= OpenType
{c}
<OpenType> is a table-based <computer font> format separating <glyph> representations, character mapping, measurements, naming metadata and optional layout rules. Its `cmap` table selects default <glyph indices> for encoded <text characters>; substitution and positioning tables support more elaborate <text shaping>.
An <OpenType> <computer font> can contain <TrueType> outlines or Compact Font Format outlines, and the specification also provides for bitmap and other <glyph> representations. The file format therefore does not prescribe a single kind of outline geometry. Extensions such as `.ttf` and `.otf` are useful conventions, but the actual table contents determine the available representation.<The OpenType Font File by Microsoft>[Font file; Font tables; TrueType outlines; PostScript outlines; tables related to bitmap glyphs]{ref}
This organization lets one system answer separate questions: which <glyph> represents this text, how much space should it occupy, and how should it be drawn at this size? A language's contextual forms can change the first answer without changing the original <Unicode> text.
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