Control flow represents the relationship between actions in a sequence as well as between input and output objects, shown with messages attached to associations or as solid arrows between activity symbols.
In computer science control flow (or alternatively, flow of control) refers to the order in which the individual statements or instructions of an imperative program are performed or executed. Within a programming language, a control flow statement is an instruction that when executed can cause a change in the subsequent control flow to differ from the natural sequential order in which the instructions are listed. Discussion of control flow is almost always restricted to a single thread of execution, as it depends upon a definite sequence in which instructions are executed one at a time.
The conditional and iterative statements that control the behavior of a module. These statements evaluate variables (counters, flags, and tokens) to control the operation of different sections of a behavioral description.