1. Information Flow Metric

2. Two concepts are common to all information flow metrics:
Several metrics have been developed to measure information flow complexity.
Two concepts are common to all information flow metrics:
Fan-in: is the information that flows into a procedure.
Fan-out: is what comes out of it.

4. FAN IN (A)
Return values
scanf()

5. FAN OUT (A) Return values Number of arguments passed in calling
prinf()

6. Information Flow (IF)
weighted IFC = length * (fanin * fanout)2

7. Example
Consider the following graph. (module (file, procedure or node) as node and call between them as edges)
Fan-in of a module is the number of other modules calling to this module directly.
Fan-out of a module is the number of other modules immediately called by this module.

8. Module A has
Fan-in = 3 and fan-out = 2
High fan-in shows better design structure. Higher fan-in means this module has been used heavily, this shows re-usability of module and thus reduces redundancy in coding.
Fan-out indicate coupling between modules. High fan out means highly coupled module. High fan-out indicates module depends highly on other module and thus shows poor design structure.
High fan-out also increases maintainability cost. Any changes in module require seeing other modules.