<\body> In this section, we describe the environment variables which control the rendering of fonts. Font properties may be controlled globally for the whole document in and locally for document fragments in . From an abstract point of view, a is defined to be a graphically consistent way of rendering strings. Fonts are usually made up from glyphs like ``x'', ``ffi'', ``>'', ``>>'', When rendering a string, the string is decomposed into glyphs so as to take into account ligatures (like fi, fl, ff, ffi, ffl). Next, the individual glyphs are positioned while taking into account kerning information (in ``xo'' the ``o'' character is slightly shifted to the left so as to take profit out of the hole in the ``x''). In the case of mathematical fonts, also provides a coherent rendering for resizable characters, like the large brackets in <\equation*> >>|)>>>>|)>. Similarly, a is a family of fonts with different characteristics (like font weight, slant, ), but with a globally consistent rendering. One also says that the fonts in a font family ``mix well together''. For instance, the standard computer modern roman font and its and variants mix well together, but the computer modern roman font and the font do not. <\remark> In versions of prior to 1.99.1, the fonts for the mathematical and programming modes could be controlled independently using the environment variables , , , , , , , . In more recent versions of , the environment variables , , and directly control the font for all modes. <\explain> <|explain> These variables control the main name of the font, also called the . For instance: <\tm-fragment> , , , Similarly, supports various mathematical fonts: <\tm-fragment> Roman: +b=c> Adobe: +b=c>> New roman: +b=c>> Concrete: +b=c>> Most fonts only implement a subset of all Unicode glyphs. Sometimes, the user might wish to combine several fonts to cover a larger subset. For instance, when specifying or as the name, ordinary text and mathematics will be typeset using the default font, whereas Chinese text will use the font. Similarly, when specifying as the name, ordinary text will be typeset using the default font, but mathematical formulas using the font. <\explain> <|explain> This variable selects a variant of the major font, like a sans serif font, a typewriter font, and so on. As explained above, variants of a given font are designed to mix well together. Physically speaking, many fonts do not come with all possible variants (sans serif, typewriter, ), in which case tries to fall back on a suitable alternative font. Typical variants for text fonts are (roman), (typewriter) and (sans serif): <\tm-fragment> roman, and Sans serif formula: =sin x*cos y+cos x*sin y>> <\explain> <|explain> The font series determines the weight of the font. Most fonts only provide and font weights. Some fonts also provide as a possible value. <\tm-fragment> medium, <\explain> <|explain> The font shape determines other characters of a font, like its slant, whether we use small capitals, whether it is condensed, and so on. For instance, <\tm-fragment> , , , , , >, >, >, <\explain> <|explain> The base font size is specified in units|../basics/lengths.en.tm> and is usually invariant throughout the document. Usually, the base font size is , , or . Other font sizes are usually obtained by changing the |env-general.en.tm#magnification> or the relative . <\tm-fragment> , , , <\explain> <|explain> The real font size is obtained by multiplying the by the multiplier. The following standard font sizes are available from : |||||>|>||>|>|>||>|>|>||>|>|>||>|>>>>|Standard font sizes.> From a mathematical point of view, the multipliers are in a geometric progression with factor >. Notice that the font size is also affected by the . <\explain> <|explain> The rendering quality of raster fonts (also called Type 3 fonts), such as the fonts generated by the program is controlled through its discretization precision in dots per inch. Nowadays, most laser printers offer a printing quality of at least , which is also the default setting for . For really high quality printing, professionals usually use a precision of . The is usually set once and for all for the whole document.