Strongly connected region

Strongly connected region --- зона, сильно связная область.

A nontrivial strongly connected subgraph of a cf-graph is called a strongly connected region (or zone).

A zone with a single entry node is called single-entry.

A zone is called multientry, if it has no less than two entry nodes. A multientry zone [math]\displaystyle{ S }[/math] is maximal, if there is no such multientry zone [math]\displaystyle{ Z }[/math] that [math]\displaystyle{ S }[/math] is a proper subfragment of [math]\displaystyle{ Z }[/math].

The following properties of maximal multientry zones hold. Maximal multientry zones are not pairwise intersected. A node [math]\displaystyle{ p }[/math] is an initial node of maximal multientry zone [math]\displaystyle{ S }[/math] iff [math]\displaystyle{ p }[/math] is an entry node of [math]\displaystyle{ S }[/math].