The main difference between LaTeX~2.09 and LaTeX2e<#79#><#79#> is in the
commands before 7.
In LaTeX~2.09, documents had <#80#>styles<#80#>,
such as <#81#>article<#81#> or <#82#>book<#82#>, and <#83#>options<#83#>,
such as <#84#>twoside<#84#> or <#85#>epsfig<#85#>.
These were indicated by the 8 command:
9[<<#87#>options<#87#>>]{<<#88#>style<#88#>>}
For example, to specify a two-sided article with encapsulated
PostScript figures, you said:
verbatim2
However, there were two different types of document style option:
<#90#>built-in options<#90#> such as 10; and <#91#>packages<#91#> such as
11. These were very different, since any LaTeX<#92#><#92#> document
style could use the <#93#>epsfig<#93#> package but only document styles
which declared the <#94#>twoside<#94#> option could use that option.
To avoid this confusion, LaTeX2e<#95#><#95#> differentiates between built-in
options and packages. These are given by the new 12 and
13 commands:
14[<<#97#>options<#97#>>]{<<#98#>class<#98#>>}
15[<<#99#>options<#99#>>]{<<#100#>packages<#100#>>}
For example, to specify a two-sided article with encapsulated
PostScript figures, you now write:
verbatim3
You can load more than one package with a single 16
command; for example, rather than writing:
verbatim4
you can specify:
verbatim5
Note that LaTeX2e<#102#><#102#> still understands the LaTeX~2.09 17
command. This command causes LaTeX2e<#103#><#103#> to enter <#104#>LaTeX~2.09
compatibility mode<#104#>, which is described in Section~#Sec209#105>.
You should not, however, use the 18 command for new
documents because this compatibility mode is very slow and the new
features of LaTeX2e<#106#><#106#> are not available in this mode.
To help differentiate between classes and packages, document classes
now end with 19 rather than 20. Packages still end with
21, since most LaTeX~2.09 packages work well with LaTeX2e.