The first step in the function point counting process is to determine the type of function point count to be conducted. The three possible types of function point counts that we listed earlier are described here.
Development project function point counts measure the functionality provided to end users with the first installation of the application. They include the functionality that will be counted in the initial application function point count, as well as any functionality required for data conversion. If we were replacing the Location application discussed in the previous section with a newly developed application, we would count the functionality provided by the new application. We also must count any conversion functionality required by the users to convert data that resided in the old data files to the new data files. A development project function point count must often be updated as the development proceeds. These subsequent counts would not start from scratch, but they would validate previously identified functionality and attempt to capture added functionality, commonly known as scope creep.
Enhancement project function point counts measure modifications to existing applications and include the combined functionality provided to users by adding new functions, deleting old functions, and changing existing functions. Conversion functionality could also exist in an enhancement project. After an enhancement, the application function point count must be revised to reflect the appropriate changes in the application's functionality.
Application function point counts measure an installed application. They are also referred to as baseline or installed counts, and they size the current functionality provided to end users by the application. An activity's total installed application function point count represents the sum of the application counts for all installed applications currently being utilized and maintained.
In our example, we are counting an existing application without regard to its history of development; therefore, the count is an application count.