SICStus Prolog provides two execution modes: the iso mode, which
is fully compliant with the International Standard ISO/IEC 13211-1
(PROLOG: Part 1--General Core), and the sicstus mode, which
supports code written in earlier versions of SICStus Prolog. The
execution mode can be changed using the Prolog flag language;
see State Info. Note, however, that SICStus Prolog does not offer a
strictly conforming mode that rejects uses of implementation specific
features.
To aid programmers who wish to write standard compliant programs,
built-in predicates that are part of the ISO Prolog Standard are
annotated with [ISO] in this manual. If such a predicate
behaves differently in sicstus mode, an appropriate clarification
is given. For the few predicates that have a completely different
meaning in the two modes, two separate descriptions are given. The one
for the iso mode is annotated with [ISO only], while the
sicstus mode version is annotated with [SICStus only].