From Cibernética Americana

At the time of our initial working exposure, Burroughs had distinct architectures/divisions, Large Systems (B 6 and 7000 then A series) and Medium Systems (B 17 and 1900, then B series?).

Here, by LargeSystem we mean the conceptual VM implemented by the current DMS III core domain control program.

Each host participating in the DCP is considered to be a processor under control of the PVM and it's file system and IO capabilities are modelled using an amalgam of the Large Systems library and Algol68 transput definitions where a library is simply a collection of Books as defined in the Revised Report.