Unix

Unix is a family of multitasking, multiuser operating systems that originated at Bell Labs in the late 1960s. Developed by Ken Thompson, Dennis Ritchie, and others, Unix was designed to be portable and to support collaboration and research. A pivotal decision was to reimplement core utilities and the kernel in the C programming language, which facilitated portability to different hardware.

Unix systems generally provide a hierarchical file system, a command-line shell, standard programming interfaces, and processes with interprocess communication. The Unix philosophy emphasizes small, interoperable tools that do one thing well and can be combined via pipes and text streams. Networking, device drivers, and security models are integrated in the kernel and system utilities.

Major Unix flavors emerged in the 1980s and 1990s, including System V and BSD variants. The Open Group now maintains the Unix trademark and certifies systems to the Single UNIX Specification; many modern operating systems—such as macOS, Solaris, AIX, and HP-UX—are Unix or Unix-like. Linux, while feature-compatible with Unix, is generally described as Unix-like rather than Unix proper.

Unix has had a lasting impact on software development and operating system design. Its concepts, including hierarchical file systems, shells, pipes, and portability via C, influenced countless successors and form the basis for most contemporary servers, embedded systems, and desktop environments.