A Brief History of VHDL

           VHDL which stands for Very High Speed Integrated Circuit(VHSIC) Hardware Description Language was develpoed in early 1980s under the VHSIC program.In this program,a number of high tech companies were involved in making VHSIC chips for U.S Department of Defense(DoD).At that time,each company used its own primitive Hardware Description Language.Moreover these company based languages provided the researchers with only gate level design tools.They did not support large scale design and also prevented these companies from unifying their efforts in developing VHSIC chips.So the need for standardized,extensive hardware description language was generated.
             To meet this need a research team of IBM,Intermetrics and Texas Instruments were assembled by DoD and instructed to develop a standard for powerful hardware description language based tools.The team produced VHDL Version 7.2 in 1985.The standardization however could not satisfy the design requirements for wide variety of companies.In 1986,IEEE was tasked with globally standardizing the language,the result was IEEE standard 1076-1987 version of VHDL,which was also recognised by American National Standards Institute.
                In 1993,VHDL was updated and more features were added resulting in IEEE standard 1076-1993.One of the major enhancement was addition of several packages that added different features.One of the packages std_logic_1164 added seven additional logic levels to logic 0 and logic 1.