FoCus is a wrapper around the standard FORMAT utility. It allows you to customize the FORMAT DSL by adding new directive characters or modifying the standard ones. The semantics of these directive characters is specified in a so-called "format table", a concept very close to that of readtables. FoCus ultimately translates into regular FORMAT calls.
FoCus's homepage contains a lot of resources, including online documentation in various formats.
- Didier Verna