The description of how LATEX<#499#><#499#> font attributes are turned into TEX<#500#><#500#>
fonts is usually kept in a font definition (|.fd|) file. The
|.fd| file for family <#502#>family<#502#> in encoding <#503#>encoding<#503#> is called
|;SPMlt;ENC;SPMgt;;SPMlt;family;SPMgt;.fd|, for example |OT1cmr.fd| for Computer Modern Roman
or |T1ptm.fd| for Adobe Times.
Whenever LATEX<#504#><#504#> encounters an encoding/family combination that it
does not know (e.g.~if the document designer says
|<#505#>ptm<#505#>|) then LATEX<#506#><#506#> attempts to load the
appropriate |.fd| file. ``Not known'' means: there was no
| | declaration issued for this encoding/family
combination.
The declarations in the |.fd| file are responsible for telling
LATEX<#507#><#507#> how to load fonts for that encoding/family combination. If
the |.fd| file could not be found, a warning is issued and font
substitutions are made.