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VHDL (VHSIC[1] Hardware Description Language) is a hardware description language that is used to describe digital (and mixed-signal) systems such as field programmable gate arrays and integrated circuit.

It is a strongly-typed, concurrent and reactive programming language developed by U.S. Department of Defense in the 1980s.[2] It is standardized under the IEEE Standard 1076.[3]


  • Strong Typing - catches such mistakes as bus precision and type mismatches before you synthesise and test your design;
  • Custom Enumerated Types - define named values makes code more readable and helps catch errors in combination with type checking;
  • Custom Record Types - group signals together, improves code readability.


  • Verboseness - VHDL syntax is very verbose;
  • Strong Typing - strong typing also means you need to convert(cast) between different types even if they are similar (i.e. signed to unsigned).


Free and Open Source:

Further Reading

  • Bryan Mealy, Fabrizio Tappero (February 2012). freerangefactory.org. The no-frills guide to writing powerful VHDL code.


  1. Very High Speed Integrated Circuit
  2. https://en.wikipedia.org/wiki/VHDL#History
  3. http://ieeexplore.ieee.org/servlet/opac?punumber=2589