Bitcoin is controlled by the Bitcoin users all over the world. While the developers of the program are making certain improvements from time to time, they cannot make any change in the protocol of Bitcoin as all of the users are free in their decision which software and version to use. However, for remaining compatible with each other the users should use the same system that has the same rules. This is really important as Bitcoin can only work when there is a certain consensus among the users. Thus, all of the users and developers need to protect this consensus so that they have a success in their work.