Expanding upon the capabilities of TrueType, OpenType provides better support for international character sets, protection for font data, and advanced typographic control. OpenType fonts allow a rich mapping between characters and glyphs, thus enabling support for ligatures, positional forms, alternates, and other substitutions. Another benefit of OpenType fonts is their layout tables for multilingual text, which give font designers greater typographic control. They are also portable across platforms and can support all common encoding systems.
OpenType fonts for complex scripts use Windows operating-system services such as Uniscribe to shape and position glyph strings that character strings are mapped to. Uniscribe, in turn, uses the OpenType Layout services library, which is a set of helper functions to lay out the glyph string during text processing.
To take full advantage of OpenType fonts, pay attention to the order of lookups. When you construct lookups, try to use a format that will yield the greatest storage efficiency. In general, be current on guidelines for creating Open-Type fonts-including recommendations on usage of OpenType features, byte ordering, outline formats, file names, as well as table alignment and length.