Custom security or logging processors are good examples where a processor might prove useful. Off the shelf processors even exist like NetCloak 2.5. Filters process incoming requests. SSI process outgoing reply pages.
Processors apply at database level.
Processors may be chained. Chain determined by selection order. Characters from 128 to 255 are defined differently for different operating systems, different languages, and different countries. Because of these differences, computers may encode values differently so they will not translate correctly without help. But because this table will not work for all countries, you can and should modify this table for your specific translation needs.