Since Linux is a collaborative development environment, everyone that has contributed to the project has usually written some of the documentation.
The users and developers.
Members of the Linux Documentation Project. Individual package maintainers write manual pages for their software.
every one who likes to help linux
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By configuring the bootloader to use Windows as the default menu option instead of Linux. Refer to documentation on how to do this.
Many distributions have documentation or builtin graphical installation utilities.
Linux was created in 1991 by a Finnish college student named Linus Torvalds.
The 'man' or the 'info' command have documentation about utilities and commands in the system.
Man (or manual) pages
You can find free eBooks on Linux through various online platforms such as Project Gutenberg, which offers a selection of public domain books, and websites like FreeTechBooks, which specifically lists free computer science and programming books. Additionally, the official documentation and guides from the Linux Documentation Project (tldp.org) provide comprehensive resources. GitHub repositories and online forums like Reddit also feature links to free Linux eBooks shared by the community.
Most screensavers on Linux are modules run by Xscreensaver: http://en.wikipedia.org/wiki/XScreenSaver I don't know exactly how to convert a program to a module, check the Xscreensaver documentation.