The operating systems I kown includes Android、IOS、 Windows、Mac、Linux.
The operating systems I have used includes Android and Windows 10.
Android is a free and open source operating system based on Linux it mainly used in mobile devices such as smart phones and tablet PCs. It has content providers、resource manager、notification manager and activity manager so it it convient and mystical for me when I use Android phone and apps in it is rich although IOS has some apps that Android