Utf 8 Character Set3/11/2021
The first two red cells ( C0 and C1 ) could be used only for a 2-byte encoding of a 7-bit ASCII character which should be encoded in 1 byte; as described below, such overlong sequences are disallowed. 37 To understand why this is, consider the character 128, hex 80, binary 1000 0000.Defined by the Unicode Standard, the name is derived from Unicode (or Universal Coded Character Set ) Transformation Format 8-bit.Code points with lower numerical values, which tend to occur more frequently, are encoded using fewer bytes.
Since ASCII bytes do not occur when encoding non-ASCII code points into UTF-8, UTF-8 is safe to use within most programming and document languages that interpret certain ASCII characters in a special way, such as ( slash ) in filenames, ( backslash ) in escape sequences, and in printf. Ken Thompson and Rob Pike produced the first implementation for the Plan 9 operating system in September 1992. This led to its adoption by XOpen as its specification for FSS-UTF, which would first be officially presented at USENIX in January 1993 and subsequently adopted by the Internet Engineering Task Force (IETF) in RFC 2277 ( BCP 18 ) for future Internet standards work, replacing Single Byte Character Sets such as Latin-1 in older RFCs. The ASCII -only figure includes all web pages that only contain ASCII characters, regardless of the declared header. Using non-UTF-8 encodings can have unexpected results. Many other standards only support UTF-8, e.g. JSON exchange requires it. GB 18030 (effectively nb 2 ) has a 12.0 share in China 13 14 and a 0.3 share world-wide. Big5 is another popular Chinese encoding with less than 0.1 share world-wide, but is popular in Hong Kong and more so in Taiwan where it has 5.6 share. The single-byte Windows-1251 is twice as efficient for the Cyrillic script and is used for 9.6 of Russian web sites. E.g. Greek and Hebrew encodings are also twice as efficient, but still those languages have well over 95 use of UTF-8. EUC-KR is more efficient for Korean text and is used for 11.5 of South Korean websites. Shift JIS and EUC-JP have a 8.7 share combined on Japanese websites (the more popular Shift JIS has 0.1 global share). With the exception of GB 18030 and UTF-16, these encodings were designed for specific languages, and do not support all Unicode characters. As of February 2021 update, the Breton language has the lowest UTF-8 use on the Web of any tracked language, with 87.5 use. Several languages have 100.0 use of UTF-8 on the web, such as Bengali, Punjabi, Tagalog, Lao, Marathi, Kannada, Kurdish, Pashto, Javanese, Greenlandic ( Kalaallisut ) and Iranian languages 21 22 and sign languages. Utf 8 Character Set Software To UseThis is primarily due to editors that will not display or write UTF-8 unless the first character in a file is a byte order mark, making it impossible for other software to use UTF-8 without being rewritten to ignore the byte order mark on input and add it on output. UTF-16 files are also fairly common on Windows, but not in other systems. This is due to a belief that direct indexing of code points is more important than 8-bit compatibility. International Components for Unicode (ICU) has historically used UTF-16, and still does only for Java; while for CC UTF-8 is now supported as the Default Charset 28 including the correct handling of illegal UTF-8. The Go programming languages uses UTF-8 for its source code, and its string primitive assumes UTF-8 encoding by default. Microsoft now recommends the use of UTF-8 for applications using the Windows API, while continuing to maintain a legacy Unicode (meaning UTF-16) interface. The next 1,920 characters need two bytes to encode, which covers the remainder of almost all Latin-script alphabets, and also Greek, Cyrillic, Coptic, Armenian, Hebrew, Arabic, Syriac, Thaana and NKo alphabets, as well as Combining Diacritical Marks. Three bytes are needed for characters in the rest of the Basic Multilingual Plane, which contains virtually all characters in common use, 32 including most Chinese, Japanese and Korean characters. Four bytes are needed for characters in the other planes of Unicode, which include less common CJK characters, various historic scripts, mathematical symbols, and emoji (pictographic symbols). The two leading zeros are added because a three-byte encoding needs exactly sixteen bits from the code point. So the next six bits of the code point are stored in the low order six bits of the next byte, and 10 is stored in the high order two bits to mark it as a continuation byte (so 10 00 0010 ). The colors indicate how bits from the code point are distributed among the UTF-8 bytes. Additional bits added by the UTF-8 encoding process are shown in black. The upper half ( 0 to 7 ) is for bytes used only in single-byte codes, so it looks like a normal code page; the lower half is for continuation bytes ( 8 to B ) and leading bytes ( C to F ), and is explained further in the legend below. This character never occurs as the first byte of a multi-byte sequence. The text shows the Unicode blocks encoded by sequences starting with this byte, and the hexadecimal code point shown in the cell is the lowest character value encoded using that leading byte. The first two red cells ( C0 and C1 ) could be used only for a 2-byte encoding of a 7-bit ASCII character which should be encoded in 1 byte; as described below, such overlong sequences are disallowed. To understand why this is, consider the character 128, hex 80, binary 1000 0000.
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