Software Maintenance

We can get an approximate idea about the major costs involved during the Life Cycle of a software from the following graph :

[insert picture here about "the software process"]

As we can see from the graph, it was estimated in 1976 by Boehm that the cost of maintaining software would form a huge chunk of the total cost. In fact, the cost of maintaining software was predicted to be over 60% of the total cost. So, a major area where we could concentrate on, to reduce costs, would be in the devising of efficient maintenance techniques for the software and more importantly develop a software so that it is easy to maintain in the future.

[Note: It may not be advisable to take exact figures from a estimation of costs way back in 1976, but it definitely gives us a good idea about where we could make big savings in the cost of the software.]
 

To help in keeping maintenance costs down it would be helpful if we could determine the different costs involved in maintenance. These costs can be grouped under the following categories [LiSw80] :

• Corrective Maintenance : This is maintenance to correct errors. About 20% of the surveyed resources were devoted to this class of activity.
• Adaptive Maintenance : This maintenance results from external changes to which the system must respond, e.g. changes in the hardware or the operating system. This accounts for about 25%.
• Perfective Maintenance : This represents all other changes to an operational system. As a percentage of the total maintenance effort, user enhancements account for 42%, documentation changes 6% and efficiency improvements 4%. In all, 55% of the maintenance effort is perfective.