Editing Hardware description language (section)

==Motivation==
Due to the exploding complexity of digital electronic circuits since the 1970s (see [[Moore's law]]), circuit designers needed [[digital logic]] descriptions to be performed at a high level without being tied to a specific electronic technology, such as [[Emitter-coupled logic|ECL]], [[Transistor–transistor logic|TTL]] or [[CMOS]]. HDLs were created to implement [[register-transfer level]] abstraction, a model of the data flow and timing of a circuit.<ref>{{cite book|last=Ciletti|first=Michael D.|title=Advanced Digital Design with Verilog HDL|publisher=Prentice Hall|year=2011 |isbn=9780136019282 |edition=2nd}}</ref>

There are two major hardware description languages: [[VHDL]] and [[Verilog]]. There are different types of description in them: "dataflow, behavioral and structural".
Example of dataflow of VHDL:

<syntaxhighlight lang="vhdl">
LIBRARY IEEE;
USE IEEE.STD_LOGIC_1164.ALL;

ENTITY not1 IS
    PORT(
        a : IN  STD_LOGIC;
        b : OUT STD_LOGIC
    );
END not1;

ARCHITECTURE behavioral OF not1 IS
BEGIN
    b <= NOT a;
END behavioral;
</syntaxhighlight>