Recent developments in statutory and case law in the USA now make it possible to protect by copyright, proprietary computer programs from unauthorized copying provided that the copyright-holding party attempts to display the copyright notice publicly. Considerable progress has been made toward patentable computer software, but the issue of whether a computer program itself may be patented still remains unresolved. The Patent and Trademark Office (PTO) and the Court of Customs and Appeals (CCPA) have agreed that the application of a computer program, containing a mathematical algorithm, in a process may constitute patentible subject matter. The cases pertaining to copyrightable and patentable software together with an explanation of the wording of the new Section 117 of the 1976 Copyright Act are shown in the Appendixes to the article. The paper presents the issues pertaining to copyright and patent protection of computer software and some relevant cases for each issue. It concludes with a discussion of unresolved questions in protecting proprietary software.