17 U.S.C. § 102 : US Code - Section 102: Subject matter of copyright: In general

      (a) Copyright protection subsists, in accordance with this title,
    in original works of authorship fixed in any tangible medium of
    expression, now known or later developed, from which they can be
    perceived, reproduced, or otherwise communicated, either directly
    or with the aid of a machine or device. Works of authorship include
    the following categories:
        (1) literary works;
        (2) musical works, including any accompanying words;
        (3) dramatic works, including any accompanying music;
        (4) pantomimes and choreographic works;
        (5) pictorial, graphic, and sculptural works;
        (6) motion pictures and other audiovisual works;
        (7) sound recordings; and
        (8) architectural works.

      (b) In no case does copyright protection for an original work of
    authorship extend to any idea, procedure, process, system, method
    of operation, concept, principle, or discovery, regardless of the
    form in which it is described, explained, illustrated, or embodied
    in such work.