The first commercial object-oriented version of the C programming language. Objective C is mostly used to write Mac OS X and GNUstep applications, which are created in the OpenStep development environment. Applications use the Mac's Cocoa object library or the GNUstep library, which is part of many Linux distributions. Windows versions are also available, and numerous hardware platforms are supported under the GNU gcc compiler.

A superset of the C language, most C programs can be compiled with an Objective C compiler. Objective C requires a runtime module that is considerably more lightweight than virtual machines used by languages such as Java. Originally developed by the Stepstone Corporation, it was licensed by NeXT Computer (later acquired by Apple) and made part of NeXT's OpenStep. See OpenStep, GNUstep and object-oriented programming.