Function Point (FP) is a method for estimating software that measures how useful a software system is from the user’s point of view. It is a metric used to determine the size and complexity of a software project by evaluating the number of inputs, outputs, inquiries, internal files, and external interfaces within the system.
In order to figure out how many function points a software system has, you have to figure out how many different kinds of functions it has and count them. Each functionality is classified into one of the following categories:
External Inputs (EI): These are user inputs that process data within the system, such as entering data into a form.
External Outputs (EO): These are the results of the system processing data, like putting a report on the screen.
External Inquiries (EQ): These are user requests for information from the system, such as a search function.
Internal Logical Files (ILF): These are persistent data files maintained within the system.
External Interface Files (EIF): These are files that are sent between the system and other systems.
Once these functionalities have been identified and counted, they are assigned a complexity rating based on the level of effort required to develop them. The complexity rating is based on three things: how complicated the data is, how complicated the processing is, and how complicated the external interface is.
The number of function points is found by multiplying the number of each function by how hard it is to do. Then, the results for all five categories are added together. The number of function points gives an idea of how big and complicated the software system is, which can be used to estimate how long it will take to build, how much it will cost, and what resources will be needed.
Usage
It is used in project planning and estimating cost / effort / time
