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<title>Using Fonts (The GNU Troff Manual)</title>
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Next: <a href="Manipulating-Type-Size-and-Vertical-Spacing.html" accesskey="n" rel="next">Manipulating Type Size and Vertical Spacing</a>, Previous: <a href="Page-Control.html" accesskey="p" rel="prev">Page Control</a>, Up: <a href="GNU-troff-Reference.html" accesskey="u" rel="up">GNU <code class="code">troff</code> Reference</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Request-Index.html" title="Index" rel="index">Index</a>]</p>
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<h3 class="section" id="Using-Fonts-1">5.19 Using Fonts</h3>
<a class="index-entry-id" id="index-font"></a>
<a class="index-entry-id" id="index-typeface"></a>
<a class="index-entry-id" id="index-font-family"></a>
<a class="index-entry-id" id="index-font-style"></a>
<a class="index-entry-id" id="index-style_002c-font"></a>
<a class="index-entry-id" id="index-family_002c-font"></a>
<a class="index-entry-id" id="index-text-font"></a>
<a class="index-entry-id" id="index-special-font"></a>
<a class="index-entry-id" id="index-unstyled-font"></a>
<a class="index-entry-id" id="index-font_002c-text"></a>
<a class="index-entry-id" id="index-font_002c-special"></a>
<a class="index-entry-id" id="index-font_002c-unstyled"></a>
<p>In digital typography, a <em class="dfn">font</em> is a collection of characters in a
specific typeface that a device can render as glyphs at a desired
size.<a class="footnote" id="DOCF72" href="groff.html_fot.html#FOOT72"><sup>72</sup></a> A <code class="code">roff</code> formatter can change typefaces at any
point in the text. The basic faces are a set of <em class="dfn">styles</em> combining
upright and slanted shapes with normal and heavy stroke weights:
‘<samp class="samp">R</samp>’, ‘<samp class="samp">I</samp>’, ‘<samp class="samp">B</samp>’, and ‘<samp class="samp">BI</samp>’—these stand for
<i class="slanted">roman</i>, <i class="slanted">italic</i>, <i class="slanted">bold</i>, and
<i class="slanted">bold-italic</i>. For linguistic text, GNU <code class="code">troff</code> groups
typefaces into <em class="dfn">families</em> containing each of these
styles.<a class="footnote" id="DOCF73" href="groff.html_fot.html#FOOT73"><sup>73</sup></a> A <em class="dfn">text font</em> is thus often a family
combined with a style, but it need not be: consider the <code class="code">ps</code> and
<code class="code">pdf</code> devices’ <code class="code">ZCMI</code> (Zapf Chancery Medium italic)—often,
no other style of Zapf Chancery Medium is provided. On typesetting
devices, at least one <em class="dfn">special font</em> is available, comprising
<em class="dfn">unstyled</em> glyphs for mathematical operators and other purposes.
</p>
<a class="index-entry-id" id="index-font-description-file"></a>
<a class="index-entry-id" id="index-description-file_002c-font"></a>
<a class="index-entry-id" id="index-file_002c-font-description"></a>
<a class="index-entry-id" id="index-font-metrics"></a>
<a class="index-entry-id" id="index-metrics_002c-font"></a>
<a class="index-entry-id" id="index-mounting-position"></a>
<a class="index-entry-id" id="index-mounting-position-1"></a>
<a class="index-entry-id" id="index-position_002c-mounting"></a>
<p>Like <abbr class="acronym">AT&T</abbr> <code class="code">troff</code>, GNU <code class="code">troff</code> does not itself load
or manipulate a digital font file;<a class="footnote" id="DOCF74" href="groff.html_fot.html#FOOT74"><sup>74</sup></a> instead it
works with a <em class="dfn">font description file</em> that characterizes it,
including its glyph repertoire and the <em class="dfn">metrics</em> (dimensions) of
each glyph.<a class="footnote" id="DOCF75" href="groff.html_fot.html#FOOT75"><sup>75</sup></a> This
information permits the formatter to accurately place glyphs with
respect to each other. Before using a font description, the formatter
associates it with a <em class="dfn">mounting position</em>, a place in an ordered list
of available typefaces.
<a class="index-entry-id" id="index-abstract-font-style"></a>
<a class="index-entry-id" id="index-font-style_002c-abstract"></a>
<a class="index-entry-id" id="index-style_002c-font_002c-abstract"></a>
So that a document need not be strongly coupled to a specific font
family, in GNU <code class="code">troff</code> an output device can associate a style in
the abstract sense with a mounting position. Thus the default family
can be combined with a style dynamically, producing a <em class="dfn">resolved font
name</em>.
</p>
<p>Fonts often have trademarked names, and even Free Software fonts can
require renaming upon modification. <code class="code">groff</code> maintains a
convention that a device’s serif font family is given the name ‘<samp class="samp">T</samp>’
(“Times”), its sans-serif family ‘<samp class="samp">H</samp>’ (“Helvetica”), and its
monospaced family ‘<samp class="samp">C</samp>’ (“Courier”). Historical inertia has driven
<code class="code">groff</code>’s font identifiers to short uppercase abbreviations of font
names, as with ‘<samp class="samp">TR</samp>’, ‘<samp class="samp">TI</samp>’, ‘<samp class="samp">TB</samp>’, ‘<samp class="samp">TBI</samp>’, and a
special font ‘<samp class="samp">S</samp>’.
</p>
<p>The default family used with abstract styles can be changed at any time;
initially, it is ‘<samp class="samp">T</samp>’. Typically, abstract styles are arranged in
the first four mounting positions in the order shown above. The default
mounting position, and therefore style, is always ‘<samp class="samp">1</samp>’ (‘<samp class="samp">R</samp>’).
By issuing appropriate formatter instructions, you can override these
defaults before your document writes its first glyph.
</p>
<a class="index-entry-id" id="index-graphic-renditions"></a>
<a class="index-entry-id" id="index-renditions_002c-graphic"></a>
<a class="index-entry-id" id="index-character-cell-attributes"></a>
<a class="index-entry-id" id="index-attributes_002c-character-cell"></a>
<a class="index-entry-id" id="index-cell_002c-character_002c-attributes"></a>
<p>Terminal output devices cannot change font families and lack special
fonts. They support style changes by overstriking, or by altering
ISO 6429/ECMA-48 <em class="dfn">graphic renditions</em> (character cell
attributes).
</p>
<ul class="mini-toc">
<li><a href="Selecting-Fonts.html" accesskey="1">Selecting Fonts</a></li>
<li><a href="Font-Families.html" accesskey="2">Font Families</a></li>
<li><a href="Font-Positions.html" accesskey="3">Font Positions</a></li>
<li><a href="Using-Symbols.html" accesskey="4">Using Symbols</a></li>
<li><a href="Character-Classes.html" accesskey="5">Character Classes</a></li>
<li><a href="Special-Fonts.html" accesskey="6">Special Fonts</a></li>
<li><a href="Artificial-Fonts.html" accesskey="7">Artificial Fonts</a></li>
<li><a href="Ligatures-and-Kerning.html" accesskey="8">Ligatures and Kerning</a></li>
<li><a href="Italic-Corrections.html" accesskey="9">Italic Corrections</a></li>
<li><a href="Dummy-Characters.html">Dummy Characters</a></li>
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