In re Bilski and Gottschalk v. Benson
It is important to remember that the Supreme Court's decision in Gottschalk v. Benson is still controlling law. In that 1972 decision, the Supreme Court held unpatentable a method of converting a signal from "binary coded decimal" into "binary." The Benson method operates by using a "reentrant shift register" – a particular electronic memory circuit of the day. The rejected claim reads as follows:
8. The method of converting signals from binary coded decimal form into binary which comprises the steps of:
In Bilski, the en banc court struggles with Benson because – on its face – the rejected Claim 8 from Benson satisfies the machine-or-transformation test of Bilski. The claimed BCD conversion method is tied to a particular machine. The Bilski majority admits as much: "the claimed process operated on a machine, a digital computer, but was still held to be ineligible subject matter." According to the en banc panel however Benson's claim still fails the machine-or-transformation test because the claimed physical limits were "not actually limiting." In particular, since the only uses of the BCD converter would be on a computer, tying the claims to a computer offered no practical limitation to the otherwise preemptive claim of an algorithm.
"[I]n Benson, the limitations tying the process to a computer were not actually limiting because the fundamental principle at issue, a particular algorithm, had no utility other than operating on a digital computer."
Thus under Bilski/Benson, tying a software algorithm to particular computer hardware may well be unpatentable subject matter if the patent would still preclude all practical uses of the otherwise unpatentable algorithm.
- Patently-Unobvious suggests that careful drafting could have avoided the whole problem for Benson: "If only the inventors had been less forthcoming, more obtuse, and called their claim a method for operating a shift register, who would have seen that the machine-implemented signal processing method surprisingly also happens to convert a binary coded decimal signal into a binary coded one?"