Interactive geometry software (IGS) or dynamic geometry environments (DGEs) are computer programs which allow one to create and then manipulate geometric constructions, primarily in plane geometry. In most IGS, one starts construction by putting a few points and using them to define new objects such as lines, circles or other points. After some construction is done, one can move the points one started with and see how the construction changes. History The earliest IGS was the Geometric Supposer, which was developed in the early 1980s. This was soon followed by Cabri in 1986 and The Geometer's Sketchpad. Comparison There are three main types of computer environments for studying school geometry: supposers, dynamic geometry environments (DGEs) and Logo-based programs. Most are DGEs: software that allows the user to manipulate ("drag") the geometric object into different shapes or positions. The main example of a supposer is the Geometric Supposer, which does not have draggable objects, but allows students to study pre-defined shapes. Nearly all of the following programs are DGEs. For a related, comparative physical example of these algorithms, see Lenart Sphere. License and platform The following table provides a first comparison of the different software according to their license and platform. 3D Software General features The following table provides a more detailed comparison : Macros Features related to macro constructions: (TODO) Loci Loci features related to IGS: (TODO) Proof We detail here the proof related features. (TODO) Measurements and calculation Measurement and calculation features related to IGS: (TODO) Graphics export formats Object attributes 2D programs C.a.R. C.a.R. is a free GPL analog of The Geometer's Sketchpad (GSP), written in Java. Cabri Cabri Cabri was developed by the French school of mathematics education in Grenoble (Laborde, 1993) CaRMetal CaRMetal is a free GPL software written in Java. Derived from C.a.R., it provides a different user interface. Cinderella Cinderella, written in Java, is very different from The Geometer's Sketchpad. The later version Cinderella.2 also includes a physics simulation engine and a scripting language. Also, it now supports macros, line segments, calculations, arbitrary functions, plots, etc. Full documentation is available online. Dr Genius Dr Genius was an attempt to merge Dr. Geo and the Genius calculator. Dr. Geo Dr. Geo is a GPL interactive software intended for younger students (7-15). The later version, Dr. Geo II, is a complete rewrite of Dr. Geo, for the Squeak/Smalltalk environment. GCLC GCLC is a dynamic geometry tool