Writing an Add/Change/Delete/Inquiry maintenance program

This is the DDS for the Physical File named CUST.

     A          R CUSTR                     TEXT('CUSTOMER')      
     A            CUS#           6S 0       TEXT('CUST #')        
     A            CUSNAM        30A         TEXT('NAME')          
     A            CUSAD1        30A         TEXT('ADDRESS 1')     
     A            CUSAD2        30A         TEXT('ADDRESS 2')     
     A            CUSCTY        20A         TEXT('CITY')          
     A            CUSSTA         2A         TEXT('STATE')         
     A            CUSZIP         5S 0       TEXT('ZIP')           
     A          K CUS#