It is possible to patent programs for computers which, when run on a computer produce a "technical effect". However, if a program does not produce a technical effect when run on a computer it is unlikely to be patentable. A technical effect is generally an improvement in technology, and needs to be in an area of technology which is patentable.

For instance, an improved program for translating between Japanese and English is not patentable because linguistics is a mental process, not a technical field. On the other hand a program which speeds up image enhancement may be patentable because it produces a technical improvement in a technical area. Other restrictions also apply - the UK Patent Office web site has a practice notice on patenting computer software.

The European Patent Office (EPO) takes a similar approach to the UK Patent Office on patenting software. Their website has a press release about their approach to software and business method patents.

Some other countries, such as the USA, which may be a large potential market for software, have a more liberal approach to software patenting, and often grant patents for software which would be excluded in the UK or EPO.

The UK Patent Office has recently completed a consultation exercise to determine whether or not the law regarding the patentability of computer programs should be changed.