Unix is a family of operating systems developed in the 1970s at Bell Labs by Ken Thompson, Dennis Ritchie, and others. Known for its modular design and command-line interface, it profoundly influenced software development and the architecture of modern computer systems.
Initially written largely in assembly language, it was famously rewritten in the C programming language in the early 1970s, making it highly portable across different hardware platforms. Key design principles include a hierarchical file system, treating everything as a file, and a "toolkit philosophy" where small, simple utilities can be combined using pipes and redirection.
Its influence is pervasive, inspiring the development of many other operating systems like Linux and macOS, and leading to the POSIX standard, which defines a set of application programming interfaces (APIs) for software compatibility across Unix-like systems.