This document summarizes several types of operating systems: - Windows, the most popular system developed by Microsoft for PCs, with a graphical interface based on windows. Recent versions include Windows XP, Vista, 7, and 8. - Linux, an open-source system developed in 1990 that can be modified and distributed freely. It is multi-user and multi-tasking. - Unix, a multi-user, multi-tasking system developed in 1969 that runs on many platforms and influenced later systems like Linux and MacOS. - DOS, an early Microsoft operating system for PCs that preceded Windows. - Mac OS, the user-friendly system created by Apple for Macintosh computers to organize