As an example, a block diagram of a radio isn't expected to demonstrate each and every connection and dial and switch, however, the schematic diagram is. The design of a radio does not show the width of every link from the printed circuit board, but the design diagram will not.
The major cities (functions) are recorded but the minor county roads and city roads aren't. After troubleshooting, this large level map is helpful in narrowing down and isolating where a problem or fault is.
Block diagrams rely upon the principle of the black box in which the contents are hidden from view to avoid being distracted by the details or because the details are not known. We know what happens, we all know what happens, but we can't see how the box does its own work.
In process control, block diagrams are a visual vocabulary for describing actions in a intricate system in which cubes are black boxes which represent mathematical or logical operations which take place in order from left to right and top to base, but not the physical things, such as processors or radiators, that perform these operations. It's possible to create such cube diagrams and implement their functionality with technical programmable logic control (PLC) programming languages. )
In electrical engineering, a layout may often begin as a rather significant level block structure, becoming more and more detailed block diagrams because the design develops, finally ending in block diagrams detailed enough that each individual block can be readily implemented (at which point the block structure can be also a schematic diagram). This is referred to as top down design.  Geometric shapes are frequently used at the diagram to assist interpretation and clarify meaning of the procedure or model. Each engineering discipline has their own meaning for every form. Block diagrams are employed in each discipline of engineering. They're also a valuable source of concept building and educationally beneficial in non-engineering disciplines.
Block diagrams are typically used for higher level, less comprehensive descriptions which are intended to clarify general theories without consideration for the specifics of implementation. Contrast this with the design diagrams and layout diagrams used in electrical technology, which show the implementation details of electric elements and physical construction.
In biology there's a growing use of technology principles, techniques of evaluation and ways of diagramming. There is a correlation between the block diagram and what is called Systems Biology Graphical Notation. Since it is there's use created in systems biology of this cube structure technique harnessed by control engineering in which the latter itself is a program of management theory.
An instance of that is the function block structure, one of five programming languages defined in section 3 of this IEC 61131 (view IEC 61131-3) benchmark that is highly formalized (see proper system), with stringent rules for the diagrams are to be assembled. Directed lines are utilized to connect input factors to block input signal, and block outputs to output variables and inputs of different cubes.
A block diagram is a type of a system where the main parts or works are represented by blocks linked by lines that reveal the connections of the cubes.