The Free On-line Dictionary of Computing (30 December 2018):

Objective C

    An object-oriented superset of ANSI C by Brad
   Cox, Productivity Products.  Its additions to C are few and
   are mostly based on Smalltalk.  Objective C is implemented
   as a preprocessor for C.  Its syntax is a superset of
   standard C syntax, and its compiler accepts both C and
   Objective C source code (filename extension ".m").

   It has no operator overloading, multiple inheritance, or
   class variables.  It does have dynamic binding.  It is
   used as the system programming language on the NeXT.  As
   implemented for NEXTSTEP, the Objective C language is fully
   compatible with ANSI C.

   Objective C can also be used as an extension to C++, which
   lacks some of the possibilities for object-oriented design
   that dynamic typing and dynamic binding bring to Objective
   C.  C++ also has features not found in Objective C.

   Versions exist for MS-DOS, Macintosh, VAX/VMS and
   Unix workstations.  Language versions by Stepstone,
   NeXT and GNU are slightly different.

   There is a library of (GNU) Objective C objects by
   R. Andrew McCallum  with similar
   functionality to Smalltalk's Collection objects.  It
   includes: Set, Bag, Array, LinkedList, LinkList,
   CircularArray, Queue, Stack, Heap, SortedArray,
   MappedCollector, GapArray and DelegateList.  Version: Alpha
   Release.  (ftp://iesd.auc.dk/pub/ObjC/).

   See also: Objectionable-C.

   ["Object-Oriented Programming: An Evolutionary Approach", Brad
   Cox, A-W 1986].

   (1999-07-10)