Dictionaries contain a chronological sequence of definitions. DDS will normally scanf for definitions from the bottom up looking for the latest definition when there are multiple occurances for the same definition name. Each Dictionary is identified by its filename or a special mnemonic for internal dictionaries. Because anything written to a Dictionary will become a part of a Definition. Therefore, if you want to add a comment to a Dictionary, DO NOT simply do something like adding a "#" at the begining of a line. Instead simply create a new Definition with a name that is not normally used for anything such as "comment=...". All Definitions can expand across multipl lines until the next Definition is encountered.

Dictionary filenames have a few constraints:

• They should not terminate with ":" (colon). These names are reserved for mnemonic dictionaries.
  
  
• Filenames must not contain "=", white space, or control characters, as this would conflict with the basic definition structure.
  
  
• It is reccommended that other special characters and "white space" not be used in filename. Although this is possible, it can create confusion and difficulty dealing with these unusual types of filenames.
  
  
• Users may follow additional conventions. For example, dictionaries that describe binary data may be prefixed by "H" (History).

By default, disk files are created in the current working directory. The use of DATA_PATH (see Runtime Control) can be used to create Binary files in other directories.