|. In LATEX~2.09, documents had styles, such as |article| or |book|, and options, such as |twoside| or |epsfig|. These were indicated by the | command:
|<#80#>options<#80#><#81#>style<#81#>
For example, to specify a two-sided article with encapsulated PostScript figures, you said: 
verbatim35#
However, there were two different types of document style option: built-in options such as |twoside|; and packages such as |epsfig.sty|. These were very different, since any LATEX<#87#><#87#> document style could use the |epsfig| package but only document styles which declared the |twoside| option could use it. To avoid this confusion, LATEX2e<#88#><#88#> differentiates between built-in options and packages. These are given by the new | and | commands:
|<#90#>options<#90#><#91#>class<#91#>
|<#92#>options<#92#><#93#>packages<#93#>
For example, to specify a two-sided article with encapsulated PostScript figures, you now write: 
verbatim36#
You can load more than one package with a single | command; for example, rather than writing: 
verbatim37#
you can specify: 
verbatim38#
Note that LATEX2e<#101#><#101#> still understands the LATEX~2.09 | command. This command causes LATEX2e<#102#><#102#> to enter LATEX~2.09 compatibility mode, which is described in Section~#Sec:209#104>. You should not, however, use the | command for new documents because this compatibility mode is very slow and the new features of LATEX2e<#105#><#105#> are not available in this mode. To help differentiate between classes and packages, document classes now end with |.cls| rather than |.sty|. Packages still end with |.sty|, since most LATEX~2.09 packages work well with LATEX2e.