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Software patent does not have a universally accepted definition. One definition, proposed by the Foundation for a Free Information Infrastructure, is that a software patent is a "patent on any performance of a computer realised by means of a computer program." Bessen & Hunt 2004 propose an alternative way of identifying software patents that is more easily used in practice.
A related term is computer-implemented invention (CII), which is used by the European Patent Office (EPO). One EPO definition of a CII is "an invention whose implementation involves the use of a computer, computer network or other programmable apparatus, the invention having one or more features which are realised wholly or partly by means of a computer program."
There is intense debate as to what extent either software patents or patents on computer-implemented inventions should be granted, if at all. Different aspects of this debate include:
The extent to which patents for processes implemented in software should be patentable as a matter of policy; and The inventive step and non-obviousness requirements that should be met for a patent involving software.
The complete, up-to-date and editable article about Software Patent can be found at Wikipedia: Software Patent