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+.. _INT:Overview:
+
+Overview
+########
+
+.. figure:: ../_static/internals.png
+   :width: 100%
+   :align: center
+
+   Architecture overview of the GHDL toolkit (CLI, libghdl, pyGHDL and ghdl-yosys-plugin).
+
+`GHDL` is architectured like a traditionnal compiler. It has:
+
+* a driver (sources in :ghdlsrc:`src/ghdldrv <ghdldrv>`) to call the programs (compiler, assembler, linker) if needed.
+
+* a runtime library named GRT (sources in :ghdlsrc:`src/grt <grt>`) to help execution at run-time.
+  This ensures that execution is cycle-accurate.
+
+* a front-end (sources in :ghdlsrc:`src/vhdl <vhdl>`) to parse and analyse VHDL.
+  See :ref:`INT:Frontend` and :ref:`INT:AST`.
+
+* multiple back-ends to generate either code or netlists.
+
+  * Three for :ref:`simulation <USING:Simulation>` (sources are in :ghdlsrc:`src/ortho <ortho>`): mcode, LLVM and GCC.
+    See :ref:`BUILD`.
+  * Two for :ref:`synthesis <USING:Synthesis>` (sources in :ghdlsrc:`src/synth <synth>`):
+    :ref:`--synth <Synth:command>` and :ref:`Synth:plugin`.
+
+The architecture is modular and some of the components are available through the shared library ``libghdl``.
+``libghdl`` is used by the :ref:`Synth:plugin`, the Language Server Protocol (LSP) server, and to fill the data of
+pyVHDLModel (see :doc:`vhdlmodel:index`).
+
+The main work with regard to understanding the VHDL language is performed by the front-end, which is documented in the
+next section.