Software patenting – method, tangible media, and system claims

What are some of the differences, when patenting software, between a claim for a method (which a computer, programmed with the software executes) and a claim for a non-transient, tangible medium (or media) having instructions which, when executed by a computer, cause the computer to perform a method? What about system claims, for a system that is configured to execute a method? All of these can be used to claim software, but each has its own scope for what is protected by an issued patent. Tangible medium claims protect against an infringer selling DVDs, CD-ROMs or software downloads with your software. Method claims protect against infringers practicing your method, i.e., running your software, and indirectly protect against infringers selling your software so that others can run your software (this is contributory infringement). System claims protect against infringers setting up a system that runs your software. Whether your claim set has one method claim and two system claims, or two method claims and one tangible media claim and so on, may depend on what you want to protect. Or, there may be other factors such as what type of system the software runs on, that may affect your decision as to how to claim. For example, consumer software would benefit from protection provided by a tangible media claim. On the other hand, software that would usually be bundled into a machine (e.g., as firmware) might be best represented as a system claim. Examples of this include industrial controllers, automotive engine controllers, smart appliances and the like.