Using function points to measure and estimate real-time and embedded software: Experiences and guidelines

The developers of real-time and embedded software face - just like the developers of other types of software - the problem of estimating the cost of development. To this end, the most widely used methods and tools require that the functional size of the program to be developed is measured. However, the functional size measurement methods available - namely, Function Point Analysis and its evolutions - are traditionally considered not well suited for representing the functionality of real-time and embedded software. Actually, the problem is that the definition of Function Points and their counting rules make reference almost exclusively to traditional "business" software. In this paper, the problem of applying FPA to embedded and real-time software is tackled. A set of hints and examples - derived from industrial experience - are given, supporting the application of standard function point counting to real-time and embedded software. It is then shown that the obtained measures successfully supported the estimation of a set of programs in the avionics domain.