to 2 pixels wide) most of the way through development. Creating a very well-instructed TrueType font remains a significant amount of work, despite the increased user-friendliness of programs for adding instructions to fonts. Many TrueType fonts therefore have only rudimentary instructions, or have them automatically applied by the font editor, with results of various quality. Embedding protection The TrueType format allows for the most basic type of digital rights management – an embeddable flag field that specifies whether the author allows embedding of the font file into things like PDF files and websites. Anyone with access to the font file can directly modify this field, and simple tools exist to facilitate modifying it (obviously, modifying this field does not modify the font license and does not give extra legal rights). These tools have been the subject of controversy over potential copyright issues. Emoji Apple has implemented a proprietary extension to allow color .ttf files for its emoji font Apple Color Emoji. File formats Basic A basic font is composed of multiple tables specified in its header. A table name can have up to 4 letters. A .ttf extension indicates a regular TrueType font or an OpenType font with TrueType outlines. Windows end user defined character editor (EUDCEDIT.EXE) creates TrueType font with name EUDC.TTE. An OpenType font with PostScript outlines must have an .otf extension. In principle an OpenType font with TrueType outlines may have an .otf extension, but this has rarely been done in practice. In classic Mac OS and macOS, OpenType is one of several formats referred to as data-fork fonts, as they lack the classic Mac resource fork. Collection TrueType Collection (TTC) is an extension of TrueType format that allows combining multiple fonts into a single file, creating substantial space savings for a collection of fonts with many glyphs in common. They were first available in Chinese, Japanese, and Korean versions of Windows, and supported for all regions in Windows 2000 and later. Classic Mac OS included support of TTC starting with Mac OS 8.5. A TrueType Collection file begins with a ttcf table that allows access to the fonts within the collection by pointing to individual headers for each included font. The fonts within a collection share the same glyph-outline table, though each font can refer to subsets within those outlines in its own manner, through its cmap, name and loca tables. Collection files bear a .ttc