U.S. patent law Edit

The "function of a machine" objection rested upon the alleged failure of the applicant to disclose alternative ways of reaching a particular result. A related, but distinguishable, set of problems arose concerning the perception that certain claims are not confined to an appropriate set of end uses. These problems can be separated into those relating to "field of use" limitations and those relating to the qualities of disclosed end uses.

"Field of use" limitations are accomplished by reciting in a claim at least one process step which limits the claim to practice in a particular industrial or technological area. Such limitations have been thought by some to be both necessary and adequate to overcome subject matter difficulties, although the set of acceptable "field of use" candidates has not been well defined. Some who otherwise oppose program-related patents suggest that the "field of use" need not extend beyond the data processing industry, arguing that "system programs” or "control techniques" are patentable as steps in processes that begin and end with the manipulation of peripheral equipment.

The qualitative test for proper "end use" limitations typically relies on the language of Cochrane v. Deener,[1] which, it is argued, limited patentable processes to those which act to change specified materials to a "different state or thing."[2]

Processes which include steps of manipulating physical matter subsequent to computational steps avoid the Cochrane barrier. The critical issue has been whether internal computer processes are statutory under this test.

Patent proponents have attempted to avoid the application of Cochrane by arguing that program-related claims refer to changes in memory device states rather than to numerical manipulation, and by asserting that The Telephone Cases[3] established the equivalence of changes in substances and electromagnetic alterations for subject matter purposes. Proponents also claim that the "test" of Cochrane, whatever its original force, was altered by subsequent decisions and that "[a]s long as the process embodies physical materials, agents and effects, and produces a novel and useful result, it is patentable.” The Prater case was expected to settle the "acting on materials" issue and was said to have done so, although the statements to that effect in Prater II were simply obiter dicta. By the time of the Benson appeal, however, the Supreme Court was being asked to revive the Cochrane doctrine.


  1. 94 U.S. 780 (1876).
  2. That a process may be patentable, irrespective of the particular form of the instrumentalities used, cannot be disputed. If one of the steps of a process be that a certain substance is to be reduced to a powder, it may not be at all material what instrument or machinery is used to effect that object, whether a hammer, a pestle and mortar, or a mill. Either may be pointed out; but if the patent is not confined to that particular tool or machine, the use of the others would be an infringement, the general process being the same. A process is a mode of treatment of certain materials to produce a given result. It is an act, or a series of acts, performed upon the subject matter to be transformed and reduced to a different state or thing. Id. at 787-88.
  3. 126 U.S. 1 (1887).

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