                         IMP Core Environment Standard

                        Section 13: Reserved Identifiers
           *** WILL BE SHIFTED OUT OF STANDARD AS OF NEXT EDITION ***

       In the fullness of time, this section will be removed from the "Core"
    standard to become a document in its own right.  Its purpose is to
    identify common "useful" procedures to implementers in terms of a
    definition and an identifier, so that if an implementer chooses to add
    such a facility to an implementation it will normally have the same
    identifier as on other implementations.  This allows programmers to
    avoid any "false friend" effect when coding outside the bounds of the
    Core standard proper.  An example of a possible problem area might be in
    moving from a system in which a WAIT procedure was available with
    parameter integer Millisecs to one where WAIT was defined to have
    parameter long real Seconds.

       Procedures defined in this section of the standard must never be
    predefined.  Instead, they must be introduced into the program by means
    of an implementation defined include or spec statement.  An
    implementation is free to implement these same functions with other
    identifiers, but must not implement these identifiers with alternate
    definitions.