Shift JIS

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Shift JIS (also SJIS, MIME name Shift_JIS) is a character encoding for the Japanese language originally developed by a Japanese company called ASCII Corporation in conjunction with Microsoft and standardized as JIS X 0208 Appendix 1. It is based on character sets defined within JIS standards JIS X 0201:1997 (for the single-byte characters) and JIS X 0208:1997 (for the double byte characters). The lead bytes for the double byte characters are "shifted" around the 64 halfwidth katakana characters in the single-byte range 0xA1 to 0xDF. The single-byte characters 0x00 to 0x7F match the ASCII encoding, except for a yen sign at 0x5C and an overline at 0x7E in place of the ASCII character set's backslash and tilde respectively. On the web, 0x5C is still used as the JavaScript escape character. The single-byte characters from 0xA1 to 0xDF map to the half-width katakana characters found in JIS X 0201.

Shift JIS requires an 8-bit medium for transmission. It is fully backwards compatible with the legacy JIS X 0201 single-byte encoding, meaning it supports half-width katakana and that any valid JIS X 0201 string is also a valid Shift JIS string. However Shift JIS only guarantees that the first byte will be in the upper ASCII range; the value of the second byte can be either high or low. This makes reliable Shift JIS detection difficult. On the other hand, the competing 8-bit format EUC-JP, which does not support single-byte halfwidth katakana, allows for a much cleaner and direct conversion to and from JIS X 0208 codepoints, as all upper-ASCII bytes are part of a double-byte character and all lower-ASCII bytes are part of a single-byte character.

For a double-byte JIS sequence $j 1 j 2$ , the transformation to the corresponding Shift JIS bytes $s 1 s 2$ is:

$33 \le j_1 \le 94 \Rightarrow s_1 = \left \lfloor \frac{j_1 + 1}{2} \right \rfloor + 112\,$

$95 \le j_1 \le 126 \Rightarrow s_1 = \left \lfloor \frac{j_1 + 1}{2} \right \rfloor + 176\,$

$j_1 \mbox{ is odd } \Rightarrow s_2 = j_2 + 31 + \begin{cases} 1 & \mbox{if }j_2 \ge 96 \\ 0 & \mbox{otherwise} \end{cases} \,$

$j_1 \mbox{ is even } \Rightarrow s_2 = j_2 + 126\,$

Many different versions of Shift JIS exist. There are two areas for expansion: Firstly, JIS X 0208 does not fill the whole 94×94 space encoded for it in Shift JIS, therefore there is room for more characters here — these are really extensions to JIS X 0208 rather than to Shift JIS itself. The most popular extension here is to the Windows-31J (otherwise known as Code page 932) encoding popularized by Microsoft, although Microsoft itself does not recognize the Windows-31J name and instead calls that variation "shift_jis". Secondly, Shift JIS has more encoding space than is needed for JIS X 0201 and JIS X 0208, and this space can and is used for yet more characters. The space with lead bytes 0xF5 to 0xF9 is used by Japanese mobile phone operators for pictographs for use in E-mail, for example (KDDI goes further and defines hundreds more in the space with lead bytes 0xF3 and 0xF4).

Beyond even this there have been numerous minor variations made on Shift JIS, with individual characters here and there altered. Most of these extensions and variants have no IANA registration, so there is much scope for confusion if the extensions are used. Microsoft Code Page 932 is registered separately from Shift JIS.

IBM CCSID 943 has the same extensions as Code Page 932.

As with most code pages and encodings it is recommended that Unicode be used instead.

[edit] Shift JIS byte map

The chart below gives the detailed meaning of each byte in a Shift JIS encoded stream.

First byte
	0	1	2	3	4	5	6	7	8	9	A	B	C	D	E	F
0	NUL	SOH	STX	ETX	EOT	ENQ	ACK	BEL	BS	HT	LF	VT	FF	CR	SO	SI
1	DLE	DC1	DC2	DC3	DC4	NAK	SYN	ETB	CAN	EM	SUB	ESC	FS	GS	RS	US
2		!	"	#	$	%	&	'	(	)	*	+	,	-	.	/
3	0	1	2	3	4	5	6	7	8	9	:	;	<	=	>	?
4	@	A	B	C	D	E	F	G	H	I	J	K	L	M	N	O
5	P	Q	R	S	T	U	V	W	X	Y	Z	[	¥	]	^	_
6	`	a	b	c	d	e	f	g	h	i	j	k	l	m	n	o
7	p	q	r	s	t	u	v	w	x	y	z	{	\|	}	‾	DEL
8
9
A		｡	｢	｣	､	･	ｦ	ｧ	ｨ	ｩ	ｪ	ｫ	ｬ	ｭ	ｮ	ｯ
B	ｰ	ｱ	ｲ	ｳ	ｴ	ｵ	ｶ	ｷ	ｸ	ｹ	ｺ	ｻ	ｼ	ｽ	ｾ	ｿ
C	ﾀ	ﾁ	ﾂ	ﾃ	ﾄ	ﾅ	ﾆ	ﾇ	ﾈ	ﾉ	ﾊ	ﾋ	ﾌ	ﾍ	ﾎ	ﾏ
D	ﾐ	ﾑ	ﾒ	ﾓ	ﾔ	ﾕ	ﾖ	ﾗ	ﾘ	ﾙ	ﾚ	ﾛ	ﾜ	ﾝ	ﾞ	ﾟ
E
F

Second byte
	0	1	2	3	4	5	6	7	8	9	A	B	C	D	E	F
0
1
2
3
4
5
6
7
8
9
A
B
C
D
E
F

	Non printable ASCII character
	Unaltered ASCII character
	Modified ASCII character
	Single-byte half-width katakana
	First byte of a double-byte JIS X 0208 character
	Unused as first byte of a JIS X 0208 character
	Second byte of a double-byte JIS X 0208 character whose first half of the JIS sequence was odd
	Second byte of a double-byte JIS X 0208 character whose first half of the JIS sequence was even
	Unused as second byte of a JIS X 0208 character