2. S/W Maintenance
Any work done to change the s/w after it is in operation is considered to be maintenance work.
It is a broader activity which includes error correction, enhancements of capabilities, Deletion of obsolete capabilities and optimization.

3. Categories/Types of Maintenance
Corrective Maintenance: It refers to modification initiated by defects in the s/w.
Error occur when changes made to the s/w are incorrect, incomplete, wrongly communicated or change request is misunderstood.
Adaptive Maintenance: Modifying the s/w to match changes in the ever changing environment. For eg business policy, gov policies, work patterns, s/w or h/w operating plateforms.

4. Perfective Maintenance: Improving processing efficiency or performance.
Preventive maintenance: There are long term effects of corrective, adaptive and perfective changes. This tends to cause in the complexity of the s/w, which reflect deteriorating structure. The work is required to be reduce it. This work may be named as Preventive maintenance.