Levels of abstraction: Behavioral, Structural and Physical

VHDL (VHSIC Hardware Description Language) is a hardware description language used in electronic design automation to describe digital and mixed-signal systems such as field-programmable gate arrays and integrated circuits. VHSIC is an abbreviation for Very High Speed Integrated Circuit. It can describe the behaviour, − structure, and − timing of a logic circuit., but is particularly suited as a language to describe the structure and behaviour of digital electronic hardware designs, such as ASICs and FPGAs as well as conventional digital circuits. VHDL is commonly used to write text models that describe a logic circuit. Such a model is processed by a synthesis program, only if it is part of the logic design. A simulation program is used to test the logic design using simulation models to represent the logic circuits that interface to the design. This collection of simulation models is commonly called a testbench.The highest level of abstraction is the behavioral level that describes a system in terms of what it does (or how it behaves) rather than in terms of its components and interconnection between them,The structural level, on the other hand, describes a system as a collection of gates and components that are interconnected to perform a desired function