Copyrights are meant to protect only the expression of an idea. Granting this protection is fairly staightforward for traditional forms of expression such as books and papers. Generally, an idea can be expressed in a book many ways, and only the one an author chooses to use is protected by copyright. However, when copyright law was extended to software in 1976, it became very unclear where the line would be drawn between idea and expression. More so than in books and papers, ideas and expressions in software are very closely linked - making this classification very difficult. Thus, the details of this form of protection are much less clear. To see how the distinctions have historically been drawn, it is important to examine the actions of the Courts, businesses, and administrative agencies.

The first case involving this issue was Whelan Associates vs. Jaslow Dental Laboratories. In this case, Jaslow Laboratories contracted with Whelan to develop and maintain a program for running dentist offices - called Dentalab. Whelan did this for several years. Then, Jaslow decided to create a new version of the software written in BASIC (for smaller computers). Even though this version was not a direct copy of their software, Whelan sued, arguing that Jaslow had violated their copyright. The courts agreed, saying that computer program copyrights could be infringed if the idea is imitated, not just if the literal source code is copied. As As Josef Drexl writes in his paper What is Protected in a Computer Program, this was the "most extensive scope of protection U.S. courts had ever accepted" and was adopted because "the need to induce the creation of new programs required protection of this structure" [7].

This precedent did not remain in effect for long, however. After this decision, the courts began moving away from protecting program ideas and toward more free competition. In 1990, a landmark case was decided that modified the criteria for protection. This case, Lotus Development Corp vs. Paperback Software International, was brought by Lotus because they felt that Paperback had copied their menu structure in Lotus123. In deciding the case, Judge Keeton made a careful argument that served as a new precedent. He stated that, in general, ideas are not copyrightable. He claims: "If, however, the expression of an idea has elements that go beyond all functional elements of the idea itself, and beyond the obvious, and if there are numerous other ways of expressing the non-copyrightable idea, then those elements of expression, if original and substantial, are copyrightable" [7]. Thus, general ideas such as spreadsheets were held to be uncopyrightable since they were not "non-obvious." However, the unique menu structure of Lotus 1-2-3 was protected under this analysis - and Paperback Software was found to be infringing on the copyright. (This will be discussed in more detail in the user interface section).

This precedent was further refined in the 1992 case of Computer Associates International vs. Altai Inc. In this case, Altai created a software package using code from Computer Associates. After Altai's executives found out that they were using copyrighted code, they rewrote those parts of the program using a "clean room" approach (a system where programmers are only given access to non-protected information). It was then up to the courts to decide whether this new version violated copyright. In deciding this case, the court came up with a three step test for copyright infringement. In the first step, abstraction, a program must be "dissect[ed] … [to] isolate each level of abstraction within it" [1]. Next, in the filtration step, the court must decide if elements were "ideas" or "considerations of efficiency." Finally, the comparison step involves comparing the two programs to see if any protectable ideas were copied. This test made it even more difficult to enforce copyright protection on software. According to this test, Altai was found not to have infringed on Computer Associates' copyright.

Thus, it is clear that the courts have been slowly retreating from the strong IP protection originally granted to software developers. As we will observe, this remains true as we look at important sub-issues the courts have faced related to software. Two of the most important such issues are: reverse engineering and user interfaces.