In Unicode 3.2, this usage is deprecated in favor of the " Word Joiner" character, U+2060. If the BOM character appears in the middle of a data stream, Unicode says it should be interpreted as a " zero-width non-breaking space" (inhibits line-breaking between word-glyphs). This use of the BOM character is called a "Unicode signature". Therefore, placing an encoded BOM at the start of a text stream can indicate that the text is Unicode and identify the encoding scheme used. The byte sequence of the BOM differs per Unicode encoding (including ones outside the Unicode standard such as UTF-7, see table below), and none of the sequences is likely to appear at the start of text streams stored in other encodings.
Generally the receiving computer will swap the bytes to its own endianness, if necessary, and would no longer need the BOM for processing.
Hence, the process accessing the text can examine these first few bytes to determine the endianness, without requiring some contract or metadata outside of the text stream itself.
#Pgp zero byte file code#
The BOM is encoded in the same scheme as the rest of the document and becomes a noncharacter Unicode code point if its bytes are swapped. For the 16- and 32-bit representations, a computer receiving text from arbitrary sources needs to know which byte order the integers are encoded in. Unicode can be encoded in units of 8-bit, 16-bit, or 32-bit integers.
#Pgp zero byte file software#
Its presence interferes with the use of UTF-8 by software that does not expect non-ASCII bytes at the start of a file but that could otherwise handle the text stream.
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