An example of this is the function block structure, one of five programming languages described in section 3 of the IEC 61131 (see IEC 61131-3) standard that's very formalized (see proper system), with stringent rules for how diagrams must be assembled. Directed lines are utilized to link input factors to block inputs, and block presses to output variables and inputs of other cubes.
In process control, block diagrams are a visual vocabulary for describing actions in a complex system where cubes are black boxes that represent logical or mathematical operations which occur in sequence from left to right and top to bottom, but not the physical entities, like processors or radiators, that execute those operations. It's possible to make such cube diagrams and execute their functionality with specialized programmable logic control (PLC) programming languages.
For example, a block diagram of a wireless isn't expected to demonstrate each and every link and dial and switch, however, the design diagram is. The schematic diagram of a wireless does not demonstrate the width of every connection in the circuit board, however the design diagram does.
Block diagrams rely on the principle of the black box where the contents are concealed from view either to avoid being distracted by the facts or because the details aren't known. We understand what goes in, we all know what happens, but we can not see the way the box does its work.
In electrical engineering, a style will often start as a very higher level block structure, becoming more and more detailed block diagrams as the design develops, eventually finishing in block diagrams comprehensive enough that each individual block is easily executed (at that point the block structure is also a schematic diagram). This is known as top down design.  Geometric shapes are frequently utilised in the diagram to help interpretation and describe meaning of this process or model. The geometric shapes are connected by lines to indicate institution and direction/order of traversal. Each engineering field has their own significance for each shape. Block diagrams are used in each discipline of engineering. They are also a valuable source of concept building and educationally beneficial in non-engineering areas.
To create an analogy to the map which makes world, a block diagram is very similar to a highway map of an whole nation. The major cities (serves ) are recorded but the minor county roads and city streets aren't. After troubleshooting, this high level map is useful in narrowing down and isolating where a problem or error is.
A block diagram is a type of a system in which the principal components or functions are represented by cubes connected by lines which reveal the connections of the blocks.
Block diagrams are typically used for higher degree, less comprehensive descriptions that are meant to clarify general theories without concern for the specifics of execution. Compare this with the design diagrams and layout diagrams used in electrical technology, which show the implementation information of electric elements and physical structure.
In biology there's a growing use of engineering fundamentals, techniques of evaluation and methods of diagramming. There's a similarity between the block diagram and what is called Systems Biology Graphical Notation. As it is there's use created in systems biology of this block structure technique harnessed by control technology where the latter itself is an application of control theory.