• N - the set of nodes, a node may be empty or contain several statements. A variable v has a definition (def) in node n if n contains a statement in which v is assigned a value. A variable v has a computational use (c-use) in node n if n contains a statement in which v's value is fetched for computational purposes: calculation or output.
• E - the set of edges, an edge may be empty or associated with a Boolean expression corresponding to an outcome of a decision controlling a conditional or a repetitive statement. A variable v has a predicate use (p-use) on edge e if it occurs in the Boolean expression associated with e.

Flow graph example

	PROGRAM main(INPUT,OUTPUT);
	VAR x,y,z: INTEGER;
	BEGIN
	  READLN(x,y,z);
	  y := f1(x,y);
	  WHILE (x >= 0)
	    z := f2(x,y,z);
	    IF (y <= 400) OR (y > x) THEN
	      y := f3(y)
	    ELSE
	      x := f4(x)
	  END;
	  WRITELN(z)
	END.

	A Pascal source code

Labeled with statements and expressions	Labeled with defs, c-uses and p-uses
Flow graph example

Flow Graph Generator (FGG) extracts the information from a procedural programming source code to generate a flow graph ASCII file, which is called flow file [4] in short. So far, FGG works only with the Pascal source code using the programming unit Pasflow [4]. Future development will expand the input domain to cover the specifications given as an Estelle module or an SDL process.

Web
Designed by: T. Nguyen
Updated: May 1997