I am happy that, twenty five years after the very first versions of GCLC and with many related tools that appeared in the meanwhile, there is still a steady and wide need for the tool GCLC. With thousands of GCLC users worldwide, with many books, journal articles, and theses illustrated with the help of GCLC, and with many courses on different levels that are taught using GCLC, I am encouraged to keep the project GCLC active. After a complete code revision and a GUI version of GCLC for Linux made in 2015, now in 2020, it is another big step for GCLC: it goes open-source! Please find the links to the source code and to current versions of executables in the Downloads section. Predrag Janičić [home page] December 2020
What is GCLC?	Main Features of GCLC	Downloads (Free)
GCLC (from "Geometry Constructions -> LaTeX Converter") is a tool for visualizing geometry, and for producing mathematical illustrations. Its main purposes are: producing digital mathematical illustrations of high quality; use in teaching geometry; use in studying geometry with the help of automated theorem provers. The basic idea behind GCLC is that constructions are formal procedures, rather than drawings. Thus, in GCLC, producing mathematical illustrations is based on "describing figures" rather than on "drawing figures". Created figures, of course, can be displayed and can be exported to LaTeX and other formats. Although GCLC was initially built as a tool for producing LaTeX figures from descriptions of geometric constructions, now it is much more than that. It provides easy-to-use support for many isometric transformations, conics, parametric curves, dealing with expressions, flow control, automated theorem proving, etc. There versions for Windows and for Linux. There are command line versions and versions with graphical user interfaces (that provide a range of additional functionalities). The very first version of GCLC was written in Nov 1995. GCLC had its first public release in 1996, and several releases since then. It has thousands of users wordwide and it has been used for producing digital illustrations for a number of books, journal articles, theses, and in a number of high-school and university courses worldwide.	Freely available; Support for a range of elementary and compound constructions, and isometric transformations; Support for symbolic expressions, second order curves, parametric curves, flow control, user-defined functions, etc; User-friendly interface, interactive work, animations, tracing points, "watch window" ("geometry calculator"), and other tools; Support for drawing trees and graphs; Built-in automated theorem provers, capable of proving many complex theorems; Simple, easy to use, small in size; Export of high quality figures into LaTeX (simple LaTeX format, PSTricks format, TikZ format), EPS (Encapsualted PostScript), SVG (Scalable Vector Graphics), bitmap, PNG, JPG format; Command line and version with graphical user interface both for Windows and Linux; Import from JavaView JVX format.	Open source (git repository with source code and pre-built executables for Linux and Windows, available since Dec 5, 2020): github repo Current release (command line version (gclc), GUI version (gclc-gui), manual, sample files, etc. (current version June 20, 2022): Linux version Windows version GCLC Manual The original address of this page is: www.matf.bg.ac.rs/~janicic/gclc (mirrored versions are not always up-to-date) GCLC is available also from EMIS (The European Mathematical Information Service) servers: http://www.emis.de/misc/software/gclc/.
Author(s)	Feedback Welcome	Copyright Notice
GCLC is being developed by Predrag Janičić (Faculty of Mathematics, University of Belgrade) and, in some parts, by Predrag Janičić and his coauthors: Ivan Trajković (University of Belgrade, Serbia) - coauthor of the graphical user interface for the Windows version WinGCLC (2003); Pedro Quaresma (University of Coimbra, Portugal) - coauthor of the theorem prover based on the area method; Goran Predović (University of Belgrade, Serbia) - the main author of the theorem provers based on the Wu's methods and on the Groebner bases method; Luka Tomašević (University of Belgrade, Serbia) - the main author of the support for graph drawing; Konrad Polthier and Klaus Hildebrandt (Technical University, Berlin, Germany) - coauthors of the JavaView to GCLC converter). Pedro Quaresma (University of Coimbra, Portugal), Jelena Tomašević (University of Belgrade, Serbia), Milena Vujošević-Janičić (University of Belgrade, Serbia) - coauthors of the support for XML.	If you use GCLC package, please let me know by sending an e-mail to (Predrag Janicic); I will put you on the GCLC mailing list and inform you about new releases of GCLC. Please send me your comments and suggestions to . Your feedback would be very much appreciated and would help in improving the future releases of GCLC. If you used GCLC for producing figures for your book or a paper, I would be happy to hear about that. Please send me your GCLC gems and I will put them on this page.	This software is protected by the Creative Commons licence CC BY-ND: Attribution-NoDerivatives 4.0 International. This license allows for redistribution, commercial and non-commercial, as long as it is passed along unchanged and in whole, with credit to the author. You may install and run this untouched software without any restrictions. All output of this software is your property. You are free to use it in teaching, studying, research, and in producing digital illustrations. THIS SOFTWARE IS PROVIDED "AS IS" AND WITHOUT ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. (c) Predrag Janicic 1995-2022

Prof. Zoran Lucic (University of Belgrade, Serbia): Euclid's construction of dodecahedron (2005)	Prof. Zoran Lucic (University of Belgrade, Serbia): Archita's construction of cube doubling (2006)	Bojan Radusinovic (Serbia): Pythagora's theorem (2007)
Prof. Pierre Larochelle (USA): 3D circles (2008)	Prof. Pierre Larochelle (USA): Spherical quadrilateral (2008)	Robert Hartmann (Germany): Hyperboloid (2009)
Thomas Speziale (USA): Golden Spiral (2007)	Ania Piktas (Poland): The Koch curve (2007)
Milan Mitrović (Slovenia): four figures from his textbook on projective geometry (2007)	Vladimir Baltic (Serbia): several figures from his book textbook on discrete mathematical structures (2010)
Prof. Ebert Brea (Venezuela): Convolution between two functions (2023)	Prof. Ebert Brea (Venezuela): Karush–Kuhn–Tucker Conditions (2023)

More on the background of GCLC can be found in:

• Predrag Janicic and Ivan Trajkovic: WinGCLC --- a Workbench for Formally Describing Figures. In Proceedings of the 18th spring conference on Computer graphics (SCCG 2003), pages 251--256, Budmerice, Slovakia, April, 24-26 2003. ACM Press, New York, USA.
• Mirjana Djoric and Predrag Janicic. Constructions, instructions, interactions. Teaching Mathematics and its Applications, 23(2):69--88, 2004.
• Pedro Quaresma and Predrag Janicic. Framework for the Constructive Geometry. Technical Report TR2006/001, Center for Informatics and Systems of the University of Coimbra, 2006.
• Pedro Quaresma and Predrag Janicic. Integrating dynamic geometry software, deduction systems, and theorem repositories. In J. Borwein and W. Farmer, editors, Mathematical Knowledge Management (MKM-2006), volume 4108 of Lecture Notes in Arti cial Intelligence, pages 280-294. Springer-Verlag, 2006.
• Predrag Janicic and P. Quaresma. System description: GCLCprover + GeoThms. In U. Furbach and N. Shankar, editors, International Joint Conference on Automated Reasoning (IJCAR-2006), volume 4130 of Lecture Notes in Artificial Intelligence, pages 145-150. Springer-Verlag, 2006.
• Predrag Janicic. GCLC - A Tool for Constructive Euclidean Geometry and More than That. In N. Takayama, A. Iglesias, and J. Gutierrez, editors, Proceedings of International Congress of Mathematical Software (ICMS 2006), volume 4151 of Lecture Notes in Computer Science, pages 58-73. Springer-Verlag, 2006.
• Predrag Janicic. Geometry Constructions Language, Journal of Automated Reasoning, 44(1-2): 3-24 (2010).
• Predrag Janicic, Julien Narboux, Pedro Quaresma: The Area Method - A Recapitulation. Journal of Automated Reasoning 48(4): 489-532 (2012)

I am grateful to:

• Prof. Mirjana Đoric for the initial discussion which led to the first version of GCLC (1995);
• Prof. Neda Bokan and other members of the Group for geometry, education and visualization with applications (mostly based at the Faculty of Mathematics, University of Belgrade) for their invaluable support in developing the WinGCLC release (2003);
• EMIS (The European Mathematical Information Service) for mirroring this page at http://www.emis.de/misc/software/gclc/) and other EMIS locations;
• DAAD (Germany) for funding my visit to Konrad Polthier's group at Mathematical Institute of TU Berlin (2003), which I used for making a JavaView->GCLC converter. I also thank Konrad Polthier and Klaus Hildebrandt for their warm hospitality and their collaboration in developing this program;
• CIM/CISUC (University of Coimbra, Portugal) for funding my visit to the Department of Mathematics, University of Coimbra (2005), which I used for developing the geometry theorem prover built into GCLC. I also thank prof. Pedro Quaresma for his warm hospitality and his collaboration in developing this prover;
• Prof. Bruno Buchberger (RISC, University of Linz, Austria), for kindly inviting me to visit RISC and to present GCLC there (2006).
• Prof. Stefano Marchiafava (University "La Sapienza", Rome, Italy), for kindly inviting me to visit the University "La Sapienza" and to present GCLC there (2008).
• My colleagues who coauthored some parts of GCLC: Goran Predović, Ivan Trajković, Luka Tomašević, Pedro Quaresma, Jelena Tomašević, Milena Vujošević-Janičić.
• James Fry (New Albany, Indiana, USA) for careful revision of the GCLC/WinGCLC manual file and many useful insights and comments (2005);
• Colleagues who gave useful comments and certain contributions and influenced development of GCLC: Nenad Dedić, Milos Utvić, Nikola Begović, Ivan Elčić, Jelena Grmuša, Aleksandra Nenadić, Marijana Lukić, Goran Terzić, Milica Labus, Srđan Vukmirović, Aleksandar Gogić, Aleksandar Samardžić, Ivan Čukić, and Nikola Ubavić;
• Vladimir Baltić (University of Belgrade), Konrad Polthier (TU Berlin), Zach (Temple University, USA), Hristos Bitos (Greece), Aleksandar Gogić (DTA, Belgrade), Bob Schumacher (Cedarville University, Ohio, USA), Biljana Radovanović (University of Belgrade), Nedeljko Stefanović (University of Belgrade), Milan Mitrović (Slovenia), Thomas Speziale (USA), Ania Piktas (Poland), Bojan Radusinović (Serbia), Pierre Larochelle (Florida Institute of Technology, USA), Robert Hartmann (TU Clausthal, Clausthal-Zellerfeld, Germany), and Xavier Allamigeon for useful feedback and suggestions on different versions of GCLC.
• All GCLC/WinGCLC users for their support, feedback and suggestions.