As mentioned before, primitive font selection commands like
\fontfamily, \fontseries, \fontshape,
\fontsize, and
\selectfont are also available to carry out the change.
E.g.,
\fontshape{n}\fontfamily{cmss}\selectfont
will
switch to the `cmsansserif' family with `normal' shape.4 This article was set in concrete roman type
by simply writing \fontfamily{ccr}\selectfont
following the \begin{document}
command.5 Of course, the
\documentstyle command also specifies a style option (` concrete') which sets up the internal tables for these fonts.