According to the U.S. Copyright Act, the purpose of copyright is a means for a creator or owner of a particular work to receive exclusive rights to reproduce, distribute, perform, display, or license the work. To be covered by copyright a work must be original and in a concrete "medium of expression." Currently, works will adhere to copyright whether or not the particular work in question is officially registered for copyright.
Modern application of copyright originated within Article I, Section 8 of The United States Constitution, as taken from the Preface to Copyright Law: "The Congress shall have Power ... To promote the Progress of Science and useful Arts, by securing for limited Times to Authors and Inventors the exclusive Right to their respective Writings and Discoveries."