+<div id="outline-container-sec-2-1" class="outline-3">
+<h3 id="sec-2-1"><a id="ID-c19c5a3b-dfb0-4f7f-961c-a387b925669f" name="ID-c19c5a3b-dfb0-4f7f-961c-a387b925669f"></a><span class="section-number-3">2.1</span> Extensible, programmable computing environment examples</h3>
+<div class="outline-text-3" id="text-2-1">
+<ul class="org-ul">
+<li><a href="https://www.johndcook.com/blog/2008/04/27/one-program-to-rule-them-all/">GNU Emacs</a> - At the heart, Emacs is text editor on top of Lisp
+runtime. Data storage and computation can be done in <a href="https://www.defmacro.org/ramblings/lisp.html">Lisp</a>. Domain
+specific languages to fit particular problem could be developed as
+needed and Emacs extended to support those languages. Emacs provides
+text buffers that can be used to build user interfaces.