Objective-C is an object-oriented language built as a thin layer on top of C. It was created by Brad Cox in the early 1980s, who added a message-passing object model inspired by Smalltalk to the C language. Cox laid out the language and its philosophy in his 1986 book “Object-Oriented Programming: An Evolutionary Approach,” published by Addison-Wesley and now archived on the Internet Archive.
Apple’s own documentation describes Objective-C as “a superset of the C programming language” that “provides object-oriented capabilities and a dynamic runtime.” It “inherits the syntax, primitive types, and flow control statements of C and adds syntax for defining classes and methods.” Because it is a strict superset of C, ordinary C code compiles and runs unchanged inside an Objective-C program.
The language found its lasting home through NeXT, the company Steve Jobs founded after leaving Apple. NeXT adopted Objective-C as the language of its NeXTSTEP operating system and frameworks. When Apple acquired NeXT in 1996, that technology became the foundation of Mac OS X, and Objective-C became, in Apple’s words, “the primary programming language you use when writing software for OS X and iOS.”
Objective-C kept that role for years, including through the launch of the iPhone and the rise of the App Store. It was eventually succeeded by Swift, introduced in 2014 as a safer and more modern alternative, though the two languages were designed to coexist so that large existing codebases could migrate gradually.