In software languages, a function block contains input
variables, output variables, through variables, internal variables, and an
internal behavior description of the function block. Function blocks are used
primarily to specify the properties of a user function. Many software languages
are based on function blocks. Function block is abbreviated as FB.
Function Block Programming (PDF) Function Block Diagrams (FBDs) are another part of the IEC 61131-3 standard. The primary concept behind a FBD is data flow.
Function Blocks In engineering disciplines, especially within time driven systems, software languages are often based on function blocks. By Torsten Heverhagen, Robert Hirschfeld, Rudolf Tracht.