DIAMOND v. DIEHR, 450 U.S. 175 (1981)

Abstract of the Decision
Facts: Diehr and Lutton invented an improved press that cured rubber by controlled heating. The press contained a temperature probe which measured the temperature rise of the rubber from within the press. By repeatedly calculating the rubber cure time from this temperature measurement and comparing this computed cure time to the actual elapsed time, the computer was able to determine precisely when to open the press and eject the cured rubber, which then emerged perfectly cured. The patent examiner, viewing all computer programs as unpatentable because of the earlier Supreme Court decision Gottschalk v. Benson (1972), rejected their patent application because, he argued, the inventors had simply combined an unpatentable program with a conventional rubber curing press. An appellate court reversed the Examiner and ordered a patent to issue. The Commissioner of Patents then petitioned to have the Supreme Court review this decision. Before the Supreme Court, the inventors argued that the steps of continuously measuring temperature and repeatedly recalculating the rubber cure time and comparing it to the elapsed time were new steps that were worthy of patent protection.
Question Presented: Can a patent be granted for a machine that physically transforms materials under the control of a programmed computer?
Conclusion: Yes. In a 5-to-4 decision, the court held that a machine which transforms materials physically under the control of a programmed computer is patentable. In addition, and without overruling the earlier Gottschalk v. Benson decision holding that a mathematical procedure cannot be patented, the majority in Diehr said the Benson decision did not render all computer programs unpatentable, contrary to what Justice John Paul Stevens argued in his strong dissenting opinion in Diehr. The Diehr court left undecided the question of whether computer programs standing by themselves could ever be patentable. Immediately following the Diehr ruling, software patent applications began flowing into the Patent Office in a steady stream that remains undiminished today.
Thirteen years later, the Court of Appeals for the Federal Circuit, in In re Alappat, ruled that virtually all computer programs are patentable.