United States: With Software Patents And Means-Plus-Function, "Structure" Takes On A New Meaning

Functional Claiming in Software Patents

Software patents are generally directed to a sequence of steps or rules, i.e., an algorithm, performed by a computer programmed to carry out the algorithm.  Because algorithms are inherently functional in nature, software patent claims are frequently written using functional, as opposed to structural, terms.  In many cases, software claims recite vague sounding "units" or "modules" to carry out steps of the algorithm.

Consequently, software claims are often subject to the means-plus-function guidelines set forth in 35 U.S.C. §112(f), which require that the specification describes structure to perform the claimed function.  Although a computer-implemented algorithm is necessarily executed using structural parts—e.g., a microprocessor, a memory, etc.—a description of such parts in the specification, on its own, may not suffice as the structure needed to satisfy 35 U.S.C. §112(f) and protect the claims from indefiniteness.

What is Means-Plus-Function?

According to 35 U.S.C. §112(f) (formerly 35 U.S.C. §112, sixth paragraph), "[a]n element in a claim for a combination may be expressed as a means or step for performing a specified function without the recital of structure, material, or acts in support thereof, and such claim shall be construed to cover the corresponding structure, material, or acts described in the specification and equivalents thereof."  Claim limitations invoking 35 U.S.C. §112(f) are commonly referred to as "means-plus-function" limitations.

A three-part test for identifying a means-plus-function limitation is set forth in MPEP §2181(I):

  1. the claim limitation uses the term "means," "step," or other term that is a generic placeholder for performing the claimed function;
  2. the term "means," "step," or other generic placeholder is modified by functional language, often (but not always) linked by a transition word (e.g., "for") or phrase (e.g., "configured to" or "so that"); and
  3. the term "means," "step," or other generic placeholder is not modified by sufficient structure, material, or acts for performing the claimed function.

When a claim limitation is deemed to invoke means-plus-function, corresponding structure must be disclosed in the specification itself in a way that one skilled in the art will understand what structure (or material or acts) will perform the recited function. See Atmel Corp. v. Information Storage Devices, Inc., 198 F.3d 1374, 1381, 53 USPQ2d 1225, 1230 (Fed. Cir. 1999).  If there is no such disclosure of structure for performing the recited function, the claim is rendered indefinite under 35 U.S.C. §112(b). See MPEP §2181(II)(A).

The Special Case of Computer-Implemented Means-Plus-Function Limitations

In the case of software patents, the claimed subject matter generally includes a series of computer-implemented steps, often invoking means-plus-function.  At first, one might assume that a computer, a microprocessor, or the like constitutes structure corresponding to the claimed function.  While technically accurate, for the purposes of 35 U.S.C. §112(f), the corresponding structure is (almost always) not a general purpose computer by itself, but rather the algorithm for carrying out the claimed function.

In Aristocrat Techs. Australia PTY Ltd. v. Int'l Game Tech., the court held that the structure corresponding to a 35 U.S.C. §112(f) limitation for a computer-implemented function "must include the algorithm needed to transform the general purpose computer or microprocessor disclosed in the specification" to a "special purpose computer" programmed to perform the claimed function. See Aristocrat, 521 F.3d at 1333, 86 USPQ2d at 1239.  The court stated that claiming a means for performing a specific computer-implemented function, without sufficiently disclosing the algorithm to perform that function, amounts to "pure functional claiming" and warrants a rejection for indefiniteness under 35 U.S.C. §112(b). See Aristocrat, 521 F.3d 1328 at 1333, 86 USPQ2d at 1239.

The sufficiency of the disclosed algorithm is determined in view of what a person of ordinary skill in the art would understand as sufficient to make the boundaries of the claim understandable. See Noah Systems Inc. v. Intuit Inc., 675 F.3d at 1313, 102 USPQ2d at 1417.  The algorithm must be disclosed in a degree of detail such that a person of ordinary skill in the art would know how to program the computer to achieve the claimed function. See Aristocrat, 521 F.3d at 1338, 86 USPQ2d at 1242. For example, it is not sufficient to merely reference a specialized computer (e.g., a "bank computer"), some undefined component of a computer system (e.g., "access control manager"), "logic," "program instructions," or other element that is essentially a black box intended to perform the recited function. See Blackboard, Inc. v. Desire2Learn, Inc., 574 F.3d 1371, 1383-85, 91 USPQ2d 1481, 1491-93 (Fed. Cir. 2009).  The court in Blackboard held that simply repeating the claimed functions in the specification is not a sufficient disclosure for an algorithm which, by definition, must contain a sequence of steps. See Blackboard, 574 F.3d at 1384, 91 USPQ2d at 1492.  In other words, there must be some explanation of how the computer or computer component performs the claimed function; or else such disclosure is akin to disclosing only a general purpose computer.

It should be noted there are certain circumstances where disclosing only a general purpose computer is sufficient for 35 U.S.C. §112(f) purposes.  In In re Katz Interactive Call Processing Patent Litigation, 639 F.3d 1303, 1316, 97 USPQ2d 1737, 1747 (Fed. Cir. 2011), the court identified an exception to the guidelines above in which a general purpose computer may be sufficient as the corresponding structure if the claims merely recite a "general computing function," such as a "means for storing data."  However, such circumstances are limited, and practitioners would do well to assume that disclosure of the algorithm necessary for carrying out the claimed function is always needed.


Software patent claims are frequently written using functional terms.  That is, the claims recite what the software does, rather than what it is.  Such limitations lack structure for performing the claimed function, and often invoke 35 U.S.C. §112(f) as a result.  Because these limitations are implemented on computers, the specification must describe the algorithm needed to transform a general purpose computer to a special purpose computer programmed to perform the claimed function.  As the court stated in Eon Corp. IP Holdings, LLC v. AT&T Mobility, LLC, "[i]t is well-established that the corresponding structure for a function performed by a software algorithm is the algorithm itself." See Eon, 785 F.3d 616, 621 (Fed. Cir. 2015).  Thus, practitioners should disclose with sufficient detail any algorithms corresponding to computer-implemented claim limitations in the specification, as failing to do so can result in the limitations being deemed indefinite.

The content of this article is intended to provide a general guide to the subject matter. Specialist advice should be sought about your specific circumstances.

To print this article, all you need is to be registered on Mondaq.com.

Click to Login as an existing user or Register so you can print this article.

Similar Articles
Relevancy Powered by MondaqAI
Banner & Witcoff
In association with
Related Topics
Similar Articles
Relevancy Powered by MondaqAI
Banner & Witcoff
Related Articles
Related Video
Up-coming Events Search
Font Size:
Mondaq on Twitter
Register for Access and our Free Biweekly Alert for
This service is completely free. Access 250,000 archived articles from 100+ countries and get a personalised email twice a week covering developments (and yes, our lawyers like to think you’ve read our Disclaimer).
Email Address
Company Name
Confirm Password
Mondaq Topics -- Select your Interests
 Law Performance
 Law Practice
 Media & IT
 Real Estate
 Wealth Mgt
Asia Pacific
European Union
Latin America
Middle East
United States
Worldwide Updates
Registration (you must scroll down to set your data preferences)

Mondaq Ltd requires you to register and provide information that personally identifies you, including your content preferences, for three primary purposes (full details of Mondaq’s use of your personal data can be found in our Privacy and Cookies Notice):

  • To allow you to personalize the Mondaq websites you are visiting to show content ("Content") relevant to your interests.
  • To enable features such as password reminder, news alerts, email a colleague, and linking from Mondaq (and its affiliate sites) to your website.
  • To produce demographic feedback for our content providers ("Contributors") who contribute Content for free for your use.

Mondaq hopes that our registered users will support us in maintaining our free to view business model by consenting to our use of your personal data as described below.

Mondaq has a "free to view" business model. Our services are paid for by Contributors in exchange for Mondaq providing them with access to information about who accesses their content. Once personal data is transferred to our Contributors they become a data controller of this personal data. They use it to measure the response that their articles are receiving, as a form of market research. They may also use it to provide Mondaq users with information about their products and services.

Details of each Contributor to which your personal data will be transferred is clearly stated within the Content that you access. For full details of how this Contributor will use your personal data, you should review the Contributor’s own Privacy Notice.

Please indicate your preference below:

Yes, I am happy to support Mondaq in maintaining its free to view business model by agreeing to allow Mondaq to share my personal data with Contributors whose Content I access
No, I do not want Mondaq to share my personal data with Contributors

Also please let us know whether you are happy to receive communications promoting products and services offered by Mondaq:

Yes, I am happy to received promotional communications from Mondaq
No, please do not send me promotional communications from Mondaq
Terms & Conditions

Mondaq.com (the Website) is owned and managed by Mondaq Ltd (Mondaq). Mondaq grants you a non-exclusive, revocable licence to access the Website and associated services, such as the Mondaq News Alerts (Services), subject to and in consideration of your compliance with the following terms and conditions of use (Terms). Your use of the Website and/or Services constitutes your agreement to the Terms. Mondaq may terminate your use of the Website and Services if you are in breach of these Terms or if Mondaq decides to terminate the licence granted hereunder for any reason whatsoever.

Use of www.mondaq.com

To Use Mondaq.com you must be: eighteen (18) years old or over; legally capable of entering into binding contracts; and not in any way prohibited by the applicable law to enter into these Terms in the jurisdiction which you are currently located.

You may use the Website as an unregistered user, however, you are required to register as a user if you wish to read the full text of the Content or to receive the Services.

You may not modify, publish, transmit, transfer or sell, reproduce, create derivative works from, distribute, perform, link, display, or in any way exploit any of the Content, in whole or in part, except as expressly permitted in these Terms or with the prior written consent of Mondaq. You may not use electronic or other means to extract details or information from the Content. Nor shall you extract information about users or Contributors in order to offer them any services or products.

In your use of the Website and/or Services you shall: comply with all applicable laws, regulations, directives and legislations which apply to your Use of the Website and/or Services in whatever country you are physically located including without limitation any and all consumer law, export control laws and regulations; provide to us true, correct and accurate information and promptly inform us in the event that any information that you have provided to us changes or becomes inaccurate; notify Mondaq immediately of any circumstances where you have reason to believe that any Intellectual Property Rights or any other rights of any third party may have been infringed; co-operate with reasonable security or other checks or requests for information made by Mondaq from time to time; and at all times be fully liable for the breach of any of these Terms by a third party using your login details to access the Website and/or Services

however, you shall not: do anything likely to impair, interfere with or damage or cause harm or distress to any persons, or the network; do anything that will infringe any Intellectual Property Rights or other rights of Mondaq or any third party; or use the Website, Services and/or Content otherwise than in accordance with these Terms; use any trade marks or service marks of Mondaq or the Contributors, or do anything which may be seen to take unfair advantage of the reputation and goodwill of Mondaq or the Contributors, or the Website, Services and/or Content.

Mondaq reserves the right, in its sole discretion, to take any action that it deems necessary and appropriate in the event it considers that there is a breach or threatened breach of the Terms.

Mondaq’s Rights and Obligations

Unless otherwise expressly set out to the contrary, nothing in these Terms shall serve to transfer from Mondaq to you, any Intellectual Property Rights owned by and/or licensed to Mondaq and all rights, title and interest in and to such Intellectual Property Rights will remain exclusively with Mondaq and/or its licensors.

Mondaq shall use its reasonable endeavours to make the Website and Services available to you at all times, but we cannot guarantee an uninterrupted and fault free service.

Mondaq reserves the right to make changes to the services and/or the Website or part thereof, from time to time, and we may add, remove, modify and/or vary any elements of features and functionalities of the Website or the services.

Mondaq also reserves the right from time to time to monitor your Use of the Website and/or services.


The Content is general information only. It is not intended to constitute legal advice or seek to be the complete and comprehensive statement of the law, nor is it intended to address your specific requirements or provide advice on which reliance should be placed. Mondaq and/or its Contributors and other suppliers make no representations about the suitability of the information contained in the Content for any purpose. All Content provided "as is" without warranty of any kind. Mondaq and/or its Contributors and other suppliers hereby exclude and disclaim all representations, warranties or guarantees with regard to the Content, including all implied warranties and conditions of merchantability, fitness for a particular purpose, title and non-infringement. To the maximum extent permitted by law, Mondaq expressly excludes all representations, warranties, obligations, and liabilities arising out of or in connection with all Content. In no event shall Mondaq and/or its respective suppliers be liable for any special, indirect or consequential damages or any damages whatsoever resulting from loss of use, data or profits, whether in an action of contract, negligence or other tortious action, arising out of or in connection with the use of the Content or performance of Mondaq’s Services.


Mondaq may alter or amend these Terms by amending them on the Website. By continuing to Use the Services and/or the Website after such amendment, you will be deemed to have accepted any amendment to these Terms.

These Terms shall be governed by and construed in accordance with the laws of England and Wales and you irrevocably submit to the exclusive jurisdiction of the courts of England and Wales to settle any dispute which may arise out of or in connection with these Terms. If you live outside the United Kingdom, English law shall apply only to the extent that English law shall not deprive you of any legal protection accorded in accordance with the law of the place where you are habitually resident ("Local Law"). In the event English law deprives you of any legal protection which is accorded to you under Local Law, then these terms shall be governed by Local Law and any dispute or claim arising out of or in connection with these Terms shall be subject to the non-exclusive jurisdiction of the courts where you are habitually resident.

You may print and keep a copy of these Terms, which form the entire agreement between you and Mondaq and supersede any other communications or advertising in respect of the Service and/or the Website.

No delay in exercising or non-exercise by you and/or Mondaq of any of its rights under or in connection with these Terms shall operate as a waiver or release of each of your or Mondaq’s right. Rather, any such waiver or release must be specifically granted in writing signed by the party granting it.

If any part of these Terms is held unenforceable, that part shall be enforced to the maximum extent permissible so as to give effect to the intent of the parties, and the Terms shall continue in full force and effect.

Mondaq shall not incur any liability to you on account of any loss or damage resulting from any delay or failure to perform all or any part of these Terms if such delay or failure is caused, in whole or in part, by events, occurrences, or causes beyond the control of Mondaq. Such events, occurrences or causes will include, without limitation, acts of God, strikes, lockouts, server and network failure, riots, acts of war, earthquakes, fire and explosions.

By clicking Register you state you have read and agree to our Terms and Conditions