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ChaPter 1 • SyStemS, roleS, and develoPment methodologieS 9

Figure 1.2
Some researchers estimate that the
amount of time spent on system
New Systems and
Other Activities maintenance may be as much as
40% 60 percent of the total time spent
Maintenance of on systems projects.
Existing Systems
60%

The Impact of Maintenance
After the system is installed, it must be maintained, meaning that the computer programs must be
modified and kept up to date. Figure 1.2 illustrates the average amount of time spent on mainte-
nance at a typical MIS installation. Estimates of the time spent by departments on maintenance
have ranged from 48 to 60 percent of the total time spent developing systems. Very little time
remains for new systems development. As the number of programs written increases, so does the
amount of maintenance they require.
Maintenance is performed for two reasons. The first of these is to correct software errors.
No matter how thoroughly a system is tested, bugs or errors creep into computer programs. Bugs
in commercial PC software are often documented as “known anomalies,” and they are corrected
when new versions of the software are released or in an interim release. In custom software (also
called bespoke software), bugs must be corrected as they are detected.
The other reason for performing system maintenance is to enhance the software’s capabili-
ties in response to changing organizational needs, generally involving one of the following three
situations:

1. Users often request additional features after they become familiar with the computer system
and its capabilities.
2. The business changes over time.
3. Hardware and software are changing at an accelerated pace.
Figure 1.3 illustrates the amount of resources—usually time and money—spent on systems
development and maintenance. The area under the curve represents the total dollar amount
spent. You can see that over time, the total cost of maintenance is likely to exceed that of sys-
tems development. At a certain point it becomes more feasible to perform a new systems study
because the cost of continued maintenance is clearly greater than the cost of creating an entirely
new information system.

Major Changes Figure 1.3
in Both Business
and Technology Resource consumption over the
system life.
Postinstallation Minor Changes
Bugs Due to Bugs and
Enhancements
Systems
Amount of Development
Resources Time
Consumed,
Time and
Money

Installation
Day