Background
The Unicode standard does not specify or create the font (typeface), a collection of graphical shapes called glyphs, itself. Rather, it defines the abstract characters as a specific number (known as a codepoint) and also defines the required changes of shape depending on the context the glyph is used in (e.g., Combining characters, precomposed characters and letter-diacritic combinations). The choice of font, which governs how the abstract UCS characters are converted into a bitmap or vector output that can be viewed on a screen or printed, is left up to the user. If a font is chosen which does not contain a glyph for a codepoint used in the document, typically a question mark ("?"), a box, or some other Substitute character is displayed.
Computer fonts use various techniques to display characters or glyphs. A Bitmap font contains a grid of dots known as pixels forming an image of each glyph in each face and size. Outline fonts (also known as Vector fonts) use drawing instructions or mathematical formulæ to describe each glyph. Stroke fonts use a series of specified lines (for the glyph's border) and additional information to define the profile, or size and shape of the line in a specific face and size, which together describe the appearance of the glyph.
Many fonts have kerning pairs which implements better spacing in between the characters. Fonts also includes embedded special orthographic rules to output certain combinations of letterforms (an alternative symbols for the same letter) be combined into special ligature forms (mixed characters). Operating System or Web-Browser (aka, User Agent) or both, which uses a font to display text on the screen or print media, can be programmed to use those embedded rules, or use external script-shaping technologies (also known as Rendering Technology or Smartfont Engine), and they can also be programmed to use either a large unicode font, or use multiple different fonts for different characters or languages.
No single "Unicode font" includes all the characters defined in the present revision of ISO 10646 (Unicode) standard, as it is continually adding more & more languages and characters. As a result, font developers and foundries are also incorporating those new characters in newer version or revision of a font, and correcting their previous errors if there were any.
The UCS has over 1.1 million code points, but only the first 65,536 (the Plane 0: Basic Multilingual Plane, or BMP) had entered into common use before 2000. (See the Mapping of Unicode characters article for more information on other planes, including Plane 1: SMP, Plane 2: SIP, Plane 14: SSP, Plane 15 and 16: reserved for PUA.)
The first Unicode fonts (with very large character set, and supporting many Unicode blocks) were Lucida Sans Unicode (released March 1993), Unihan font (1993), and Everson Mono (1995).
Read more about this topic: Unicode Typefaces
Famous quotes containing the word background:
“I had many problems in my conduct of the office being contrasted with President Kennedy’s conduct in the office, with my manner of dealing with things and his manner, with my accent and his accent, with my background and his background. He was a great public hero, and anything I did that someone didn’t approve of, they would always feel that President Kennedy wouldn’t have done that.”
—Lyndon Baines Johnson (1908–1973)
“Pilate with his question “What is truth?” is gladly trotted out these days as an advocate of Christ, so as to arouse the suspicion that everything known and knowable is an illusion and to erect the cross upon that gruesome background of the impossibility of knowledge.”
—Friedrich Nietzsche (1844–1900)
“Silence is the universal refuge, the sequel to all dull discourses and all foolish acts, a balm to our every chagrin, as welcome after satiety as after disappointment; that background which the painter may not daub, be he master or bungler, and which, however awkward a figure we may have made in the foreground, remains ever our inviolable asylum, where no indignity can assail, no personality can disturb us.”
—Henry David Thoreau (1817–1862)