Objective-C is an object-oriented programming language that is a direct descendant of the C programming language. It was created in the early 1980s by Brad Cox and Tom Love, and it was designed to add object-oriented capabilities to the C language while maintaining full compatibility with it. Objective-C was the primary programming language used for developing software for the Apple operating systems macOS and iOS, until it was largely superseded by Swift, another language developed by Apple. One of the distinctive features of Objective-C is its use of a dynamic runtime, which allows for features such as dynamic typing and dynamic binding. This means that objects can be created and modified at runtime, providing a high level of flexibility and dynamism in the language. Objective-C syntax is notable for its use of message passing instead of traditional function calls. When an object receives a message, it determines at runtime which method to invoke to handle that message. This dynamic messaging system is a key aspect of the language's object-oriented design and is facilitated by the language's runtime system. The language includes features such as categories, which allow for the extension of existing classes without the need for subclassing, and protocols, which are similar to interfaces in other programming languages and define a set of methods that any class can implement. Objective-C was the foundation of the Cocoa and Cocoa Touch frameworks, which are essential for developing native macOS and iOS applications, respectively. These frameworks provide a rich set of APIs for user interface design, networking, file handling, and much more. Despite the rise of Swift, Objective-C remains an important language for maintaining and updating the vast number of existing applications that were written in it. It also serves as a bridge for developers transitioning to Swift, as the two languages can be used interoperably within the same project. Objective-C's influence can be seen in the design of Swift, which incorporates many of the language's object-oriented concepts while introducing modern features and a cleaner syntax. However, as Swift continues to evolve and gain popularity, Objective-C's role in new development projects has diminished, although it remains a significant part of the Apple development ecosystem due to the legacy codebase written in the language.