The PDB (Protein Data Bank) format is used to store coordinate or velocity data being input or output from NAMD. This is the standard format for coordinate data for most other molecular dynamics programs as well, including X-PLOR and CHARMm. A full description of this file format can be obtained via anonymous FTP from ftp.pdb.bnl.gov in /pub/format.desc.ps.Z or /pub/format.desc.txt.