Since one of the main aims of the new standard LATEX is to provide a highly portable document format, the number of configuration possibilities is strictly limited. An important consequence of this is that any document that relies on any extension package must declare this package within the document file; this helps to ensure that the document will work at a different site, where the LATEX system may be configured differently.
Local configuration options are, by convention, placed in `configuration files', which have extension |cfg|. This file lists the possibilities for configuration in the most recent release of LATEX.