BDC

 Functional modules  in BDC
    BDC_OPEN_GROUP - Name of the client, sessions and user name given
    BDC_INSERT -Used to insert the data for one transaction into a session.  
    BDC_CLOSE_GROUP - Used to close the batch input session.

 Data input entered by user simulated in BDC by data packet.

 Data packet is an internal table has a structure of BDCDATA, it has fields:
            1. PROGRAM (program name)
            2. DYNPRO (screen number) 
            3. DYNBEGIN (New screen start) X=new screen
            4. FNAM (Field name)
            5. FVAL (Field value)