for visualizing and teaching geometry, and for producing mathematical illustrations. In GCLC, figures are described rather than drawn. This approach stresses the fact that geometrical constructions are abstract, formal procedures and not figures. A concrete figure can be generated on the basis of the abstract description. There are several output formats, including LaTeX, LaTeX/PStricks, LaTeX/Tikz, SVG and PostScript. There is a built-in geometry theorem prover (based on the area method). GCLC is available for Windows and Linux. WinGCLC is a Windows version of GCLC with a graphical interface that provides a range of additional functionalities. GCLC is open source software (licence CC BY-ND). GeoGebra GeoGebra is software that combines geometry, algebra and calculus for mathematics education in schools and universities. It is available free of charge for non-commercial users. License: open source under GPL license (free of charge) Languages: 55 Geometry: points, lines, all conic sections, vectors, parametric curves, locus lines Algebra: direct input of inequalities, implicit polynomials, linear and quadratic equations; calculations with numbers, points and vectors Calculus: direct input of functions (including piecewise-defined); intersections and roots of functions; symbolic derivatives and integrals (built-in CAS); sliders as parameters Parametric Graphs: Yes Implicit Polynomials: Yes Web Export: all constructions exportable as web pages as a Java applet Macros: usable both as tools with the mouse and as commands in the input field Animation: Yes Spreadsheet: Yes, the cells can contain any GeoGebra object (numbers, points, functions etc.) Dynamic text: Yes (including LaTeX) Platforms: Mac OS, Unix/Linux, Windows (any platform that supports Java 1.5 or later) Continuity: uses a heuristic 'near-to-approach' to avoid jumping objects GeoKone.NET GeoKone.NET is an interactive recursive natural geometry (or "sacred geometry") generator that runs in a web browser. GeoKone allows the user to create geometric figures using naturalistic rules of recursive copying, such as the Golden ratio. Geolog Geolog is a logic programming language for finitary geometric logic. Geometry Expressions Geometry Expressions Does symbolic geometry. It uses real symbolic inputs and returns real and symbolic outputs. It emphasises use with a Computer Algebra System (CAS), as well as exporting and sharing via interactive HTML5, Lua, and OS X dashboard widget apps. The Geometer's Sketchpad The Geometer's Sketchpad (GSP) Deterministic Languages: English, Spanish, Danish, Russian, Korean, Thai, Traditional and Simplified Chinese, French, Lithuanian (current version); others (older versions) Macros: Yes ("custom tools" and "scripts") Java-applet: Yes Animation: Yes Locus: Yes, including point on locus Assignments: No Measurement/Calculations: