A VIDF may or may not contain a version information line. Those that do not have an implicit version of V2.1. This is placed into the file when it is converted into binary format. Those VIDF files which do have an explicit version number are given the version number listed in the VIDF version field.
If the VIDF has a version number associated with it then that field has the format:
Sample VIDF VERSION field:V VN.M /* Version Num */
The leading V in the version number is required. The following N and M are the major and minor version numbers respectively. These numbers indicate under which format definition the UDF was created and are used in the UDF kernel software when reading and parsing the UDF data.
NOTE: The version number is not a number used to indicate the version of the VIDF contents. The value should never be changed from what it is set unless the format of the UDF itself has been reworked and upgraded to a later format definition. To register changes in the values within a VIDF you should set up a CHANGE LOG in the comments field and use that.