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:
“However fiercely opposed one may be to the present order, an old respect for the idea of order itself often prevents people from distinguishing between order and those who stand for order, and leads them in practise to respect individuals under the pretext of respecting order itself.”
—Antonin Artaud (1896–1948)
“So unrecorded did it slip away,
So blind was I to see and to foresee,
So dull to mark the budding of my tree
That would not blossom yet for many a May.
If only I could recollect it, such
A day of days! I let it come and go
As traceless as a thaw of bygone snow;
It seemed to mean so little, meant so much;
If only now I could recall that touch,
First touch of hand in hand—Did one but know!”
—Christina Georgina Rossetti (1830–1894)