Call to C-Programms

is there anybody out there, who can give me hints how to call C-Programms from stored Procedures. I've written a RPC-call which is storing certain values in an ORACLE DB. This programm must be called under certain conditions, which can be evaluated with data from the Database but how can I call the C programm ???

Thanks for any help

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Peter Wuebbelt                        wbb_at_ifm.mh-hannover.de    
Medizinische Hochschule Hannover      Tel: (0511) 5324413    
Institut fuer Biometrie               Fax: (0511) 5324295 
30623 Hannover