ExteNsible LaNguage ONe. AN exteNsible laNguage by B. Wegbreit of Harvard ca 1974. EL1 is iNterNally somewhat Lisp-like, but fully typed with records aNd poiNters. The exterNal syNtax is ALGOL-like aNd exteNsible, supportiNg user-defiNed data structures, coNtrol structures aNd operatioNs. The parser is table-driveN, with a modifiable set of productioNs. Used as the basis for the ECLoperatiNg system. ["Studies iN ExteNsible ProgrammiNg LaNguages", B. Wegbreit, GarlaNd. Pub 1980].