Search results
Results from the WOW.Com Content Network
A UTF-8 file that contains only ASCII characters is identical to an ASCII file. Legacy programs can generally handle UTF-8 encoded files, even if they contain non-ASCII characters. For instance, the C printf function can print a UTF-8 string because it only looks for the ASCII '%' character to define a formatting string. All other bytes are ...
UTF-7 (7-bit Unicode Transformation Format) is an obsolete variable-length character encoding for representing Unicode text using a stream of ASCII characters. It was originally intended to provide a means of encoding Unicode text for use in Internet E-mail messages that was more efficient than the combination of UTF-8 with quoted-printable.
It was designed for backward compatibility with ASCII: the first 128 characters of Unicode, which correspond one-to-one with ASCII, are encoded using a single byte with the same binary value as ASCII, so that a UTF-8-encoded file using only those characters is identical to an ASCII file.
The same character converted to UTF-8 becomes the byte sequence EF BB BF. The Unicode Standard allows the BOM "can serve as a signature for UTF-8 encoded text where the character set is unmarked". [74] Some software developers have adopted it for other encodings, including UTF-8, in an attempt to distinguish UTF-8 from local 8-bit code pages.
ISO-8859-1, Windows-1252, and the original 7-bit ASCII were the most common character encoding methods on the World Wide Web until 2008, when UTF-8 overtook them. [57] ISO/IEC 4873 introduced 32 additional control codes defined in the 80–9F hexadecimal range, as part of extending the 7-bit ASCII encoding to become an 8-bit system. [63]
The Universal Coded Character Set (UCS, Unicode) is a standard set of characters defined by the international standard ISO/IEC 10646, Information technology — Universal Coded Character Set (UCS) (plus amendments to that standard), which is the basis of many character encodings, improving as characters from previously unrepresented typing systems are added.
[6] [7] [8] The Encoding Standard further stipulates that new formats, new protocols (even when existing formats are used) and authors of new documents are required to use UTF-8 exclusively. [9] Besides UTF-8, the following encodings are explicitly listed in the HTML standard itself, with reference to the Encoding Standard: [8]
Although not strictly required, UTF-8 is usually also transfer encoded to avoid problems across seven-bit mail servers. MIME transfer encoding of UTF-8 makes it either unreadable as a plain text (in the case of base64) or, for some languages and types of text, heavily size inefficient (in the case of quoted-printable).