Information Flow Metric

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.

FAN IN (A) Return values scanf()

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

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

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.

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.