A copyright is a form of legal protection that allows the author of an original work and his/her heirs to enforce exclusive rights over publication, distribution and adaptation for a certain period of time. Although copyright legislation differs from country to country, international treaties exist that enforce generally consistent copyright legislation throughout most of the world. Below is a description of the generally accepted features of copyright legislation.
What copyright legislation protects
Copyright legislation was originally designed to protect literary, musical and artistic works, and has recently been extended to protect computer programs. From a legal standpoint, copyright law protects expressions of ideas but not the ideas themselves. A description of a machine, for example, might be copyrightable, but this would protect only the description, not the machine itself (the machine might be eligible for patent protection, however).
Duration of protection
The duration of copyright protection varies with legal jurisdiction, type of work, and authorship. Most jurisdictions, for example, protect literary works for 50 to 100 years after the death of the author. Under certain circumstances, copyright protection extends for a certain number of years after its creation, and under other circumstances the "copyright clock" starts to run only when the work is published. After the period of copyright protection expires, the work is said to enter the "public domain," meaning that the proprietary rights of the author (or his/her heirs) with respect to the work have permanently expired. For example, Shakespeare's heirs could not sue Universal Studios for making a film using lines from "Hamlet."
Obtaining copyright protection
In most jurisdictions, copyright protection attaches automatically as soon as an original work is created (as soon as a manuscript is created, for example, regardless of whether it is ever published). As a practical matter, however, almost all copyright legislation provides for a system of copyright registration to allow authors to prove their authorship against "copycats." An employee who creates an original work incident to employment may find his work classified as a "work for hire" that belongs to the employer, not the employee.
Limitations on protection
The "Fair Use" doctrine allows the use of a limited amount of copyrighted material as long as it is attributed to the copyright owner. For example, it is generally considered acceptable for a book author to quote a single line from a copyrighted song, as long as the quote is attributed to the copyright owner (the author, in most cases). However, it is unclear in most jurisdictions exactly how much of a copyrighted work can be used under the Fair Use doctrine, because this depends on many factors. The "First Sale" doctrine allows a legitimate purchaser of a copyrighted work to sell the work to a third party without penalty. For example, second-hand bookstores do not need to obtain permission from the author before selling copyrighted works to the general public.
The Berne Convention for the Protection of Literary and Artistic Works is by far the most prominent of several international multilateral treaties dealing with the subject of copyrights. The Berne Convention provides for mutual recognition of copyrights among all nations that signed the Berne Convention, for example, a song written by a UK author would automatically be protected in all Berne Convention countries. Although most countries in the world are signatory to the Berne Convention, the United States and the United Kingdom did not participate until the late 1980s.