There have been a LOT of previous forum postings on the use of DICTIONARY.TABLES or the "dictionary" information that is maintained by SAS. Another "view" of the dictionary files are the SASHELP.Vxxx files -- SASHELP.VCOLUMNS, SASHELP.VTABLES, etc.
There are also a lot of user group papers on these topics with very good examples about how to use the meta-information in these files to help you manage your libraries and write data-driven programs.
I recommend that you search the forum postings on the terms
dictionary.tables or sashelp tables