A NAMD configuration file contains a set of options and values. The options and values specified determine the exact behavior of NAMD, what features are active or inactive, how long the simulation should continue, etc. Section 4.1 describes how options are specified within a NAMD configuration file. Section 4.2 describes the various parameters that are available and how to use them. Section 4.3 describes the relation between specific NAMD and X-PLOR dynamics options. Several sample NAMD configuration files are shown in section 4.4