The Hipparcos and Tycho Catalogues This is one of the six CD-ROM sets containing the Hipparcos and Tycho Catalogues: astrometric and photometric star catalogues derived from the ESA Hipparcos Space astrometry mission. Contents of the Catalogues: Each of the catalogues includes a large quantity of very high quality astrometric and photometric data, as well as annexes featuring variability and double/multiple star data. In the case of the Hipparcos Catalogue, the principal parts are provided in both printed and machine-readable form. In the case of the Tycho Catalogue, results are provided in machine-readable form only. Although in general only the final reduced and calibrated astrometric and photometric data are provided, some auxiliary files containing results from intermediate stages of the data processing, of relevance for the more-specialised user, have also been retained for publication. The contents of the Hipparcos and Tycho Catalogues, and their associated annexes, have been distributed across the CD-ROM set. Each CD-ROM contains a complete catalogue or annex along with associated index files. Disc 1 also contains figures (lightcurves), tables, notes and references which are related primarily to the catalogues contained on that disc. Identification charts are found on disc 2, in addition to data files. The directory structure and contents, and data formats, are described in the printed documentation (Section 2.11 of Volume 1 "Introduction and Guide to the Data"), and in the corresponding files of that documentation in the directory `docs' (on disk 1). Data Format: The data in each catalogue file is stored in ASCII. The conventions adopted for writing these ASCII files are described in Section 2.11 of Volume 1. The Fortran format for each machine-readable catalogue or annex is given in the appropriate section of Volume 1. Users should note that the main data and index files are written with PC end-of-line characters (`carriage return' plus `line feed').
CD-ROM Format: This CD-ROM set is formatted for the ISO 9660 Standard, Data Interchange Level 1. File names at this interchange level are restricted to at most 8 characters, followed by a full-stop, ".", followed by at most a three-character extension, followed by a version number suffix, which is ";1" in every case. The appearance of the file names (uppercase or lowercase, with or without version numbers) depends on the computing platform, operating system, and device-driver software used to access the CD-ROM. Data Volume 6GB.