The files are organised sequentially and compressed and, within the files, the entries are sorted by star number and source reference. Due to the small size of many files, there is no need for indexing or direct access.
The filenames reflect their content and are conserved throughout the data base. They are presented in Appendix D. The command names are usually identical to that of the data type they handle.
This file organisation offers several advantages: it allows the full use of UNIX file handling tools for searching and sorting and has enabled the straightforward implementation of graphics facilities. Compressing the files with the system function compress produces a reduction of disk storage by a factor of two. Many tasks can be performed without physically decompressing the files, by using the system function zcat to feed a pipe; it produces an output but leaves the files compressed. Finally, Unix editors are used to maintain the files, saving software development.