AutoCAD used a separate monitor connected directly to an S-100 graphics card.  You&#x27;d enter commands into the AutoCAD command line interface and do the drafting on the graphics monitor.<p>That also explains the way ACAD works.  Had the program been created in the post-terminal age it is likely it would have been a point-and-click application, like, say, SolidWorks.  Instead, they relied on commands such as &quot;line&quot;, &quot;circle&quot;, &quot;pline&quot;, etc. typed into the console.  You could also type the parameters rather than clicking around.<p>ACAD also came with a version of Lisp (AutoLISP) you could use to extend its capabilities.  In general terms the approach was to use AutoLISP to create a DSL that made drafting much easier for your particular application.<p>For example, I had a set of programs that created a DSL I could use to layout circuit boards more efficiently than through raw command drafting.  If I remember correctly, I could type &quot;dip&quot; and my code would ask a series of question to ultimately place a, say, DIP 16 package with certain size pads and holes on the current layer.<p>The degree of automation one could be achieved through AutoLISP was remarkable.