Control Flow as Graph — 1. Sequence

Control Flow as Graph is a sequence consisting of the following 5 notional machines:
1. Sequence
2. Selection
3. Multi-Way Selection
4. Short-Circuit
5. Repetition

Programming Language

imperative / Java



Attribution — Origin / Source

Collected by Matthias Hauswirth — Compilers (control-flow graphs) and flow charts

Conceptual Advantage

See a method as a sequence of statements to execute, and make clear that that sequence starts when the method is called and ends when the method returns.


statement rectangular node
control-flow between statements arrow from node to node
method entry round 'e' node at top
method exit round 'x' node at bottom

Draws Attention To

The idea of a 'sequence' in structured programming, where a sequence consists of statements to execute.

Use When

When introducing how to implement a method's body


Introduction of a potentially new abstract representation (graph with edges and nodes). Entry and exit nodes, which do not correspond to statements in the source code (note: exit comes AFTER a possible return statement).


This is the first in a sequence of "Control Flow as Graph" notional machines:

  1. Sequence
  2. Selection
  3. Multi-Way Selection
  4. Short-Circuit
  5. Repetition

The following video Matthias Hauswirth uses the "Control Flow as Graph" notional machine in his "Programming Fundamentals 2" Bachelor course to explain sequences of statements as well as the entry and exit node in Java. It also discusses if-statements (covered in the Selection variant of this notional machine).

More Information

This notional machine is implemented by the Informa Clicker tool. This tool allows students in a classroom to construct control flow graphs in in-class clicker exercises.

Check this research paper

Matthias Hauswirth and Andrea Adamoli
Solve & Evaluate with Informa: A Java-based Classroom Response System for Teaching Java
PPPJ '09

Comments or Feedback?

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