What Are Function Points?
A function point is a unit of measure for functional size as defined within the IFPUG Functional Size Measurement Method.3 Imagine that you are a tourist in a new land, lost
2Refer to Joe Schofield, The statistically unreliable nature of lines of code, CrossTalk, April, pp. 29–33, 2005.
3Refer to IFPUG, Function Point Counting Practices Manual (CPM), Release 4.3, Part 1, page 6; Part 5, page G-4.
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2Certified Function Point Specialist Examination Guide
and hoping to find directions. You pull up to the curb and ask for assistance. Would you rather hear, “You travel down the road a piece, make a left at Joe Franklin’sstore, drive until you see the big oak tree that fell during the storm of
1972 and make a sharp right” or “You drive 1.2 miles, make a left, drive 4.3 miles, and make a sharp right turn—your destination will be 400 feet on your right”?
Function points are a precise measurementof software size designed to remove the ambiguity from consideration of the software being examined. Instead of the abstract notion of “This will be a big project unless Joe can work on it,” we have a solid estimate of a project’s size. Statementsbecome: “This enhancement is estimatedat 1200 function points,” with a follow-up that possibly includes: “Most of our devel- opers produce 30 function points per month, but Joe has produced 45 function points per month on a consistent basis. He would be a real asset to the team if we need this done as quickly as possible.”
How can function point analysisdeliver these results? The function point method is designed around the concept of measuring a unit of work. Functional size enables the estimate of cost and resources required for software development and maintenance regardless of any nonfunctional constraints.