United States Court of Appeals for the Federal Circuit 

2007-1419 

ARISTOCRAT TECHNOLOGIES AUSTRALIA PTY LIMITED 

and ARISTOCRAT TECHNOLOGIES, INC., 

Plaintiffs-Appellants, 

v. 

INTERNATIONAL GAME TECHNOLOGY 

and IGT, 

Defendants-Appellees. 

Brian E. Ferguson, McDermott, Will & Emery LLP, of Washington, DC, argued for 

plaintiffs-appellants. With him on the brief was Amalie M. Weber. Of counsel on the 

brief were Terrence P. McMahon, Anthony R. De Alcuaz, and Robert J. Blanch, of Palo 

Alto, California. 

Jeffrey W. Sarles, Mayer Brown LLP, of Chicago, Illinois, argued for defendantsappellees. With him on the brief were Melissa A. Anyetei and Andrea C. Hutchison. 

 

Appealed from: United States District Court for the District of Nevada 

Judge Brian E. Sandoval 
United States Court of Appeals for the Federal Circuit 

2007-1419 

ARISTOCRAT TECHNOLOGIES AUSTRALIA PTY LIMITED 

and ARISTOCRAT TECHNOLOGIES, INC., 

Plaintiffs-Appellants, 

v. 

INTERNATIONAL GAME TECHNOLOGY 

and IGT, 

Defendants-Appellees. 

Appeal from the United States District Court for the District of Nevada in 

case no. 05-CV-820, Judge Brian E. Sandoval. 

___________________________ 

DECIDED: March 28, 2008 

___________________________ 

Before LOURIE, SCHALL, and BRYSON, Circuit Judges. 

BRYSON, Circuit Judge. 

The appellants, referred to collectively as “Aristocrat,” are the owner and 

exclusive licensee of U.S. Patent No. 6,093,102 (“the ’102 patent”). The patent is 

directed to an electronic slot machine that allows a player to select winning 

combinations of symbol positions. The appellees, referred to collectively as “IGT,” 

manufacture and sell gaming products that Aristocrat asserts infringe the ’102 patent. 

In an infringement action brought by Aristocrat against IGT in the United States District 

Court for the District of Nevada, the district court held all of the claims of the ’102 patent 

invalid for indefiniteness.
The game disclosed in the ’102 patent purportedly increases player interest in 

slot machines by providing the player with greater control over the definition of winning 

opportunities. It allows the player to define the winning opportunities based on symbols 

displayed on the top and side of a multi-line screen representing slot machine reels. 

Using the invention on a 3x5 screen, for example, the player can define numerous 

different arrangements that will allow the player to win for some subset of the 243 

possible winning combinations. The player can do so by selecting symbol positions and 

thereby activating winning opportunities for combinations in which the symbols are not 

necessarily aligned with one another. The only constraint is that the selected 

combination must contain at least one symbol from each column. Figure 2 from the 

’102 patent shows a 3x5 screen with selections, and the figure on the right shows one of 

the winning combinations for the selection in Figure 2. 

A winning combination 

On summary judgment, the trial court held all of the claims of the ’102 patent 

invalid. Aristocrat does not dispute that all of the claims rise and fall together. Like the 

parties, we therefore focus on independent claim 1. 

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2007-1419 3 

 Claim 1 reads as follows: 

A gaming machine 

having display means arranged to display a plurality of symbols in a 

display format having an array of n rows and m columns of symbol 

positions, 

game control means arranged to control images displayed on the display 

means, 

 

the game control means being arranged to pay a prize when a 

predetermined combination of symbols is displayed in a 

predetermined arrangement of symbol positions selected by a 

player, playing a game, including one and only one symbol position 

in each column of the array, 

 

the gaming machine being characterised in that selection means are 

provided to enable the player to control a definition of one or more 

predetermined arrangements by selecting one or more of the 

symbol positions and 

 

the control means defining a set of predetermined arrangements for a 

current game comprising each possible combination of the symbol 

positions selected by the player which have one and only one 

symbol position in each column of the display means, 

 

wherein the number of said predetermined arrangements for any one 

game is a value which is the product k1 . . . x . . . ki . . . x . . . km

where ki is a number of symbol positions which have been selected 

by the player in an ith column of the n rows by m columns of symbol 

positions on the display (0 < i ≤ m and ki ≤ n). 

I 

The district court observed that the key question in this case is the definiteness of 

the claim term “game control means” or “control means” that is used several times in 

claim 1. The court explained that the claim describes the “game control means” as 

performing three functions: (1) to control images displayed on the display means; (2) to 

pay a prize when a predetermined combination of symbols matches the symbol 
2007-1419 4 

positions selected by the player; and (3) to define the pay lines for the game according 

to each possible combination of the selected symbol positions. 

The district court noted that the parties agreed the term “control means” is a 

means-plus-function term that invokes 35 U.S.C. § 112 ¶ 6. As such, the scope of that 

claim limitation had to be defined by the structure disclosed in the specification plus any 

equivalents of that structure; in the absence of structure disclosed in the specification to 

perform those functions, the claim limitation would lack specificity, rendering the claim 

as a whole invalid for indefiniteness under 35 U.S.C. § 112 ¶ 2. See In re Donaldson, 

16 F.3d 1189, 1195 (Fed. Cir. 1994) (en banc). 

The court noted that there were slight linguistic differences in the parties’ 

characterizations of the functions performed by the “control means,” but that the 

differences were unimportant, because there was no adequate disclosure of structure in 

the specification to perform those functions, regardless of how they were defined. 

Although Aristocrat argued that the structure corresponding to the recited functions was 

a standard microprocessor-based gaming machine with “appropriate programming,” the 

court noted that the specification contained no “guidance to determine the meaning of 

‘standard microprocessor’ or ‘appropriate programming.’” The court ruled that “[m]erely 

stating that a standard microprocessor is the structure without more is not sufficient.” In 

particular, the court noted that the specification did not create any specific structure or 

new machine because “it does not set forth any specific algorithm” for performing the 

recited function. 

Citing decisions of this court, the trial court explained that in a means-plusfunction claim “in which the disclosed structure is a computer or a microprocessor 
2007-1419 5 

programmed to carry out an algorithm, a corresponding structure must be a specific 

algorithm disclosed in the specification, rather than merely ‘an algorithm executed by a 

computer.’” Because the specification of the ’102 patent lacks “any specific algorithm” 

or any “step-by-step process for performing the claimed functions of controlling images 

on the slot machines [sic] video screen, paying a prize when a predetermined 

combination of symbols comes up or defining the pay lines for games,” the court held 

the asserted structure to be insufficient to satisfy section 112 paragraph 6. In addition, 

the district court held that the specification did not link the asserted structure to any of 

the claimed functions. The court held claim 1 invalid for that reason as well. 

II 

On appeal, Aristocrat first argues that the district court erred by failing to construe 

the disputed term “game control means” or “control means” in claim 1. Aristocrat 

argues that because the district court did not construe the functions of the “control 

means” term under 35 U.S.C. §112 ¶ 6, it could not have properly determined whether 

the specification recited adequate structure corresponding to those functions. 

The district court stated that “[t]he determination as to which function description 

is the accurate construction is not pertinent to the summary judgment motion because 

the structure is lacking in description and is not found in the specification.” Aristocrat 

argues that our decision in Oakley, Inc. v. Sunglass Hut Int’l, 316 F.3d 1331, 1340 (Fed. 

Cir. 2003), requires that a “determination [of definiteness] requires a construction of the 

claims according to the familiar canons of claim construction.” 

The district court committed no error in its analysis of the means-plus-function 

limitation in this case. The court described the two competing claim constructions 
2007-1419 6 

proposed by the parties, and the court’s description made clear that there was virtually 

no difference between them. Moreover, the district court, later in its opinion, effectively 

gave a construction of the functions of the “control means” limitation when it stated that 

the specification contained no algorithm that described or recited the claimed functions. 

Describing the claimed functions, the court wrote: “The specification contains no stepby-step process for performing the claimed functions of controlling images on the slot 

machine’s video screen, paying a prize when a predetermined combination of symbols 

comes up or defining the pay lines for games.” That characterization of the claimed 

functions of the “game control means” is not materially different from the 

characterization that Aristocrat argues the district court should have adopted in 

analyzing the means-plus-function limitation. To the extent the court’s characterization 

differs from Aristocrat’s, it is only because the court’s characterization omits some of the 

detail found in Aristocrat’s characterization. The omission of that detail, however, has 

no effect on the question whether the specification discloses sufficient structure to 

perform the claimed functions. In fact, Aristocrat’s description of the claimed function 

would appear to require more by way of specificity in the disclosed structure than would 

the court’s characterization. The district court therefore committed no reversible error 

with respect to this issue. 

III 

Aristocrat’s principal contention is that the district court was wrong to hold that 

the patent’s disclosure of a general purpose, programmable microprocessor was not a 

sufficient disclosure of structure to satisfy section 112 paragraph 6. In particular, 

Aristocrat argues that computer-implemented means-plus-function claims do not require 
2007-1419 7 

disclosure of a corresponding algorithm, as held by the district court. Instead, Aristocrat 

contends that the structure disclosed in the specification of the ’102 patent, which was 

simply “any standard microprocessor base [sic] gaming machine [with] appropriate 

programming,” was a sufficient disclosure of structure under this court’s precedents. 

In cases involving a computer-implemented invention in which the inventor has 

invoked means-plus-function claiming, this court has consistently required that the 

structure disclosed in the specification be more than simply a general purpose computer 

or microprocessor. The point of the requirement that the patentee disclose particular 

structure in the specification and that the scope of the patent claims be limited to that 

structure and its equivalents is to avoid pure functional claiming. As this court explained 

in Medical Instrumentation & Diagnostics Corp. v. Elekta AB, 344 F.3d 1205, 1211 (Fed. 

Cir. 2003), “If the specification is not clear as to the structure that the patentee intends 

to correspond to the claimed function, then the patentee has not paid the price but is 

attempting to claim in functional terms unbounded by any reference to structure in the 

specification.” See also Biomedino, LLC v. Waters Techs. Corp., 490 F.3d 946, 948 

(Fed. Cir. 2007) (“[I]n return for generic claiming ability, the applicant must indicate in 

the specification what structure constitutes the means.”). For a patentee to claim a 

means for performing a particular function and then to disclose only a general purpose 

computer as the structure designed to perform that function amounts to pure functional 

claiming. Because general purpose computers can be programmed to perform very 

different tasks in very different ways, simply disclosing a computer as the structure 

designated to perform a particular function does not limit the scope of the claim to “the 
2007-1419 8 

corresponding structure, material, or acts” that perform the function, as required by 

section 112 paragraph 6. 

 That was the point made by this court in WMS Gaming, Inc. v. International 

Game Technology, 184 F.3d 1339 (Fed. Cir. 1999). In that case, the court criticized the 

district court, which had determined that the structure disclosed in the specification to 

perform the claimed function was “an algorithm executed by a computer.” The district 

court erred, this court held, “by failing to limit the claim to the algorithm disclosed in the 

specification.” Id. at 1348. The rationale for that decision is equally applicable here: a 

general purpose computer programmed to carry out a particular algorithm creates a 

“new machine” because a general purpose computer “in effect becomes a special 

purpose computer once it is programmed to perform particular functions pursuant to 

instructions from program software.” Id., quoting In re Alappat, 33 F.3d 1526, 1545 

(Fed. Cir. 1994). The instructions of the software program in effect “create a special 

purpose machine for carrying out the particular algorithm.” WMS Gaming, 184 F.3d at 

1348. Thus, in a means-plus-function claim “in which the disclosed structure is a 

computer, or microprocessor, programmed to carry out an algorithm, the disclosed 

structure is not the general purpose computer, but rather the special purpose computer 

programmed to perform the disclosed algorithm.” Id. at 1349. 

In a later case, this court made the same point, stating that a “computerimplemented means-plus-function term is limited to the corresponding structure 

disclosed in the specification and equivalents thereof, and the corresponding structure 

is the algorithm.” Harris Corp. v. Ericsson Inc., 417 F.3d 1241, 1253 (Fed. Cir. 2005). 

The court in that case characterized the rule of WMS Gaming as follows: “[T]he 
2007-1419 9 

corresponding structure for a § 112 ¶ 6 claim for a computer-implemented function is 

the algorithm disclosed in the specification.” 417 F.3d at 1249. 

 In this case, Aristocrat acknowledges that the only portion of the specification 

that describes the structure corresponding to the three functions performed by the 

“control means” is the statement that it is within the capability of a worker in the art “to 

introduce the methodology on any standard microprocessor base [sic] gaming machine 

by means of appropriate programming.” ’102 patent, col. 3, ll. 2-4. That description 

goes no farther than saying that the claimed functions are performed by a general 

purpose computer. The reference to “appropriate programming” imposes no limitation 

whatever, as any general purpose computer must be programmed. The term 

“appropriate programming” simply references a computer that is programmed so that it 

performs the function in question, which is to say that the function is performed by a 

computer that is capable of performing the function. 

 Aristocrat offers two responses to the district court’s conclusion that the patent 

did not disclose sufficient structure. First, Aristocrat argues that the specification 

disclosed algorithms that were sufficient to constitute a qualifying disclosure of 

structure. Second, Aristocrat argues that no disclosure of specific algorithms was 

necessary in any event. 

A 

 As to the first argument, Aristocrat contends that the language of claim 1 

referring to “the game control means being arranged to pay a prize when a 

predetermined combination of symbols is displayed in a predetermined arrangement of 

symbol positions selected by a player” implicitly discloses an algorithm for the 
2007-1419 10 

microprocessor. That is, when the winning combination of symbols is displayed, the 

program should pay a prize. But that language simply describes the function to be 

performed, not the algorithm by which it is performed. Aristocrat’s real point is that 

devising an algorithm to perform that function would be within the capability of one of 

skill in the art, and therefore it was not necessary for the patent to designate any 

particular algorithm to perform the claimed function. As we have noted above, however, 

that argument is contrary to this court’s law. 

 Aristocrat also points to language in claim 1 that, according to Aristocrat, “sets 

forth the mathematical equation that describes the result of practicing the third function.” 

The language in question recites “defining a set of predetermined arrangements for a 

current game comprising each possible combination of the symbol position selected by 

the player which have one and only one symbol position in each column of the display 

means.” The problem with Aristocrat’s argument is underscored by Aristocrat’s very 

characterization of the role of the equation: It describes the result of practicing the third 

function. That is, the equation is not an algorithm that describes how the function is 

performed, but is merely a mathematical expression that describes the outcome of 

performing the function. To be sure, as Aristocrat argues, the equation “restricts 

‘appropriate programming’ to algorithms which result in the specified number of winning 

opportunities.” But that argument simply concedes that the equation describes an 

outcome, not a means for achieving that outcome. The equation thus does not disclose 

the structure of the claimed device, but is only another way of describing the claimed 

function. 
 Finally, Aristocrat contends that “the written description delineates what 

constitutes ‘appropriate programming’ through the disclosed embodiments of the 

invention.” Again, however, the description of the embodiments is simply a description 

of the outcome of the claimed functions, not a description of the structure, i.e., the 

computer programmed to execute a particular algorithm. 

In making this argument, Aristocrat relies on Figure 1 and Table 1 from the 

patent, which provide examples of how player selections translate to possible winning 

combinations: 

Two other pairs of figures and tables, Figures 3 and 4, and Tables 2 and 3, offer 

similar examples. The corresponding portion of the written description contains 

mathematical descriptions of how many winning combinations would be produced. ’102 

patent, col. 3, line 54, through col. 5, line 21. Aristocrat refers to these examples as 

“algorithms.” The figures, tables, and related discussion, however, are not algorithms. 

They are simply examples of the results of the operation of an unspecified algorithm. 

Like the mathematical equation set forth in claim 1, these combinations of figures and 

2007-1419 11 
2007-1419 12 

tables are, at best, a description of the claimed function of the means-plus-function 

claim. 

Aristocrat has elected to claim using section 112 paragraph 6 and therefore must 

disclose corresponding structure. It has disclosed, at most, pictoral and mathematical 

ways of describing the claimed function of the game control means. That is not enough 

to transform the disclosure of a general-purpose microprocessor into the disclosure of 

sufficient structure to satisfy section 112 paragraph 6. 

B 

In support of the contention that it is not necessary to disclose a particular 

algorithm in order to disclose sufficient structure for a means-plus-function limitation in a 

computer-implemented invention, Aristocrat relies primarily on In re Dossel, 115 F.3d 

942 (Fed. Cir. 1997). Aristocrat argues that the application in Dossel did not disclose a 

particular algorithm, and that the court held the disclosure sufficient even though the 

application stated, with respect to the performance of one of the claimed functions, that 

“[k]nown algorithms can be used for this purpose.” 

The means-plus-function limitation at issue in Dossel was a “means for 

reconstructing the current distribution” on the surface of an element inside a biological 

object, such as on the surface of a tumor inside a human brain. The application stated 

that the reconstruction unit would reconstruct the density of the current at various points 

on that surface from the values of the magnetic flux density at corresponding pixels at 

the same time. See U.S. Patent No. 5,885,215, col. 4, ll. 6-10 (the patent that issued 

from the Dossel application). The application explained that “[k]nown algorithms can be 

used for this purpose.” Id., col. 4, ll. 10-11. The application then provided the particular 
2007-1419 13 

equation by which the relationship between the values of magnetic flux density and 

current density could be described in matrix form, id., col. 4, ll. 12-15, and it described in 

great detail the components of that equation, id., col. 4, ll. 16-55. Accordingly, while 

providing a detailed explanation of how the claimed device would perform the claimed 

function, the specification left the mathematical techniques used to solve the recited 

equations to persons of ordinary skill in the art. That is what this court referred to when 

it stated that the application stated “that ‘known algorithms’ can be used to solve 

standard equations which are known in the art.” Dossel, 115 F.3d at 946. 

From the context and from reviewing the application, it is clear that the Dossel

court used the term “algorithm” in a narrow sense, referring to particular well-known 

mathematical operations that could be used to solve the equations disclosed in the 

application. Far from supporting Aristocrat’s claim that a reference to a general purpose 

computer with “appropriate programming” discloses sufficient structure for section 112 

paragraph 6, the Dossel case provides an example of an extremely detailed disclosure 

of all information necessary to perform the function, except for basic mathematical 

techniques that would be known to any person skilled in the pertinent art. 

Aristocrat also argues that, even if there is no disclosure of an algorithm in the 

patent, the disclosure of a microprocessor with “appropriate programming” is a sufficient 

disclosure of structure for means-plus-function purposes, because the evidence showed 

that one of ordinary skill in the art could build the device claimed in the ’102 patent 

based on the disclosure in the specification. That argument, however, conflates the 

requirement of enablement under section 112 paragraph 1 and the requirement to 

disclose the structure that performs the claimed function under section 112 paragraph 6. 
2007-1419 14 

Although the examples given in the ’102 patent might enable one of ordinary skill to 

make and use the invention, they do not recite the particular structure that performs the 

function and to which the means-plus-function claim is necessarily limited. 

Whether the disclosure would enable one of ordinary skill in the art to make and 

use the invention is not at issue here. Instead, the pertinent question in this case is 

whether Aristocrat’s patent discloses structure that is used to perform the claimed 

function. Enablement of a device requires only the disclosure of sufficient information 

so that a person of ordinary skill in the art could make and use the device. A section 

112 paragraph 6 disclosure, however, serves the very different purpose of limiting the 

scope of the claim to the particular structure disclosed, together with equivalents. The 

difference between the two is made clear by an exchange at oral argument. In 

response to a question from the court, Aristocrat’s counsel contended that, in light of the 

breadth of the disclosure in the specification, any microprocessor, regardless of how it 

was programmed, would infringe claim 1 if it performed the claimed functions recited in 

the means-plus-function limitations of that claim. That response reveals that Aristocrat 

is in essence arguing for pure functional claiming as long as the function is performed 

by a general purpose computer. This court’s cases flatly reject that position. 

For example, in Atmel Corp. v. Information Storage Devices, Inc., 198 F.3d 1374, 

1380 (Fed. Cir. 1999), the court embraced the proposition that “consideration of the 

understanding of one skilled in the art in no way relieves the patentee of adequately 

disclosing sufficient structure in the specification.” It is not enough for the patentee 

simply to state or later argue that persons of ordinary skill in the art would know what 

structures to use to accomplish the claimed function. The court in Biomedino, LLC v. 
2007-1419 15 

Waters Technologies Corp., 490 F.3d 946, 953 (Fed. Cir. 2007), put the point this way: 

“The inquiry is whether one of skill in the art would understand the specification itself to 

disclose a structure, not simply whether that person would be capable of implementing 

that structure.” Discussing Atmel, the court in Biomedino stated: 

In Atmel, it was not the fact that one skilled in the art was aware of 

known circuit techniques that resulted in a conclusion that sufficient 

structure was recited. Rather, it was the inclusion in the written 

description of the title of [a technical article] which itself described the 

structure for a “known circuit technique.” Expert testimony was used to 

show what the title of the article would convey to one skilled in the art—in 

this case it was the “precise structure of the means recited in the 

specification.” . . . The expert’s testimony did not create or infer the 

structure. 

490 F.3d at 952. 

Aristocrat relies on a statement from the recent decision of this court in AllVoice 

Computing PLC v. Nuance Communs., Inc., 504 F.3d 1236, 1245 (Fed. Cir. 2007), 

where the court stated that in software cases “algorithms in the specification need only 

disclose adequate defining structure to render the bounds of the claim understandable 

to one of ordinary skill in the art.” We similarly stated in Medical Instrumentation & 

Diagnostics Corp. v. Elekta AB, 344 F.3d 1205, 1214 (Fed. Cir. 2003), that “there would 

be no need for a disclosure of the specific program code if software were linked to 

the . . . function and one skilled in the art would know the kind of program to use.” 

It is certainly true that the sufficiency of the disclosure of algorithmic structure 

must be judged in light of what one of ordinary skill in the art would understand the 

disclosure to impart. See, e.g., Intel Corp. v. VIA Techs., 319 F.3d 1357, 1367 (Fed. 

Cir. 2003) (knowledge of a person of ordinary skill in the art can be used to make clear 

how to implement a disclosed algorithm); Atmel Corp., 198 F.3d at 1379 (“[T]he ‘one 
2007-1419 16 

skilled in the art’ analysis should apply in determining whether sufficient structure has 

been disclosed to support a means-plus-function limitation.”). That principle, however, 

has no application here, because in this case there was no algorithm at all disclosed in 

the specification. The question thus is not whether the algorithm that was disclosed 

was described with sufficient specificity, but whether an algorithm was disclosed at all. 

In Medical Instrumentation, we held that the proper inquiry for purposes of 

section 112 paragraph 6 analysis is to “look at the disclosure of the patent and 

determine if one of skill in the art would have understood that disclosure to encompass 

software [to perform the function] and been able to implement such a program, not 

simply whether one of skill in the art would have been able to write such a software 

program.” 344 F.3d at 1212 (emphasis in original). We then stated that it is “not proper 

to look to the knowledge of one skilled in the art apart from and unconnected to the 

disclosure of the patent.” Id. That is precisely the inquiry the district court performed 

and that we reviewed above. Here, as in Medical Instrumentation, the patent does not 

disclose the required algorithm or algorithms, and a person of ordinary skill in the art 

would not recognize the patent as disclosing any algorithm at all. Accordingly, the 

means-plus-function limitations of claim 1 lacked sufficient disclosure of structure under 

35 U.S.C. § 112 ¶ 6 and were therefore indefinite under 35 U.S.C. § 112 ¶ 2. 

IV 

Aristocrat was not required to produce a listing of source code or a highly 

detailed description of the algorithm to be used to achieve the claimed functions in order 

to satisfy 35 U.S.C. § 112 ¶ 6. It was required, however, to at least disclose the 

algorithm that transforms the general purpose microprocessor to a “special purpose 
2007-1419 17 

computer programmed to perform the disclosed algorithm.” WMS Gaming, 184 F.3d at 

1349. Because the district court correctly held that was not done in this case, we 

uphold the judgment of the district court. 

AFFIRMED.