potential patent infringements in FreeType 1 because parts of the TrueType hinting virtual machine were patented by Apple, a fact not mentioned in the TrueType standards. (Patent holders who contribute to standards published by a major standards body such as ISO are required to disclose the scope of their patents, but TrueType was not such a standard.) FreeType 2 included an optional automatic hinter to avoid the patented technology, but these patents have now expired so FreeType 2.4 now enables these features by default. Outlines The outlines of the characters (or glyphs) in TrueType fonts are made of straight line segments and quadratic Bézier curves. These curves are mathematically simpler and faster to process than cubic Bézier curves, which are used both in the PostScript-centered world of graphic design and in Type 1 fonts. However, most shapes require more points to describe with quadratic curves than cubics. This difference also means that it is not possible to convert Type 1 losslessly to the TrueType format, although in practice it is often possible to do a lossless conversion from TrueType to Type 1. Hinting language TrueType systems include a virtual machine that executes programs inside the font, processing the "hints" of the glyphs, in TrueType called “instructions”. These distort the control points which define the outline, with the intention that the rasterizer produce fewer undesirable features on the glyph. Each glyph's instruction set takes account of the size (in pixels) at which the glyph is to be displayed, as well as other less important factors of the display environment. Although incapable of receiving input and producing output as normally understood in programming, the TrueType instruction language does offer the other prerequisites of programming languages: conditional branching (IF statements), looping an arbitrary number of times (FOR- and WHILE-type statements), variables (although these are simply numbered slots in an area of memory reserved by the font), and encapsulation of code into functions. Special instructions called delta instructions are the lowest level control, moving a control point at just one pixel size. The hallmark of effective TrueType glyph programming techniques is that it does as much as possible using variables defined just once in the whole font (e.g., stem widths, cap height, x-height). This means avoiding delta instructions as much as possible. This helps the font developer to make major changes (e.g., the point at which the entire font's main stems jump from 1