The Copyright Symbol © is not mandatory to use in the European Union law, but many people use it to show that the creation or content is protected by the copyright law and having a certificate protection certificate certified by public notary.
Bern convention on Copyright : Authors of literary and artistic works are protected by the Bern Convention shall enjoy the exclusive right of making and of authorizing the translation of their works throughout the term of protection of their rights in the original works.
To represent the © symbol in HTML your need to use ©
On any other software you must press ALT and press 0169 in your numeric pad, it will show the copyright symbol as well.
The copyright symbol can be used on any digital or paper content but must be associated by real proof of copyright. Copyright.co.uk provide you the possibility to register your work online in realtime, your copyright will be recognized in 168 countries of the Bern Convention.
Below please find some copyright symbol in images :