This is most probably a dump file created by either the EXP, or EXPDP utility. You can use IMP (if it was EXP) or IMPDP (if it was EXPDP) to extract DDL from these files.
I don't know how to distinguish the two formats, my advice would be to try to access the files using IMPDP first, and it that fails, using IMP. All of these utilities are described in the documentation. It seems that in case of IMPDP, you can use the SQLFILE parameter to dump the DDL of contained DB objects. The IMP has a similar SHOW parameter.
There are usually log files created during import/export, if you had the import log file, you'd see what was exported and when. Perhaps you could obtain the log from the same source you obtained the DMP from?
sorry for late reply. this is an old DB dmp file. i think i will not be able to recover data from it as i know neither the user/pass used when exporting nor the log files.
all what i know is most of its tables ddl, IMP utility was not the key for recovering content.
Oracle's DMP files are not password protected. At least since Oracle 9i. I don't have experience with prior versions, but I believe these should be fairly backwards compatible.
Did you try to view the contents of the file in a text/hex viewer? An old DMP file I've found on my drive contains the text EXPORT:V10.02.01 right at the beginning of the file (after about three unreadable characters that probably form some part of a header).
It is of course possible that it is not proper Oracle dump file after all. Especially if the IMP/IMPDP tools refused to process the file.