters
+This variable's value is entirely equivalent to @code{(default-value
+'enable-multibyte-characters)}, and setting this variable changes that
+default value. Setting the local binding of
address@hidden in a specific buffer is not allowed,
+but changing the default value is supported, and it is a reasonable
+thing to do, because it has no effect on existing buffers.
+
+The @samp{--unibyte} command line option does its job by setting the
+default value to @code{nil} early in startup.
address@hidden defvar
+
address@hidden position-bytes position
+Return the byte-position corresponding to buffer position
address@hidden in the current buffer. This is 1 at the start of the
+buffer, and counts upward in bytes. If @var{position} is out of
+range, the value is @code{nil}.
address@hidden defun
+
address@hidden byte-to-position byte-position
+Return the buffer position corresponding to byte-position
address@hidden in the current buffer. If @var{byte-position} is
+out of range, the value is @code{nil}.
address@hidden defun
+
address@hidden multibyte-string-p string
+Return @code{t} if @var{string} is a multibyte string.
address@hidden defun
+
address@hidden string-bytes string
address@hidden string, number of bytes
+This function returns the number of bytes in @var{string}.
+If @var{string} is a multibyte string, this can be greater than
address@hidden(length @var{string})}.
address@hidden defun
+
address@hidden Converting Representations
address@hidden Converting Text Representations
+
+ Emacs can convert unibyte text to multibyte; it can also convert
+multibyte text to unibyte, though this conversion loses information. In
+general these conversions happen when inserting text into a buffer, or
+when putting text from several strings together in one string. You can
+also explicitly convert a string's contents to either representation.
+
+ Emacs chooses the representation for a string based on the text that
+it is constructed from. The general rule is to convert unibyte text to
+multibyte text when combining it with other multibyte text, because the
+multibyte representation is more general and can hold whatever
+characters the unibyte text has.
+
+ When inserting text into a buffer, Emacs converts the text to the
+buffer's representation, as specified by
address@hidden in that buffer. In particular, when
+you insert multibyte text into a unibyte buffer, Emacs converts the text
+to unibyte, even though this conversion cannot in general preserve all
+the characters that might be in the multibyte text. The other natural
+alternative, to convert the buffer contents to multibyte, is not
+acceptable because the buffer's representation is a choice made by the
+user that cannot be overridden automatically.
+
+ Converting unibyte text to multibyte text leaves @acronym{ASCII} characters
+unchanged, and likewise character codes 128 through 159. It converts
+the address@hidden codes 160 through 255 by adding the value
address@hidden to each character code. By setting this
+variable, you specify which character set the unibyte characters
+correspond to (@pxref{Character Sets}). For example, if
address@hidden is 2048, which is @code{(- (make-char
+'latin-iso8859-1) 128)}, then the unibyte address@hidden characters
+correspond to Latin 1. If it is 2688, which is @code{(- (make-char
+'greek-iso8859-7) 128)}, then they correspond to Greek letters.
+
+ Converting multibyte text to unibyte is simpler: it discards all but
+the low 8 bits of each character code. If @code{nonascii-insert-offset}
+has a reasonable value, corresponding to the beginning of some character
+set, this conversion is the inverse of the other: converting unibyte
+text to multibyte and back to unibyte reproduces the original unibyte
+text.
+
address@hidden nonascii-insert-offset
+This variable specifies the amount to add to a address@hidden character
+when converting unibyte text to multibyte. It also applies when
address@hidden inserts a character in the unibyte
address@hidden range, 128 through 255. However, the functions
address@hidden and @code{insert-char} do not perform this conversion.
+
+The right value to use to select character set @var{cs} is @code{(-
+(make-char @var{cs}) 128)}. If the value of
address@hidden is zero, then conversion actually uses the
+value for the Latin 1 character set, rather than zero.
address@hidden defvar
+
address@hidden nonascii-translation-table
+This variable provides a more general alternative to
address@hidden You can use it to specify independently
+how to translate each code in the range of 128 through 255 into a
+multibyte character. The value should be a char-table, or @code{nil}.
+If this is address@hidden, it overrides @code{nonascii-insert-offset}.
address@hidden defvar
+
+The next three functions either return the argument @var{string}, or a
+newly created string with no text properties.
+
address@hidden string-make-unibyte string
+This function converts the text of @var{string} to unibyte
+representation, if it isn't already, and returns the result. If
address@hidden is a unibyte string, it is returned unchanged. Multibyte
+character codes are converted to unibyte according to
address@hidden or, if that is @code{nil}, using
address@hidden If the lookup in the translation table
+fails, this function takes just the low 8 bits of each character.
address@hidden defun
+
address@hidden string-make-multibyte string
+This function converts the text of @var{string} to multibyte
+representation, if it isn't already, and returns the result. If
address@hidden is a multibyte string or consists entirely of
address@hidden characters, it is returned unchanged. In particular,
+if @var{string} is unibyte and entirely @acronym{ASCII}, the returned
+string is unibyte. (When the characters are all @acronym{ASCII},
+Emacs primitives will treat the string the same way whether it is
+unibyte or multibyte.) If @var{string} is unibyte and contains
address@hidden characters, the function
address@hidden is used to convert each unibyte
+character to a multibyte character.
address@hidden defun
+
address@hidden string-to-multibyte string
+This function returns a multibyte string containing the same sequence
+of character codes as @var{string}. Unlike
address@hidden, this function unconditionally returns a
+multibyte string. If @var{string} is a multibyte string, it is
+returned unchanged.
address@hidden defun
+
address@hidden multibyte-char-to-unibyte char
+This convert the multibyte character @var{char} to a unibyte
+character, based on @code{nonascii-translation-table} and
address@hidden
address@hidden defun
+
address@hidden unibyte-char-to-multibyte char
+This convert the unibyte character @var{char} to a multibyte
+character, based on @code{nonascii-translation-table} and
address@hidden
address@hidden defun
+
address@hidden Selecting a Representation
address@hidden Selecting a Representation
+
+ Sometimes it is useful to examine an existing buffer or string as
+multibyte when it was unibyte, or vice versa.
+
address@hidden set-buffer-multibyte multibyte
+Set the representation type of the current buffer. If @var{multibyte}
+is address@hidden, the buffer becomes multibyte. If @var{multibyte}
+is @code{nil}, the buffer becomes unibyte.
+
+This function leaves the buffer contents unchanged when viewed as a
+sequence of bytes. As a consequence, it can change the contents viewed
+as characters; a sequence of two bytes which is treated as one character
+in multibyte representation will count as two characters in unibyte
+representation. Character codes 128 through 159 are an exception. They
+are represented by one byte in a unibyte buffer, but when the buffer is
+set to multibyte, they are converted to two-byte sequences, and vice
+versa.
+
+This function sets @code{enable-multibyte-characters} to record which
+representation is in use. It also adjusts various data in the buffer
+(including overlays, text properties and markers) so that they cover the
+same text as they did before.
+
+You cannot use @code{set-buffer-multibyte} on an indirect buffer,
+because indirect buffers always inherit the representation of the
+base buffer.
address@hidden defun
+
address@hidden string-as-unibyte string
+This function returns a string with the same bytes as @var{string} but
+treating each byte as a character. This means that the value may have
+more characters than @var{string} has.
+
+If @var{string} is already a unibyte string, then the value is
address@hidden itself. Otherwise it is a newly created string, with no
+text properties. If @var{string} is multibyte, any characters it
+contains of charset @code{eight-bit-control} or @code{eight-bit-graphic}
+are converted to the corresponding single byte.
address@hidden defun
+
address@hidden string-as-multibyte string
+This function returns a string with the same bytes as @var{string} but
+treating each multibyte sequence as one character. This means that the
+value may have fewer characters than @var{string} has.
+
+If @var{string} is already a multibyte string, then the value is
address@hidden itself. Otherwise it is a newly created string, with no
+text properties. If @var{string} is unibyte and contains any individual
+8-bit bytes (i.e.@: not part of a multibyte form), they are converted to
+the corresponding multibyte character of charset @code{eight-bit-control}
+or @code{eight-bit-graphic}.
address@hidden defun
+
address@hidden Character Codes
address@hidden Character Codes
address@hidden character codes
+
+ The unibyte and multibyte text representations use different character
+codes. The valid character codes for unibyte representation range from
+0 to 255---the values that can fit in one byte. The valid character
+codes for multibyte representation range from 0 to 524287, but not all
+values in that range are valid. The values 128 through 255 are not
+entirely proper in multibyte text, but they can occur if you do explicit
+encoding and decoding (@pxref{Explicit Encoding}). Some other character
+codes cannot occur at all in multibyte text. Only the @acronym{ASCII} codes
+0 through 127 are completely legitimate in both representations.
+
address@hidden char-valid-p charcode &optional genericp
+This returns @code{t} if @var{charcode} is valid (either for unibyte
+text or for multibyte text).
+
address@hidden
+(char-valid-p 65)
+ @result{} t
+(char-valid-p 256)
+ @result{} nil
+(char-valid-p 2248)
+ @result{} t
address@hidden example
+
+If the optional argument @var{genericp} is address@hidden, this
+function also returns @code{t} if @var{charcode} is a generic
+character (@pxref{Splitting Characters}).
address@hidden defun
+
address@hidden Character Sets
address@hidden Character Sets
address@hidden character sets
+
+ Emacs classifies characters into various @dfn{character sets}, each of
+which has a name which is a symbol. Each character belongs to one and
+only one character set.
+
+ In general, there is one character set for each distinct script. For
+example, @code{latin-iso8859-1} is one character set,
address@hidden is another, and @code{ascii} is another. An
+Emacs character set can hold at most 9025 characters; therefore, in some
+cases, characters that would logically be grouped together are split
+into several character sets. For example, one set of Chinese
+characters, generally known as Big 5, is divided into two Emacs
+character sets, @code{chinese-big5-1} and @code{chinese-big5-2}.
+
+ @acronym{ASCII} characters are in character set @code{ascii}. The
address@hidden characters 128 through 159 are in character set
address@hidden, and codes 160 through 255 are in character set
address@hidden
+
address@hidden charsetp object
+Returns @code{t} if @var{object} is a symbol that names a character set,
address@hidden otherwise.
address@hidden defun
+
address@hidden charset-list
+The value is a list of all defined character set names.
address@hidden defvar
+
address@hidden charset-list
+This function returns the value of @code{charset-list}. It is only
+provided for backward compatibility.
address@hidden defun
+
address@hidden char-charset character
+This function returns the name of the character set that @var{character}
+belongs to, or the symbol @code{unknown} if @var{character} is not a
+valid character.
address@hidden defun
+
address@hidden charset-plist charset
+This function returns the charset property list of the character set
address@hidden Although @var{charset} is a symbol, this is not the same
+as the property list of that symbol. Charset properties are used for
+special purposes within Emacs.
address@hidden defun
+
address@hidden Command list-charset-chars charset
+This command displays a list of characters in the character set
address@hidden
address@hidden deffn
+
address@hidden Chars and Bytes
address@hidden Characters and Bytes
address@hidden bytes and characters
+
address@hidden introduction sequence (of character)
address@hidden dimension (of character set)
+ In multibyte representation, each character occupies one or more
+bytes. Each character set has an @dfn{introduction sequence}, which is
+normally one or two bytes long. (Exception: the @code{ascii} character
+set and the @code{eight-bit-graphic} character set have a zero-length
+introduction sequence.) The introduction sequence is the beginning of
+the byte sequence for any character in the character set. The rest of
+the character's bytes distinguish it from the other characters in the
+same character set. Depending on the character set, there are either
+one or two distinguishing bytes; the number of such bytes is called the
address@hidden of the character set.
+
address@hidden charset-dimension charset
+This function returns the dimension of @var{charset}; at present, the
+dimension is always 1 or 2.
address@hidden defun
+
address@hidden charset-bytes charset
+This function returns the number of bytes used to represent a character
+in character set @var{charset}.
address@hidden defun
+
+ This is the simplest way to determine the byte length of a character
+set's introduction sequence:
+
address@hidden
+(- (charset-bytes @var{charset})
+ (charset-dimension @var{charset}))
address@hidden example
+
address@hidden Splitting Characters
address@hidden Splitting Characters
address@hidden character as bytes
+
+ The functions in this section convert between characters and the byte
+values used to represent them. For most purposes, there is no need to
+be concerned with the sequence of bytes used to represent a character,
+because Emacs translates automatically when necessary.
+
address@hidden split-char character
+Return a list containing the name of the character set of
address@hidden, followed by one or two byte values (integers) which
+identify @var{character} within that character set. The number of byte
+values is the character set's dimension.
+
+If @var{character} is invalid as a character code, @code{split-char}
+returns a list consisting of the symbol @code{unknown} and @var{character}.
+
address@hidden
+(split-char 2248)
+ @result{} (latin-iso8859-1 72)
+(split-char 65)
+ @result{} (ascii 65)
+(split-char 128)
+ @result{} (eight-bit-control 128)
address@hidden example
address@hidden defun
+
address@hidden generate characters in charsets
address@hidden make-char charset &optional code1 code2
+This function returns the character in character set @var{charset} whose
+position codes are @var{code1} and @var{code2}. This is roughly the
+inverse of @code{split-char}. Normally, you should specify either one
+or both of @var{code1} and @var{code2} according to the dimension of
address@hidden For example,
+
address@hidden
+(make-char 'latin-iso8859-1 72)
+ @result{} 2248
address@hidden example
+
+Actually, the eighth bit of both @var{code1} and @var{code2} is zeroed
+before they are used to index @var{charset}. Thus you may use, for
+instance, an ISO 8859 character code rather than subtracting 128, as
+is necessary to index the corresponding Emacs charset.
address@hidden defun
+
address@hidden generic characters
+ If you call @code{make-char} with no @var{byte-values}, the result is
+a @dfn{generic character} which stands for @var{charset}. A generic
+character is an integer, but it is @emph{not} valid for insertion in the
+buffer as a character. It can be used in @code{char-table-range} to
+refer to the whole character set (@pxref{Char-Tables}).
address@hidden returns @code{nil} for generic characters.
+For example:
+
address@hidden
+(make-char 'latin-iso8859-1)
+ @result{} 2176
+(char-valid-p 2176)
+ @result{} nil
+(char-valid-p 2176 t)
+ @result{} t
+(split-char 2176)
+ @result{} (latin-iso8859-1 0)
address@hidden example
+
+The character sets @code{ascii}, @code{eight-bit-control}, and
address@hidden don't have corresponding generic characters. If
address@hidden is one of them and you don't supply @var{code1},
address@hidden returns the character code corresponding to the
+smallest code in @var{charset}.
+
address@hidden Scanning Charsets
address@hidden Scanning for Character Sets
+
+ Sometimes it is useful to find out which character sets appear in a
+part of a buffer or a string. One use for this is in determining which
+coding systems (@pxref{Coding Systems}) are capable of representing all
+of the text in question.
+
address@hidden charset-after &optional pos
+This function return the charset of a character in the current buffer
+at position @var{pos}. If @var{pos} is omitted or @code{nil}, it
+defaults to the current value of point. If @var{pos} is out of range,
+the value is @code{nil}.
address@hidden defun
+
address@hidden find-charset-region beg end &optional translation
+This function returns a list of the character sets that appear in the
+current buffer between positions @var{beg} and @var{end}.
+
+The optional argument @var{translation} specifies a translation table to
+be used in scanning the text (@pxref{Translation of Characters}). If it
+is address@hidden, then each character in the region is translated
+through this table, and the value returned describes the translated
+characters instead of the characters actually in the buffer.
address@hidden defun
+
address@hidden find-charset-string string &optional translation
+This function returns a list of the character sets that appear in the
+string @var{string}. It is just like @code{find-charset-region}, except
+that it applies to the contents of @var{string} instead of part of the
+current buffer.
address@hidden defun
+
address@hidden Translation of Characters
address@hidden Translation of Characters
address@hidden character translation tables
address@hidden translation tables
+
+ A @dfn{translation table} is a char-table that specifies a mapping
+of characters into characters. These tables are used in encoding and
+decoding, and for other purposes. Some coding systems specify their
+own particular translation tables; there are also default translation
+tables which apply to all other coding systems.
+
+ For instance, the coding-system @code{utf-8} has a translation table
+that maps characters of various charsets (e.g.,
address@hidden@var{x}}) into Unicode character sets. This way,
+it can encode Latin-2 characters into UTF-8. Meanwhile,
address@hidden operates by specifying
address@hidden to translate
address@hidden characters into corresponding Unicode characters.
+
address@hidden make-translation-table &rest translations
+This function returns a translation table based on the argument
address@hidden Each element of @var{translations} should be a
+list of elements of the form @code{(@var{from} . @var{to})}; this says
+to translate the character @var{from} into @var{to}.
+
+The arguments and the forms in each argument are processed in order,
+and if a previous form already translates @var{to} to some other
+character, say @var{to-alt}, @var{from} is also translated to
address@hidden
+
+You can also map one whole character set into another character set with
+the same dimension. To do this, you specify a generic character (which
+designates a character set) for @var{from} (@pxref{Splitting Characters}).
+In this case, if @var{to} is also a generic character, its character
+set should have the same dimension as @var{from}'s. Then the
+translation table translates each character of @var{from}'s character
+set into the corresponding character of @var{to}'s character set. If
address@hidden is a generic character and @var{to} is an ordinary
+character, then the translation table translates every character of
address@hidden's character set into @var{to}.
address@hidden defun
+
+ In decoding, the translation table's translations are applied to the
+characters that result from ordinary decoding. If a coding system has
+property @code{translation-table-for-decode}, that specifies the
+translation table to use. (This is a property of the coding system,
+as returned by @code{coding-system-get}, not a property of the symbol
+that is the coding system's name. @xref{Coding System Basics,, Basic
+Concepts of Coding Systems}.) Otherwise, if
address@hidden is address@hidden,
+decoding uses that table.
+
+ In encoding, the translation table's translations are applied to the
+characters in the buffer, and the result of translation is actually
+encoded. If a coding system has property
address@hidden, that specifies the translation
+table to use. Otherwise the variable
address@hidden specifies the translation
+table.
+
address@hidden standard-translation-table-for-decode
+This is the default translation table for decoding, for
+coding systems that don't specify any other translation table.
address@hidden defvar
+
address@hidden standard-translation-table-for-encode
+This is the default translation table for encoding, for
+coding systems that don't specify any other translation table.
address@hidden defvar
+
address@hidden translation-table-for-input
+Self-inserting characters are translated through this translation
+table before they are inserted. Search commands also translate their
+input through this table, so they can compare more reliably with
+what's in the buffer.
+
address@hidden sets this variable so that your
+keyboard input gets translated into the character sets that the buffer
+is likely to contain. This variable automatically becomes
+buffer-local when set.
address@hidden defvar
+
address@hidden Coding Systems
address@hidden Coding Systems
+
address@hidden coding system
+ When Emacs reads or writes a file, and when Emacs sends text to a
+subprocess or receives text from a subprocess, it normally performs
+character code conversion and end-of-line conversion as specified
+by a particular @dfn{coding system}.
+
+ How to define a coding system is an arcane matter, and is not
+documented here.
+
address@hidden
+* Coding System Basics:: Basic concepts.
+* Encoding and I/O:: How file I/O functions handle coding systems.
+* Lisp and Coding Systems:: Functions to operate on coding system names.
+* User-Chosen Coding Systems:: Asking the user to choose a coding system.
+* Default Coding Systems:: Controlling the default choices.
+* Specifying Coding Systems:: Requesting a particular coding system
+ for a single file operation.
+* Explicit Encoding:: Encoding or decoding text without doing I/O.
+* Terminal I/O Encoding:: Use of encoding for terminal I/O.
+* MS-DOS File Types:: How DOS "text" and "binary" files
+ relate to coding systems.
address@hidden menu
+
address@hidden Coding System Basics
address@hidden Basic Concepts of Coding Systems
+
address@hidden character code conversion
+ @dfn{Character code conversion} involves conversion between the encoding
+used inside Emacs and some other encoding. Emacs supports many
+different encodings, in that it can convert to and from them. For
+example, it can convert text to or from encodings such as Latin 1, Latin
+2, Latin 3, Latin 4, Latin 5, and several variants of ISO 2022. In some
+cases, Emacs supports several alternative encodings for the same
+characters; for example, there are three coding systems for the Cyrillic
+(Russian) alphabet: ISO, Alternativnyj, and KOI8.
+
+ Most coding systems specify a particular character code for
+conversion, but some of them leave the choice unspecified---to be chosen
+heuristically for each file, based on the data.
+
+ In general, a coding system doesn't guarantee roundtrip identity:
+decoding a byte sequence using coding system, then encoding the
+resulting text in the same coding system, can produce a different byte
+sequence. However, the following coding systems do guarantee that the
+byte sequence will be the same as what you originally decoded:
+
address@hidden
+chinese-big5 chinese-iso-8bit cyrillic-iso-8bit emacs-mule
+greek-iso-8bit hebrew-iso-8bit iso-latin-1 iso-latin-2 iso-latin-3
+iso-latin-4 iso-latin-5 iso-latin-8 iso-latin-9 iso-safe
+japanese-iso-8bit japanese-shift-jis korean-iso-8bit raw-text
address@hidden quotation
+
+ Encoding buffer text and then decoding the result can also fail to
+reproduce the original text. For instance, if you encode Latin-2
+characters with @code{utf-8} and decode the result using the same
+coding system, you'll get Unicode characters (of charset
address@hidden). If you encode Unicode characters with
address@hidden and decode the result with the same coding system,
+you'll get Latin-2 characters.
+
address@hidden EOL conversion
address@hidden end-of-line conversion
address@hidden line end conversion
+ @dfn{End of line conversion} handles three different conventions used
+on various systems for representing end of line in files. The Unix
+convention is to use the linefeed character (also called newline). The
+DOS convention is to use a carriage-return and a linefeed at the end of
+a line. The Mac convention is to use just carriage-return.
+
address@hidden base coding system
address@hidden variant coding system
+ @dfn{Base coding systems} such as @code{latin-1} leave the end-of-line
+conversion unspecified, to be chosen based on the data. @dfn{Variant
+coding systems} such as @code{latin-1-unix}, @code{latin-1-dos} and
address@hidden specify the end-of-line conversion explicitly as
+well. Most base coding systems have three corresponding variants whose
+names are formed by adding @samp{-unix}, @samp{-dos} and @samp{-mac}.
+
+ The coding system @code{raw-text} is special in that it prevents
+character code conversion, and causes the buffer visited with that
+coding system to be a unibyte buffer. It does not specify the
+end-of-line conversion, allowing that to be determined as usual by the
+data, and has the usual three variants which specify the end-of-line
+conversion. @code{no-conversion} is equivalent to @code{raw-text-unix}:
+it specifies no conversion of either character codes or end-of-line.
+
+ The coding system @code{emacs-mule} specifies that the data is
+represented in the internal Emacs encoding. This is like
address@hidden in that no code conversion happens, but different in
+that the result is multibyte data.
+
address@hidden coding-system-get coding-system property
+This function returns the specified property of the coding system
address@hidden Most coding system properties exist for internal
+purposes, but one that you might find useful is @code{mime-charset}.
+That property's value is the name used in MIME for the character coding
+which this coding system can read and write. Examples:
+
address@hidden
+(coding-system-get 'iso-latin-1 'mime-charset)
+ @result{} iso-8859-1
+(coding-system-get 'iso-2022-cn 'mime-charset)
+ @result{} iso-2022-cn
+(coding-system-get 'cyrillic-koi8 'mime-charset)
+ @result{} koi8-r
address@hidden example
+
+The value of the @code{mime-charset} property is also defined
+as an alias for the coding system.
address@hidden defun
+
address@hidden Encoding and I/O
address@hidden Encoding and I/O
+
+ The principal purpose of coding systems is for use in reading and
+writing files. The function @code{insert-file-contents} uses
+a coding system for decoding the file data, and @code{write-region}
+uses one to encode the buffer contents.
+
+ You can specify the coding system to use either explicitly
+(@pxref{Specifying Coding Systems}), or implicitly using a default
+mechanism (@pxref{Default Coding Systems}). But these methods may not
+completely specify what to do. For example, they may choose a coding
+system such as @code{undefined} which leaves the character code
+conversion to be determined from the data. In these cases, the I/O
+operation finishes the job of choosing a coding system. Very often
+you will want to find out afterwards which coding system was chosen.
+
address@hidden buffer-file-coding-system
+This buffer-local variable records the coding system that was used to visit
+the current buffer. It is used for saving the buffer, and for writing part
+of the buffer with @code{write-region}. If the text to be written
+cannot be safely encoded using the coding system specified by this
+variable, these operations select an alternative encoding by calling
+the function @code{select-safe-coding-system} (@pxref{User-Chosen
+Coding Systems}). If selecting a different encoding requires to ask
+the user to specify a coding system, @code{buffer-file-coding-system}
+is updated to the newly selected coding system.
+
address@hidden does @emph{not} affect sending text
+to a subprocess.
address@hidden defvar
+
address@hidden save-buffer-coding-system
+This variable specifies the coding system for saving the buffer (by
+overriding @code{buffer-file-coding-system}). Note that it is not used
+for @code{write-region}.
+
+When a command to save the buffer starts out to use
address@hidden (or @code{save-buffer-coding-system}),
+and that coding system cannot handle
+the actual text in the buffer, the command asks the user to choose
+another coding system (by calling @code{select-safe-coding-system}).
+After that happens, the command also updates
address@hidden to represent the coding system that
+the user specified.
address@hidden defvar
+
address@hidden last-coding-system-used
+I/O operations for files and subprocesses set this variable to the
+coding system name that was used. The explicit encoding and decoding
+functions (@pxref{Explicit Encoding}) set it too.
+
address@hidden:} Since receiving subprocess output sets this variable,
+it can change whenever Emacs waits; therefore, you should copy the
+value shortly after the function call that stores the value you are
+interested in.
address@hidden defvar
+
+ The variable @code{selection-coding-system} specifies how to encode
+selections for the window system. @xref{Window System Selections}.
+
address@hidden file-name-coding-system
+The variable @code{file-name-coding-system} specifies the coding
+system to use for encoding file names. Emacs encodes file names using
+that coding system for all file operations. If
address@hidden is @code{nil}, Emacs uses a default
+coding system determined by the selected language environment. In the
+default language environment, any address@hidden characters in
+file names are not encoded specially; they appear in the file system
+using the internal Emacs representation.
address@hidden defvar
+
+ @strong{Warning:} if you change @code{file-name-coding-system} (or
+the language environment) in the middle of an Emacs session, problems
+can result if you have already visited files whose names were encoded
+using the earlier coding system and are handled differently under the
+new coding system. If you try to save one of these buffers under the
+visited file name, saving may use the wrong file name, or it may get
+an error. If such a problem happens, use @kbd{C-x C-w} to specify a
+new file name for that buffer.
+
address@hidden Lisp and Coding Systems
address@hidden Coding Systems in Lisp
+
+ Here are the Lisp facilities for working with coding systems:
+
address@hidden coding-system-list &optional base-only
+This function returns a list of all coding system names (symbols). If
address@hidden is address@hidden, the value includes only the
+base coding systems. Otherwise, it includes alias and variant coding
+systems as well.
address@hidden defun
+
address@hidden coding-system-p object
+This function returns @code{t} if @var{object} is a coding system
+name or @code{nil}.
address@hidden defun
+
address@hidden check-coding-system coding-system
+This function checks the validity of @var{coding-system}.
+If that is valid, it returns @var{coding-system}.
+Otherwise it signals an error with condition @code{coding-system-error}.
address@hidden defun
+
address@hidden coding-system-eol-type coding-system
+This function returns the type of end-of-line (a.k.a.@: @dfn{eol})
+conversion used by @var{coding-system}. If @var{coding-system}
+specifies a certain eol conversion, the return value is an integer 0,
+1, or 2, standing for @code{unix}, @code{dos}, and @code{mac},
+respectively. If @var{coding-system} doesn't specify eol conversion
+explicitly, the return value is a vector of coding systems, each one
+with one of the possible eol conversion types, like this:
+
address@hidden
+(coding-system-eol-type 'latin-1)
+ @result{} [latin-1-unix latin-1-dos latin-1-mac]
address@hidden lisp
+
address@hidden
+If this function returns a vector, Emacs will decide, as part of the
+text encoding or decoding process, what eol conversion to use. For
+decoding, the end-of-line format of the text is auto-detected, and the
+eol conversion is set to match it (e.g., DOS-style CRLF format will
+imply @code{dos} eol conversion). For encoding, the eol conversion is
+taken from the appropriate default coding system (e.g.,
address@hidden for
address@hidden), or from the default eol conversion
+appropriate for the underlying platform.
address@hidden defun
+
address@hidden coding-system-change-eol-conversion coding-system eol-type
+This function returns a coding system which is like @var{coding-system}
+except for its eol conversion, which is specified by @code{eol-type}.
address@hidden should be @code{unix}, @code{dos}, @code{mac}, or
address@hidden If it is @code{nil}, the returned coding system determines
+the end-of-line conversion from the data.
+
address@hidden may also be 0, 1 or 2, standing for @code{unix},
address@hidden and @code{mac}, respectively.
address@hidden defun
+
address@hidden coding-system-change-text-conversion eol-coding text-coding
+This function returns a coding system which uses the end-of-line
+conversion of @var{eol-coding}, and the text conversion of
address@hidden If @var{text-coding} is @code{nil}, it returns
address@hidden, or one of its variants according to @var{eol-coding}.
address@hidden defun
+
address@hidden find-coding-systems-region from to
+This function returns a list of coding systems that could be used to
+encode a text between @var{from} and @var{to}. All coding systems in
+the list can safely encode any multibyte characters in that portion of
+the text.
+
+If the text contains no multibyte characters, the function returns the
+list @code{(undecided)}.
address@hidden defun
+
address@hidden find-coding-systems-string string
+This function returns a list of coding systems that could be used to
+encode the text of @var{string}. All coding systems in the list can
+safely encode any multibyte characters in @var{string}. If the text
+contains no multibyte characters, this returns the list
address@hidden(undecided)}.
address@hidden defun
+
address@hidden find-coding-systems-for-charsets charsets
+This function returns a list of coding systems that could be used to
+encode all the character sets in the list @var{charsets}.
address@hidden defun
+
address@hidden detect-coding-region start end &optional highest
+This function chooses a plausible coding system for decoding the text
+from @var{start} to @var{end}. This text should be a byte sequence
+(@pxref{Explicit Encoding}).
+
+Normally this function returns a list of coding systems that could
+handle decoding the text that was scanned. They are listed in order of
+decreasing priority. But if @var{highest} is address@hidden, then the
+return value is just one coding system, the one that is highest in
+priority.
+
+If the region contains only @acronym{ASCII} characters except for such
+ISO-2022 control characters ISO-2022 as @code{ESC}, the value is
address@hidden or @code{(undecided)}, or a variant specifying
+end-of-line conversion, if that can be deduced from the text.
address@hidden defun
+
address@hidden detect-coding-string string &optional highest
+This function is like @code{detect-coding-region} except that it
+operates on the contents of @var{string} instead of bytes in the buffer.
address@hidden defun
+
+ @xref{Coding systems for a subprocess,, Process Information}, in
+particular the description of the functions
address@hidden and @code{set-process-coding-system}, for
+how to examine or set the coding systems used for I/O to a subprocess.
+
address@hidden User-Chosen Coding Systems
address@hidden User-Chosen Coding Systems
+
address@hidden select safe coding system
address@hidden select-safe-coding-system from to &optional
default-coding-system accept-default-p file
+This function selects a coding system for encoding specified text,
+asking the user to choose if necessary. Normally the specified text
+is the text in the current buffer between @var{from} and @var{to}. If
address@hidden is a string, the string specifies the text to encode, and
address@hidden is ignored.
+
+If @var{default-coding-system} is address@hidden, that is the first
+coding system to try; if that can handle the text,
address@hidden returns that coding system. It can
+also be a list of coding systems; then the function tries each of them
+one by one. After trying all of them, it next tries the current
+buffer's value of @code{buffer-file-coding-system} (if it is not
address@hidden), then the value of
address@hidden and finally the user's most
+preferred coding system, which the user can set using the command
address@hidden (@pxref{Recognize Coding,, Recognizing
+Coding Systems, emacs, The GNU Emacs Manual}).
+
+If one of those coding systems can safely encode all the specified
+text, @code{select-safe-coding-system} chooses it and returns it.
+Otherwise, it asks the user to choose from a list of coding systems
+which can encode all the text, and returns the user's choice.
+
address@hidden can also be a list whose first element is
+t and whose other elements are coding systems. Then, if no coding
+system in the list can handle the text, @code{select-safe-coding-system}
+queries the user immediately, without trying any of the three
+alternatives described above.
+
+The optional argument @var{accept-default-p}, if address@hidden,
+should be a function to determine whether a coding system selected
+without user interaction is acceptable. @code{select-safe-coding-system}
+calls this function with one argument, the base coding system of the
+selected coding system. If @var{accept-default-p} returns @code{nil},
address@hidden rejects the silently selected coding
+system, and asks the user to select a coding system from a list of
+possible candidates.
+
address@hidden select-safe-coding-system-accept-default-p
+If the variable @code{select-safe-coding-system-accept-default-p} is
address@hidden, its value overrides the value of
address@hidden
+
+As a final step, before returning the chosen coding system,
address@hidden checks whether that coding system is
+consistent with what would be selected if the contents of the region
+were read from a file. (If not, this could lead to data corruption in
+a file subsequently re-visited and edited.) Normally,
address@hidden uses @code{buffer-file-name} as the
+file for this purpose, but if @var{file} is address@hidden, it uses
+that file instead (this can be relevant for @code{write-region} and
+similar functions). If it detects an apparent inconsistency,
address@hidden queries the user before selecting the
+coding system.
address@hidden defun
+
+ Here are two functions you can use to let the user specify a coding
+system, with completion. @xref{Completion}.
+
address@hidden read-coding-system prompt &optional default
+This function reads a coding system using the minibuffer, prompting with
+string @var{prompt}, and returns the coding system name as a symbol. If
+the user enters null input, @var{default} specifies which coding system
+to return. It should be a symbol or a string.
address@hidden defun
+
address@hidden read-non-nil-coding-system prompt
+This function reads a coding system using the minibuffer, prompting with
+string @var{prompt}, and returns the coding system name as a symbol. If
+the user tries to enter null input, it asks the user to try again.
address@hidden Systems}.
address@hidden defun
+
address@hidden Default Coding Systems
address@hidden Default Coding Systems
+
+ This section describes variables that specify the default coding
+system for certain files or when running certain subprograms, and the
+function that I/O operations use to access them.
+
+ The idea of these variables is that you set them once and for all to the
+defaults you want, and then do not change them again. To specify a
+particular coding system for a particular operation in a Lisp program,
+don't change these variables; instead, override them using
address@hidden and @code{coding-system-for-write}
+(@pxref{Specifying Coding Systems}).
+
address@hidden auto-coding-regexp-alist
+This variable is an alist of text patterns and corresponding coding
+systems. Each element has the form @code{(@var{regexp}
+. @var{coding-system})}; a file whose first few kilobytes match
address@hidden is decoded with @var{coding-system} when its contents are
+read into a buffer. The settings in this alist take priority over
address@hidden:} tags in the files and the contents of
address@hidden (see below). The default value is set
+so that Emacs automatically recognizes mail files in Babyl format and
+reads them with no code conversions.
address@hidden defvar
+
address@hidden file-coding-system-alist
+This variable is an alist that specifies the coding systems to use for
+reading and writing particular files. Each element has the form
address@hidden(@var{pattern} . @var{coding})}, where @var{pattern} is a regular
+expression that matches certain file names. The element applies to file
+names that match @var{pattern}.
+
+The @sc{cdr} of the element, @var{coding}, should be either a coding
+system, a cons cell containing two coding systems, or a function name (a
+symbol with a function definition). If @var{coding} is a coding system,
+that coding system is used for both reading the file and writing it. If
address@hidden is a cons cell containing two coding systems, its @sc{car}
+specifies the coding system for decoding, and its @sc{cdr} specifies the
+coding system for encoding.
+
+If @var{coding} is a function name, the function should take one
+argument, a list of all arguments passed to
address@hidden It must return a coding system
+or a cons cell containing two coding systems. This value has the same
+meaning as described above.
+
+If @var{coding} (or what returned by the above function) is
address@hidden, the normal code-detection is performed.
address@hidden defvar
+
address@hidden process-coding-system-alist
+This variable is an alist specifying which coding systems to use for a
+subprocess, depending on which program is running in the subprocess. It
+works like @code{file-coding-system-alist}, except that @var{pattern} is
+matched against the program name used to start the subprocess. The coding
+system or systems specified in this alist are used to initialize the
+coding systems used for I/O to the subprocess, but you can specify
+other coding systems later using @code{set-process-coding-system}.
address@hidden defvar
+
+ @strong{Warning:} Coding systems such as @code{undecided}, which
+determine the coding system from the data, do not work entirely reliably
+with asynchronous subprocess output. This is because Emacs handles
+asynchronous subprocess output in batches, as it arrives. If the coding
+system leaves the character code conversion unspecified, or leaves the
+end-of-line conversion unspecified, Emacs must try to detect the proper
+conversion from one batch at a time, and this does not always work.
+
+ Therefore, with an asynchronous subprocess, if at all possible, use a
+coding system which determines both the character code conversion and
+the end of line conversion---that is, one like @code{latin-1-unix},
+rather than @code{undecided} or @code{latin-1}.
+
address@hidden network-coding-system-alist
+This variable is an alist that specifies the coding system to use for
+network streams. It works much like @code{file-coding-system-alist},
+with the difference that the @var{pattern} in an element may be either a
+port number or a regular expression. If it is a regular expression, it
+is matched against the network service name used to open the network
+stream.
address@hidden defvar
+
address@hidden default-process-coding-system
+This variable specifies the coding systems to use for subprocess (and
+network stream) input and output, when nothing else specifies what to
+do.
+
+The value should be a cons cell of the form @code{(@var{input-coding}
+. @var{output-coding})}. Here @var{input-coding} applies to input from
+the subprocess, and @var{output-coding} applies to output to it.
address@hidden defvar
+
address@hidden auto-coding-functions
+This variable holds a list of functions that try to determine a
+coding system for a file based on its undecoded contents.
+
+Each function in this list should be written to look at text in the
+current buffer, but should not modify it in any way. The buffer will
+contain undecoded text of parts of the file. Each function should
+take one argument, @var{size}, which tells it how many characters to
+look at, starting from point. If the function succeeds in determining
+a coding system for the file, it should return that coding system.
+Otherwise, it should return @code{nil}.
+
+If a file has a @samp{coding:} tag, that takes precedence, so these
+functions won't be called.
address@hidden defvar
+
address@hidden find-operation-coding-system operation &rest arguments
+This function returns the coding system to use (by default) for
+performing @var{operation} with @var{arguments}. The value has this
+form:
+
address@hidden
+(@var{decoding-system} . @var{encoding-system})
address@hidden example
+
+The first element, @var{decoding-system}, is the coding system to use
+for decoding (in case @var{operation} does decoding), and
address@hidden is the coding system for encoding (in case
address@hidden does encoding).
+
+The argument @var{operation} is a symbol, one of @code{write-region},
address@hidden, @code{call-process}, @code{call-process-region},
address@hidden, or @code{open-network-stream}. These are
+the names of the Emacs I/O primitives that can do character code and
+eol conversion.
+
+The remaining arguments should be the same arguments that might be given
+to the corresponding I/O primitive. Depending on the primitive, one
+of those arguments is selected as the @dfn{target}. For example, if
address@hidden does file I/O, whichever argument specifies the file
+name is the target. For subprocess primitives, the process name is the
+target. For @code{open-network-stream}, the target is the service name
+or port number.
+
+Depending on @var{operation}, this function looks up the target in
address@hidden, @code{process-coding-system-alist},
+or @code{network-coding-system-alist}. If the target is found in the
+alist, @code{find-operation-coding-system} returns its association in
+the alist; otherwise it returns @code{nil}.
+
+If @var{operation} is @code{insert-file-contents}, the argument
+corresponding to the target may be a cons cell of the form
address@hidden(@var{filename} . @var{buffer})}). In that case, @var{filename}
+is a file name to look up in @code{file-coding-system-alist}, and
address@hidden is a buffer that contains the file's contents (not yet
+decoded). If @code{file-coding-system-alist} specifies a function to
+call for this file, and that function needs to examine the file's
+contents (as it usually does), it should examine the contents of
address@hidden instead of reading the file.
address@hidden defun
+
address@hidden Specifying Coding Systems
address@hidden Specifying a Coding System for One Operation
+
+ You can specify the coding system for a specific operation by binding
+the variables @code{coding-system-for-read} and/or
address@hidden
+
address@hidden coding-system-for-read
+If this variable is address@hidden, it specifies the coding system to
+use for reading a file, or for input from a synchronous subprocess.
+
+It also applies to any asynchronous subprocess or network stream, but in
+a different way: the value of @code{coding-system-for-read} when you
+start the subprocess or open the network stream specifies the input
+decoding method for that subprocess or network stream. It remains in
+use for that subprocess or network stream unless and until overridden.
+
+The right way to use this variable is to bind it with @code{let} for a
+specific I/O operation. Its global value is normally @code{nil}, and
+you should not globally set it to any other value. Here is an example
+of the right way to use the variable:
+
address@hidden
+;; @r{Read the file with no character code conversion.}
+;; @r{Assume @acronym{crlf} represents end-of-line.}
+(let ((coding-system-for-read 'emacs-mule-dos))
+ (insert-file-contents filename))
address@hidden example
+
+When its value is address@hidden, this variable takes precedence over
+all other methods of specifying a coding system to use for input,
+including @code{file-coding-system-alist},
address@hidden and
address@hidden
address@hidden defvar
+
address@hidden coding-system-for-write
+This works much like @code{coding-system-for-read}, except that it
+applies to output rather than input. It affects writing to files,
+as well as sending output to subprocesses and net connections.
+
+When a single operation does both input and output, as do
address@hidden and @code{start-process}, both
address@hidden and @code{coding-system-for-write}
+affect it.
address@hidden defvar
+
address@hidden inhibit-eol-conversion
+When this variable is address@hidden, no end-of-line conversion is done,
+no matter which coding system is specified. This applies to all the
+Emacs I/O and subprocess primitives, and to the explicit encoding and
+decoding functions (@pxref{Explicit Encoding}).
address@hidden defvar
+
address@hidden Explicit Encoding
address@hidden Explicit Encoding and Decoding
address@hidden encoding in coding systems
address@hidden decoding in coding systems
+
+ All the operations that transfer text in and out of Emacs have the
+ability to use a coding system to encode or decode the text.
+You can also explicitly encode and decode text using the functions
+in this section.
+
+ The result of encoding, and the input to decoding, are not ordinary
+text. They logically consist of a series of byte values; that is, a
+series of characters whose codes are in the range 0 through 255. In a
+multibyte buffer or string, character codes 128 through 159 are
+represented by multibyte sequences, but this is invisible to Lisp
+programs.
+
+ The usual way to read a file into a buffer as a sequence of bytes, so
+you can decode the contents explicitly, is with
address@hidden (@pxref{Reading from Files});
+alternatively, specify a address@hidden @var{rawfile} argument when
+visiting a file with @code{find-file-noselect}. These methods result in
+a unibyte buffer.
+
+ The usual way to use the byte sequence that results from explicitly
+encoding text is to copy it to a file or process---for example, to write
+it with @code{write-region} (@pxref{Writing to Files}), and suppress
+encoding by binding @code{coding-system-for-write} to
address@hidden
+
+ Here are the functions to perform explicit encoding or decoding. The
+encoding functions produce sequences of bytes; the decoding functions
+are meant to operate on sequences of bytes. All of these functions
+discard text properties.
+
address@hidden Command encode-coding-region start end coding-system
+This command encodes the text from @var{start} to @var{end} according
+to coding system @var{coding-system}. The encoded text replaces the
+original text in the buffer. The result of encoding is logically a
+sequence of bytes, but the buffer remains multibyte if it was multibyte
+before.
+
+This command returns the length of the encoded text.
address@hidden deffn
+
address@hidden encode-coding-string string coding-system &optional nocopy
+This function encodes the text in @var{string} according to coding
+system @var{coding-system}. It returns a new string containing the
+encoded text, except when @var{nocopy} is address@hidden, in which
+case the function may return @var{string} itself if the encoding
+operation is trivial. The result of encoding is a unibyte string.
address@hidden defun
+
address@hidden Command decode-coding-region start end coding-system
+This command decodes the text from @var{start} to @var{end} according
+to coding system @var{coding-system}. The decoded text replaces the
+original text in the buffer. To make explicit decoding useful, the text
+before decoding ought to be a sequence of byte values, but both
+multibyte and unibyte buffers are acceptable.
+
+This command returns the length of the decoded text.
address@hidden deffn
+
address@hidden decode-coding-string string coding-system &optional nocopy
+This function decodes the text in @var{string} according to coding
+system @var{coding-system}. It returns a new string containing the
+decoded text, except when @var{nocopy} is address@hidden, in which
+case the function may return @var{string} itself if the decoding
+operation is trivial. To make explicit decoding useful, the contents
+of @var{string} ought to be a sequence of byte values, but a multibyte
+string is acceptable.
address@hidden defun
+
address@hidden decode-coding-inserted-region from to filename &optional visit
beg end replace
+This function decodes the text from @var{from} to @var{to} as if
+it were being read from file @var{filename} using @code{insert-file-contents}
+using the rest of the arguments provided.
+
+The normal way to use this function is after reading text from a file
+without decoding, if you decide you would rather have decoded it.
+Instead of deleting the text and reading it again, this time with
+decoding, you can call this function.
address@hidden defun
+
address@hidden Terminal I/O Encoding
address@hidden Terminal I/O Encoding
+
+ Emacs can decode keyboard input using a coding system, and encode
+terminal output. This is useful for terminals that transmit or display
+text using a particular encoding such as Latin-1. Emacs does not set
address@hidden for encoding or decoding for the
+terminal.
+
address@hidden keyboard-coding-system
+This function returns the coding system that is in use for decoding
+keyboard input---or @code{nil} if no coding system is to be used.
address@hidden defun
+
address@hidden Command set-keyboard-coding-system coding-system
+This command specifies @var{coding-system} as the coding system to
+use for decoding keyboard input. If @var{coding-system} is @code{nil},
+that means do not decode keyboard input.
address@hidden deffn
+
address@hidden terminal-coding-system
+This function returns the coding system that is in use for encoding
+terminal output---or @code{nil} for no encoding.
address@hidden defun
+
address@hidden Command set-terminal-coding-system coding-system
+This command specifies @var{coding-system} as the coding system to use
+for encoding terminal output. If @var{coding-system} is @code{nil},
+that means do not encode terminal output.
address@hidden deffn
+
address@hidden MS-DOS File Types
address@hidden MS-DOS File Types
address@hidden DOS file types
address@hidden MS-DOS file types
address@hidden Windows file types
address@hidden file types on MS-DOS and Windows
address@hidden text files and binary files
address@hidden binary files and text files
+
+ On MS-DOS and Microsoft Windows, Emacs guesses the appropriate
+end-of-line conversion for a file by looking at the file's name. This
+feature classifies files as @dfn{text files} and @dfn{binary files}. By
+``binary file'' we mean a file of literal byte values that are not
+necessarily meant to be characters; Emacs does no end-of-line conversion
+and no character code conversion for them. On the other hand, the bytes
+in a text file are intended to represent characters; when you create a
+new file whose name implies that it is a text file, Emacs uses DOS
+end-of-line conversion.
+
address@hidden buffer-file-type
+This variable, automatically buffer-local in each buffer, records the
+file type of the buffer's visited file. When a buffer does not specify
+a coding system with @code{buffer-file-coding-system}, this variable is
+used to determine which coding system to use when writing the contents
+of the buffer. It should be @code{nil} for text, @code{t} for binary.
+If it is @code{t}, the coding system is @code{no-conversion}.
+Otherwise, @code{undecided-dos} is used.
+
+Normally this variable is set by visiting a file; it is set to
address@hidden if the file was visited without any actual conversion.
address@hidden defvar
+
address@hidden file-name-buffer-file-type-alist
+This variable holds an alist for recognizing text and binary files.
+Each element has the form (@var{regexp} . @var{type}), where
address@hidden is matched against the file name, and @var{type} may be
address@hidden for text, @code{t} for binary, or a function to call to
+compute which. If it is a function, then it is called with a single
+argument (the file name) and should return @code{t} or @code{nil}.
+
+When running on MS-DOS or MS-Windows, Emacs checks this alist to decide
+which coding system to use when reading a file. For a text file,
address@hidden is used. For a binary file, @code{no-conversion}
+is used.
+
+If no element in this alist matches a given file name, then
address@hidden says how to treat the file.
address@hidden defopt
+
address@hidden default-buffer-file-type
+This variable says how to handle files for which
address@hidden says nothing about the type.
+
+If this variable is address@hidden, then these files are treated as
+binary: the coding system @code{no-conversion} is used. Otherwise,
+nothing special is done for them---the coding system is deduced solely
+from the file contents, in the usual Emacs fashion.
address@hidden defopt
+
address@hidden Input Methods
address@hidden Input Methods
address@hidden input methods
+
+ @dfn{Input methods} provide convenient ways of entering address@hidden
+characters from the keyboard. Unlike coding systems, which translate
address@hidden characters to and from encodings meant to be read by
+programs, input methods provide human-friendly commands. (@xref{Input
+Methods,,, emacs, The GNU Emacs Manual}, for information on how users
+use input methods to enter text.) How to define input methods is not
+yet documented in this manual, but here we describe how to use them.
+
+ Each input method has a name, which is currently a string;
+in the future, symbols may also be usable as input method names.
+
address@hidden current-input-method
+This variable holds the name of the input method now active in the
+current buffer. (It automatically becomes local in each buffer when set
+in any fashion.) It is @code{nil} if no input method is active in the
+buffer now.
address@hidden defvar
+
address@hidden default-input-method
+This variable holds the default input method for commands that choose an
+input method. Unlike @code{current-input-method}, this variable is
+normally global.
address@hidden defopt
+
address@hidden Command set-input-method input-method
+This command activates input method @var{input-method} for the current
+buffer. It also sets @code{default-input-method} to @var{input-method}.
+If @var{input-method} is @code{nil}, this command deactivates any input
+method for the current buffer.
address@hidden deffn
+
address@hidden read-input-method-name prompt &optional default inhibit-null
+This function reads an input method name with the minibuffer, prompting
+with @var{prompt}. If @var{default} is address@hidden, that is returned
+by default, if the user enters empty input. However, if
address@hidden is address@hidden, empty input signals an error.
+
+The returned value is a string.
address@hidden defun
+
address@hidden input-method-alist
+This variable defines all the supported input methods.
+Each element defines one input method, and should have the form:
+
address@hidden
+(@var{input-method} @var{language-env} @var{activate-func}
+ @var{title} @var{description} @var{args}...)
address@hidden example
+
+Here @var{input-method} is the input method name, a string;
address@hidden is another string, the name of the language
+environment this input method is recommended for. (That serves only for
+documentation purposes.)
+
address@hidden is a function to call to activate this method. The
address@hidden, if any, are passed as arguments to @var{activate-func}. All
+told, the arguments to @var{activate-func} are @var{input-method} and
+the @var{args}.
+
address@hidden is a string to display in the mode line while this method is
+active. @var{description} is a string describing this method and what
+it is good for.
address@hidden defvar
+
+ The fundamental interface to input methods is through the
+variable @code{input-method-function}. @xref{Reading One Event},
+and @ref{Invoking the Input Method}.
+
address@hidden Locales
address@hidden Locales
address@hidden locale
+
+ POSIX defines a concept of ``locales'' which control which language
+to use in language-related features. These Emacs variables control
+how Emacs interacts with these features.
+
address@hidden locale-coding-system
address@hidden keyboard input decoding on X
+This variable specifies the coding system to use for decoding system
+error messages and---on X Window system only---keyboard input, for
+encoding the format argument to @code{format-time-string}, and for
+decoding the return value of @code{format-time-string}.
address@hidden defvar
+
address@hidden system-messages-locale
+This variable specifies the locale to use for generating system error
+messages. Changing the locale can cause messages to come out in a
+different language or in a different orthography. If the variable is
address@hidden, the locale is specified by environment variables in the
+usual POSIX fashion.
address@hidden defvar
+
address@hidden system-time-locale
+This variable specifies the locale to use for formatting time values.
+Changing the locale can cause messages to appear according to the
+conventions of a different language. If the variable is @code{nil}, the
+locale is specified by environment variables in the usual POSIX fashion.
address@hidden defvar
+
address@hidden locale-info item
+This function returns locale data @var{item} for the current POSIX
+locale, if available. @var{item} should be one of these symbols:
+
address@hidden @code
address@hidden codeset
+Return the character set as a string (locale item @code{CODESET}).
+
address@hidden days
+Return a 7-element vector of day names (locale items
address@hidden through @code{DAY_7});
+
address@hidden months
+Return a 12-element vector of month names (locale items @code{MON_1}
+through @code{MON_12}).
+
address@hidden paper
+Return a list @code{(@var{width} @var{height})} for the default paper
+size measured in millimeters (locale items @code{PAPER_WIDTH} and
address@hidden).
address@hidden table
+
+If the system can't provide the requested information, or if
address@hidden is not one of those symbols, the value is @code{nil}. All
+strings in the return value are decoded using
address@hidden @xref{Locales,,, libc, The GNU Libc Manual},
+for more information about locales and locale items.
address@hidden defun
+
address@hidden
+ arch-tag: be705bf8-941b-4c35-84fc-ad7d20ddb7cb
address@hidden ignore