This document summarizes the evolution of operating systems from the first to fourth generations. The first generation from 1940-1950 involved manually loading programs to control computers without an operating system. The second generation from 1955-1965 introduced batch processing systems like GMOS. The third generation from 1965-1980 developed multiprogramming operating systems to serve multiple users simultaneously. The fourth generation from 1980 to present saw the rise of personal computers and graphical user interfaces, popular operating systems including Windows, Mac OS, and Linux. The history of operating systems over the past 50+ years has largely been determined by advances in hardware and the need to process increasing amounts of data more efficiently.