The Function Block Diagram (FBD) is a graphical language for programmable logic controller design, which can describe the function input variables and output variables. As shown in the below image template, a main function in the block diagram is described as a set of elementary blocks. At the same time, the inputs and outputs of the blocks are wired together with connection lines or links. As per the image, the main functions are represented by blocks connected by lines that show the relationships of the blocks. Instead of creating the main function block diagrams from scratch, use EdrawMax pre-defined templates as it provides the right facts and figures that ease the entire process.