The byte order mark (BOM) is a Unicode character used to signal the endianness (byte order) of a text file or stream. It is encoded at U+FEFF byte order mark (BOM). BOM use is optional, and, if used, should appear at the start of the text stream. Beyond its specific use as a byte-order indicator, the BOM character may also indicate which of the several Unicode representations the text is encoded in.
Because Unicode can be encoded as 16-bit or 32-bit integers, a computer receiving these encodings from arbitrary sources needs to know which byte order the integers are encoded in. The BOM gives the producer of the text a way to describe the text stream's endianness to the consumer of the text without requiring some contract or metadata outside of the text stream itself. Once the receiving computer has consumed the text stream, it presumably processes the characters in its own native byte order and no longer needs the BOM. Hence the need for a BOM arises in the context of text interchange, rather than in normal text processing within a closed environment.
Read more about Byte Order Mark: Usage, Representations of Byte Order Marks By Encoding
Famous quotes containing the words order and/or mark:
“It seems only yesterday that we saw
The movie with the cows in it
And turned to one at your side, who burped
As morning saw a new garnet-and-pea-green order propose
Itself out of the endless bathos, like science-fiction lumps.”
—John Ashbery (b. 1927)
“Commerce has set the mark of selfishness,
The signet of its all-enslaving power,
Upon a shining ore, and called it gold:
Before whose image bow the vulgar great,
The vainly rich, the miserable proud,
The mob of peasants, nobles, priests, and kings,
And with blind feelings reverence the power
That grinds them to the dust of misery.”
—Percy Bysshe Shelley (1792–1822)