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; this file
should contain nothing else (see Section 5.2.
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).