Fmt Definitions are kept in special Dictionaries named "${DDSROOT}/src/lib/dds3/format.fmt.dds". They include the fmt conversion Definitions also which normally do not appear in the data Dictionary. Only the derived fmt Definitions are placed there.

Dictionary      Format
--------------  ------
usp.fmt.dds     usp
segy.fmt.dds    segy, su
segy1.fmt.dds   segy Rev. 1
asp.fmt.dds     Generic DDS (asp, sep, cube, ...)
    

The use can modify these fmt Definitions by either overriding any of them on the command line; or by modifying one of these fmt Dictionaries and point DDS to it by specifying "DDS_PATH" to have the pathname to the modified fmt Dictionary. A user may provide a fmt Dictionary for custom formats. The first Dictionary in "DDS_PATH" that matches the new format name is used to define the binary format, otherwise internal default fmt specifications are used.