Control flow diagram
Control flow diagrams were developed in the 1950s, and are widely used in multiple engineering disciplines. They are one of the classic business process modeling methodologies, along with flow charts, data flow diagrams, functional flow block diagram, Gantt charts, PERT diagrams, and IDEF.
A control flow diagram can consist of a subdivision to show sequential steps, with if-then-else conditions, repetition, and/or case conditions. Suitably annotated geometrical figures are used to represent operations, data, or equipment, and arrows are used to indicate the sequential flow from one to another.
There are several types of control flow diagrams, for example:
- Change control flow diagram, used in project management
- Configuration decision control flow diagram, used in configuration management
- Process control flow diagram, used in process management
- Quality control flow diagram, used in quality control.
In software and systems development control flow diagrams can be used in control flow analysis, data flow analysis, algorithm analysis, and simulation. Control and are most applicable for real time and data driven systems. These flow analyses transform logic and data requirements text into graphic flows which are easier to analyze than the text. PERT, state transition, and transaction diagrams are examples of control flow diagrams.
Types of Control Flow Diagrams 
Process Control Flow Diagram 
A flow diagram can be developed for the process control system for each critical activity. Process control is normally a closed cycle in which a sensor provides information to a process control software application through a communications system. The application determines if the sensor information is within the predetermined (or calculated) data parameters and constraints. The results of this comparison are fed to an actuator, which controls the critical component. This feedback may control the component electronically or may indicate the need for a manual action.
This closed-cycle process has many checks and balances to ensure that it stays safe. The investigation of how the process control can be subverted is likely to be extensive because all or part of the process control may be oral instructions to an individual monitoring the process. It may be fully computer controlled and automated, or it may be a hybrid in which only the sensor is automated and the action requires manual intervention. Further, some process control systems may use prior generations of hardware and software, while others are state of the art.
Performance seeking control flow diagram 
The figure presents an example of a performance seeking control flow diagram of the algorithm. The control law consists of estimation, modeling, and optimization processes. In the Kalman filter estimator, the inputs, outputs, and residuals were recorded. At the compact propulsion system modeling stage, all the estimated inlet and engine parameters were recorded.
In addition to temperatures, pressures, and control positions, such estimated parameters as stall margins, thrust, and drag components were recorded. In the optimization phase, the operating condition constraints, optimal solution, and linear programming health status condition codes were recorded. Finally, the actual commands that were sent to the engine through the DEEC were recorded.
See also 
- Glenn B. Gilyard and John S. Orme (1992) Subsonic Flight Test Evaluationof a Performance Seeking ControlAlgorithm on an F-15 Airplane NASA Technical Memorandum 4400.
- Thomas Dufresne & James Martin (2003). "Process Modeling for E-Business". INFS 770 Methods for Information Systems Engineering: Knowledge Management and E-Business. Spring 2003
- FDA glossary of terminology applicable to software development and computerized systems. Accessed 14 Jan 2008.
- Dolores R. Wallace et al. (1996). Reference Information for the Software Verification and Validation Process, NIST Special Publication 500-234.
- National Institute of Justice (2002). A Method to Assess the Vulnerability of U.S. Chemical Facilities. Series: Special Report.