To switch to another <#167#>family<#167#> one may use 17,
18 or 19 denoting the `cmroman', `cmsansserif' or
`cmtypewriter' <#168#>family<#168#>, respectively. The new font is selected
without changing the current <#169#>series<#169#>, <#170#>shape<#170#>, and <#171#> size<#171#>. E.g., if the current font is <#172#>cmbx10<#172#> (that is <#173#> family<#173#> `computer modern roman', <#174#>series<#174#> `bold extended',
<#175#>shape<#175#> `normal', and <#176#>size<#176#> `10pt') then 20 will
change to <#177#>cmssbx10<#177#> (that is <#178#>family<#178#> `computer modern
sansserif', <#179#>series<#179#> `bold extended', <#180#>shape<#180#> `normal', and
<#181#>size<#181#> `10pt'). Using, e.g., 21 afterward will
produce a warning and switch to <#182#>cmtt10<#182#> because the `computer
modern typewriter' <#183#>family<#183#> does not contain a `bold extended'
<#184#>series<#184#>; therefore the default (`medium') <#185#>series<#185#> is tried.