I am writing open-source code based on another author's open-source code. The original author licensed the code under the GNU Public License and copyrighted it under his name. I am, of course, retaining the original license and won't remove his name.
However, I'm confused as to whether I can now copyright the code under my name, if it's already copyrighted under his name. How is this usually written in the code? For example, do I do this?
Copyright (C) 2013 "Original Author" Copyright (C) 2020 "Me" This program is free software... etc
Or does the copyright belong solely to the original author unless I change it completely?