What is preventive software maintenance?

Approaches software maintenance from the service point of view. I particularly emphasize co-operation with the client. My definition of software maintenance is that software maintenance refers to all the actions that are needed to keep software in such a running order that it achieves all its objectives from the beginning until the end of its usage. The ideas I present are based on several software maintenance development projects that I have been involved in as a consultant. I answer the title question by describing 'preventive software maintenance' in connection with classification factors.