A block diagram is a diagram of a system where the principal components or functions are represented by cubes joined by lines that reveal the connections of the blocks.
In process management, block diagrams are a visual vocabulary for describing activities in a intricate system where blocks are black boxes which represent mathematical or logical operations that exist in sequence from left to right and top to base, although not the physical entities, such as processors or radiators, that perform those operations. It is likely to make such block diagrams and implement their performance with specialized programmable logic control (PLC) programming languages. )
For example, a block diagram of a wireless isn't expected to demonstrate each and every connection and dial and switch, but the schematic diagram is. The design of a radio doesn't demonstrate the diameter of each connection in the circuit board, but the layout diagram will not.
In electrical engineering, a design may often begin as a rather high level block diagram, getting more and more detailed block diagrams as the design progresses, finally finishing in block diagrams detailed enough that every individual block is easily executed (at that stage the block diagram is also a schematic diagram). This is referred to as top down layout.  Geometric shapes are often utilised at the diagram to aid interpretation and clarify meaning of this process or model. The geometric shapes are linked by lines to indicate association and direction/order of traversal. Each engineering discipline has their own significance for every shape. Block diagrams are employed in each discipline of technology. They are also a valuable source of concept building and educationally valuable in non-engineering disciplines.
Block diagrams are typically used for higher level, less comprehensive descriptions which are meant to clarify overall concepts without difficulty for the specifics of execution. Compare this with the design diagrams and layout diagrams used in electric engineering, which show the implementation information of electric components and physical structure.
Block diagrams rely upon the principle of this black box where the contents are concealed from view either to avoid being distracted by the facts because the details are not known. We all know what goes in, we know what happens, but we can't see how the box does its work.
An illustration of that is that the function block diagram, among five programming languages defined in part 3 of the IEC 61131 (see IEC 61131-3) benchmark that is quite formalized (see formal method ), with stringent rules to the diagrams are to be built. Directed lines are used to link input factors to block input signal, and block presses to output factors and inputs of different cubes.
To make an analogy to the map creating world, a block diagram is very similar to a highway map of an whole nation. The major towns (functions) are recorded but the minor county roads and city streets aren't. When troubleshooting, this large degree map is helpful in narrowing down and isolating where a issue or fault is.
In biology there's a growing use of technology principles, techniques of analysis and methods of diagramming. There's some similarity between the block structure and what's named Systems Biology Graphical Notation. Since it is there's use created in systems biology of this block diagram technique exploited by controller technology where the latter itself is an application of control theory.