The concept of copyright was conceived before the typewriter existed, much less the computer. On the other hand, the essence of copyright can be reduced to common sense for the majority of situations - if you're saving money by copying something, it's likely that you're violating copyright.
It is important to realize that the original copyright legislation was not phrased as a prohibition, but rather as a positive measure to encourage creativity by ensuring that it be rewarded. Our forefathers felt that this protection was so important that it was included in Article I of the Constitution (between establishing the Post Office and provisions for punishing pirates).
Copyright was a fairly simple concept as long as print was the most significant media, movies were watched in theatres, and music played on phonograph records. The simplicity disappeared when digital technology and the World Wide Web obliterated the status quo. The murky waters were further clouded by the variety of sources of copyright regulation. Copyright restrictions may emanate from Congress, from the Department of Copyright (Library of Congress), from court decisions, and even from independent committees.