System V Release 4 (SVR4)

System V Release 4 (SVR4) is an operating system released in 1989 that combines features from previous UNIX systems, including System V and BSD (Berkeley Software Distribution). It was designed to enhance compatibility and performance, making it easier for software developers to create programs that run on different UNIX systems. SVR4 introduced important features like a virtual memory system, advanced networking capabilities, and improved security measures. It played a key role in shaping modern UNIX systems and influenced many other operating systems, including Linux, by providing a robust and flexible framework for multitasking and multi-user environments.