A block diagram is a shorthand, pictorial representation of the cause and effect relationship between the input and output of a system, It provides a convenient and useful
method for characterizing the functional relationships among the various COmponents of a system. Block diagrams are representations of either (a) the schematic diagram of a physical system or (b) the set of mathematical equations characterizing its parts. The simplest form of the block diagram is the single block, with one input and one output (Fig. 2.4). The interior of the rectangle representing the block usually contains (a) the name of the component, (b) a description of the component, or (c) the symbol for the mathematical operation to be performed on the input to yield the output. The arrows represent the direction of unilateral information or signal flow. The standard symbols used to represent various types of blocks are shown in Fig. 25.