AutoCAD
AutoCAD software is primarily used to create 2D drawings and 2D and 3D models, but it also works well for creating animations, and a wide range of graphical, print and video output formats, and can be used in collaboration with other applications such as Microsoft Office.
Versions
There are five distinct AutoCAD versions, as follows:
AutoCAD R16: This was the first desktop version. This had a maximum resolution of 128x16 pixels and was available on the Apple II, Apple III, IBM PC compatibles and a range of other computers. The first version of AutoCAD also had 16 levels of graphics depth, three types of layer, no 2D dimensioning, and a central menu bar. It was first released in 1983.
AutoCAD R20: This is the first version to have AutoCADs internal 3D engine. There were a few minor differences, such as an improved program user interface, the addition of the polygon, and an update to the commands for projection and rotation. The first release of AutoCAD also had 64 levels of graphics depth, two types of layer, and a fully interactive user interface. It was released in 1984.
AutoCAD R32: This is the version with the user interface. AutoCAD R32 was the first version to have a user interface. It also contained the first application program interfaces (APIs) for the Graphical Device Interface (GDI) and the Extended Display. AutoCAD R32 also introduced a new types of dimensioning and text which allowed text and dimensioning to be associated with one or more layers, and a command for text placement. This version was the first to use floating windows, which work as mini toolbars, containing many of the most commonly used commands. AutoCAD R32 has an internal 64-bit floating point number processor, which allowed for three-dimensional objects to be displayed in full 3D. AutoCAD R32 was released in 1985.
AutoCAD R48: This version was the first to be fully interactive and to have an up-to-date graphics engine. There are many changes that were made in this version, such as 3D text, full 3D dimensioning, unlimited z-axis, and the ability to associate all layers with a text or dimension block. AutoCAD R48 also introduced the interface to other software packages, and the first version to
AutoCAD
Language constructs 
AutoCAD supports a large number of programming languages for software development, including AutoLISP, Visual LISP, VBA, C++ and JavaScript.
AutoCAD uses the Visual LISP programming language as the programming language for its CAD automation products, including AutoCAD, Autodesk Alias, Autodesk Architecture, Autodesk Civil 3D, Autodesk Electrical, Autodesk Mechanical, Autodesk Inventor, Autodesk Project Builder, Autodesk Revit, Autodesk RVT, Autodesk 3ds Max, and Autodesk Softimage, with releases as late as 2015 for 3ds Max.
AutoCAD also uses Visual LISP in Autodesk Forge and Autodesk Components for DWF and DXF.
AutoCAD's SQL Server Connector is based on Visual LISP and allows programming SQL Server databases with Visual LISP. AutoCAD SQL Server (R) is a programming language independent of AutoCAD. Its syntax is SQL-92 and can be used with other languages as well.
AutoLISP 
AutoLISP is a platform independent, Open Source visual programming language for AutoCAD, and is the language for AutoCAD's CAD automation products, including AutoCAD, Autodesk Alias, Autodesk Architecture, Autodesk Civil 3D, Autodesk Electrical, Autodesk Mechanical, Autodesk Inventor, Autodesk Project Builder, Autodesk Revit, Autodesk RVT, Autodesk 3ds Max, and Autodesk Softimage, with releases as late as 2015 for 3ds Max.
AutoCAD's SQL Server Connector is based on AutoLISP.
AutoLISP supports an object-oriented programming framework and a visual graphics toolkit. It supports both procedural and object-oriented programming styles. In AutoLISP, the major programming style is object-oriented, so the concept of an array of "objects" is implemented.
An array of objects is represented in AutoLISP as a list of command objects. Each command object contains information about the attributes of the command, and the list of command objects, in the array, contains information about all of the attributes of the commands in the array. For example, a command that performs a straight-line drawing could be represented by the following code:
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