Acknowledgements.

I am grateful to Th. M. Liebling who provided me with an ideal opportunity to visit EPFL for the academic year 1993-1994. Without his support, the present form of this program would not have existed. Later, H.-J. Lüthi (ETHZ) joined to support the the development of cdd codes (cdd, cdd+, cddlib). There are many people who helped me to improve cdd, in particular, I am indebted to David Avis, Alexander Bockmayr, David Bremner, Henry Crapo, Istvan Csabai, Francois Margot, Marc Pfetsch, Alain Prodon, Jörg Rambau, Shawn Rusaw, Matthew Saltzman, Masanori Sato and those listed in the HISTORY file.