Personal computer operating system provides a good interface to a single user.
Personal computer operating systems are widely used for word processing, spreadsheets and Internet access.
Personal computer operating system are made only for personal.
You can say that your laptops, computer systems, tablets etc. are your personal computers and the operating system such as windows 7, windows 10, android, etc. are your personal computer operating system.
And you can use your personal computer operating system for your personal purposes, for example, to chatting with your friends using some social media sites, reading some articles from internet, making some projects through microsoft powerpoint or any other, designing your website, programming something, watching some videos and movies, listening to some songs and many more.