It is widely used to measure the size of software. Function Point concentrates on functionality provided by the system. Features and functionality of the system are used to measure the software complexity.
Function point counts on five parameters, named as External Input, External Output, Logical Internal Files, External Interface Files, and External Inquiry. To consider the complexity of software each parameter is further categorized as simple, average or complex.
Let us see parameters of function point:
Every unique input to the system, from outside, is considered as external input. Uniqueness of input is measured, as no two inputs should have same formats. These inputs can either be data or control parameters.
● Simple – if input count is low and affects less internal files
● Complex – if input count is high and affects more internal files
● Average – in-between simple and complex.
All output types provided by the system are counted in this category. Output is considered unique if their output format and/or processing are unique.
● Simple – if output count is low
● Complex – if output count is high
● Average – in between simple and complex.