Omron CJ - REFERENCE MANUAL 07-2009 Reference Manual page 191

Designating Command Parameters
Section 5-2
missible to specify 7E hex (–) at the first and second characters (consecutive)
of a file name.
If a file name has no extension, fill both the period (2E hex) and the extension
with 20 hex.
If the file name in response data has no extension, both the period (2E hex)
and the extension will be filled with 20 hex.
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