Users can select new font encodings using the fontenc package. The
fontenc package has options for encodings; the last option becomes
the default encoding. For example, to use the OT2 (Washington
University Cyrillic encoding) and T1 encodings, with T1 as the
default, an author types:
\usepackage[OT2,T1]{fontenc}
For each font encoding <ENC> given as an option, this package loads
the encoding definition (<enc>enc.def, with an all
lower-case name) file; it also sets \encodingdefault to be the last
encoding in the option list.
The declarations in the encoding definition file <enc>enc.def for
encoding <ENC> are responsible for declaring this encoding and
telling LaTeX how to produce characters in this encoding.
The standard LaTeX format declares the OT1 and T1 text
encodings by inputting the files ot1enc.def and t1enc.def; it also
sets up various defaults which require that OT1-encoded fonts are
available.
Other encoding set-ups might be added to the distribution at a
later stage.
Thus the example above loads the files ot2enc.def and t1enc.def
and sets \encodingdefault to T1.
Warning: If you wish to use T1-encoded fonts other than the `cmr'
family then you may need to load the package (e.g. times)
that selects the fonts before loading fontenc (this
prevents the system from attempting to load any T1-encoded fonts from
the `cmr' family).