Software Engineering

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11.2 
Behavioral analysis
11.2.3 
Identify data flows
The purpose of most software functions is to transform inputs into an output or 
product. However, some functions will receive control flow instead of an input. 
Examples of functions that receive only control flow include: (1) the action to pre-
sent graphical user informational screens, messages, or dialog screens; (2) take 
action on global data values; and (3) take action when a state variable (e.g., com-
puting environment health indication or software procedural status) has changed 
or needs to be assessed (e.g., obtain the status of the default printer). While func-
tions that do not directly process data may not satisfy computer language specific or 
mathematical criteria, they do perform significant actions within the software engi-
neering field of study.
Data items represent the information that flows among functions. The pass-
ing of data between software functions represents a functional interface, such as a 
subroutine invocation or “call” statement. The controlling function passes a vari-
able to another function that is processed and the result returned to the controlling 
function. For example, a function may invoke a temperature conversion function 
by passing a temperature value in Fahrenheit. The receiving function converts 
the Fahrenheit temperature value to Celsius and returns the resulting value to the 
FIGURE 11.2
Example of an FFBD.

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