At the beginning of the INCA Consortium work in 1982, no specific general astrometric catalogue of double and multiple stars was available, and the construction of such a catalogue was therefore undertaken. This project is being carried out at the Observatoire Royal de Belgique (Dommanget 1983, 1989), under the name of the `Catalogue of Components of Double and Multiple Stars' (CCDM). The original basis of this catalogue is the Index Catalogue of Visual Double Stars (Jeffers et al. 1963) augmented by a number of measurements collected at the US Naval Observatory by C.E. Worley and transmitted to the Meudon (later to the Nice) and Royal Greenwich Observatories until 1976. For logistical reasons, the WDS (Washington Visual Double Star Catalog, Worley & Douglass 1984) was not used. The CCDM has been complemented during the years 1982-91 by more than 40000 accurate positions and proper motions for individual components, compiled at the Astronomisches Rechen-Institut at Heidelberg (CDA, Bastian & Lederle 1985) or observed within the framework of the INCA Consortium Working Group on Double Stars.
The CCDM includes about 63000 systems, and aims to provide (for each component) accurate positions (better than one arcsec), proper motions, and cross-identifications with the most important reference and fundamental catalogues.