What is Windows operating system and why it is called Windows?

An operating system (OS) is software, consisting of programs and data, that runs on computers, manages computer hardware resources, & provides common services for execution of various application software. For hardware functions such as input & output and memory allocation, the operating system acts as an intermediary between application programs & the computer hardware. Operating systems are found on almost any device that contains a computer from cellular phones and video game consoles to supercomputers and web servers. Examples of popular modern operating systems for personal computers are: Mac OS X, Microsoft Windows & Linux.