Object-Oriented Programming and the Objective-C Language.
Objective-C syntax is a superset of standard C syntax, and its compiler works for both C and Objective-C source code. The compiler recognizes Objective-C source files by a .m extension, just as it recognizes files containing only standard C syntax by a .c extension. The Objective-C language is fully compatible with ANSI standard C.
www.toodarkpark.org/computers/objc/   reviews

Object Oriented Programming in Objective-C.
These documents provide a brief introduction to Object Oriented Programming in the Objective-C language. The first two documents were developed from class notes written by Gerrit Huizenga for the course Introduction to Objective-C on the NeXT Machine at Purdue University.
www.cs.indiana.edu/classes/c304/oop-intro.html   reviews