Function Point Analysis in Software Engineering - Step-by-Step Execution

Concept Flow - Function Point Analysis

Identify Functions

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Classify Functions

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Assign Complexity Weights

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Calculate Unadjusted Function Points

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Determine Value Adjustment Factors

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Calculate Adjusted Function Points

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Use FP for Estimation and Planning

The process starts by identifying and classifying software functions, assigning weights, calculating unadjusted points, adjusting for complexity, and finally using the result for project estimation.

Execution Sample

Software Engineering

Identify functions: EI=3, EO=2, ILF=4
Assign weights: EI=4, EO=5, ILF=10
Calculate UFP = (3*4)+(2*5)+(4*10)
Value Adjustment Factor (VAF) = 1.1
Adjusted FP = UFP * VAF

This example calculates function points by counting function types, applying weights, summing for unadjusted points, then adjusting by a factor.

Analysis Table

Step	Action	Calculation	Result
1	Count External Inputs (EI)	EI = 3	3
2	Count External Outputs (EO)	EO = 2	2
3	Count Internal Logical Files (ILF)	ILF = 4	4
4	Assign weights	EI=4, EO=5, ILF=10	Weights set
5	Calculate Unadjusted Function Points (UFP)	(3*4)+(2*5)+(4*10)	12 + 10 + 40 = 62
6	Determine Value Adjustment Factor (VAF)	VAF = 1.1	1.1
7	Calculate Adjusted Function Points	62 * 1.1	68.2

💡 Calculation ends after adjusted function points are computed for estimation.

State Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	After Step 5	After Step 7
EI	0	3	3	3	3	3
EO	0	0	2	2	2	2
ILF	0	0	0	4	4	4
Weights	None	None	None	None	EI=4, EO=5, ILF=10	EI=4, EO=5, ILF=10
UFP	0	0	0	0	62	62
VAF	1	1	1	1	1	1.1
Adjusted FP	0	0	0	0	0	68.2

Key Insights - 3 Insights

Why do we multiply counts by weights instead of just summing counts?

Weights reflect the complexity or effort of each function type, so multiplying counts by weights (see Step 5 in execution_table) gives a more accurate size measure than just counting.

What is the purpose of the Value Adjustment Factor (VAF)?

VAF adjusts the unadjusted function points to account for general system characteristics like performance or usability (see Step 6 and 7). It fine-tunes the estimate beyond raw counts.

Can function points be fractional like 68.2?

Yes, because the VAF is a decimal multiplier, adjusted function points can be fractional, representing a more precise size estimate (see Step 7).

Visual Quiz - 3 Questions

Look at the execution_table at Step 5, what is the Unadjusted Function Points (UFP) value?

A 62

B 68.2

C 12

D 40

💡 Hint

Check the 'Result' column at Step 5 in the execution_table.

At which step is the Value Adjustment Factor (VAF) applied?

A Step 4

B Step 7

C Step 6

D Step 3

💡 Hint

Look for the step where UFP is multiplied by VAF in the execution_table.

If the number of External Inputs (EI) increased from 3 to 5, how would the UFP change at Step 5?

A Increase by 10

B Increase by 20

C Increase by 8

D No change

💡 Hint

Each EI has weight 4, so extra 2 EIs add 2*4=8 to UFP (see Step 5 calculation).

Concept Snapshot

Function Point Analysis (FPA) measures software size by counting functions.
Steps: Identify functions → Classify types → Assign complexity weights → Calculate Unadjusted FP → Adjust with Value Adjustment Factor → Use for estimation.
Weights reflect effort; VAF adjusts for system characteristics.
Result is a numeric size estimate to help plan and estimate projects.

Full Transcript

Function Point Analysis is a method to measure software size by counting and weighting different types of functions like inputs, outputs, and files. The process starts by identifying these functions and classifying them. Each function type is assigned a weight based on complexity. Multiplying counts by weights gives the Unadjusted Function Points (UFP). Then, a Value Adjustment Factor (VAF) is determined to adjust for general system characteristics such as performance or usability. Multiplying UFP by VAF gives the Adjusted Function Points, which provide a more accurate size estimate. This estimate helps in project planning and effort estimation. For example, if there are 3 external inputs with weight 4, 2 external outputs with weight 5, and 4 internal logical files with weight 10, the UFP is calculated as (3*4)+(2*5)+(4*10) = 62. Applying a VAF of 1.1 results in 68.2 adjusted function points. This method helps teams understand software size in a standardized way.