Functional block diagram

A functional block diagram is a block diagram, used in systems engineering and software engineering, that describes the functions of a system and how they relate to one another. Each function is drawn as a block, the inputs and outputs of a block are drawn as lines, and the diagram shows the relationships between functions and the functional sequences and paths followed by matter or signals. Additional schematic symbols can be added to show particular properties. Functional block diagrams have been used since the late 1950s, in applications from systems engineering to software engineering, and became a necessity in complex systems design as a way to understand the present system and the relationship of each part to the whole. Many specific types have emerged. The functional flow block diagram combines the functional block diagram with the flowchart, and many software development methodologies are built on particular functional block diagram techniques. In industrial computing, the Function Block Diagram is a graphical language for developing software applications for programmable logic controllers.