ECC stands for
"ERP Central Component"
and is the subcessor or SAP R/3
The sequence is:
SAP R/3 4.6C
SAP R/3 Enterprise 4.7
SAP ECC 5.0
SAP ECC 6.0
Attention, the licence are different.
Is SAP ERP Central Component (ECC) - the technical successor of SAP R/3 covered of the existing licence agreement for SAP R/3 customers?
"No, ECC that is part of mySAP ERP software shipment is available to all customers that have a mySAP ERP or mySAP Business Suite license contract. Customers with a SAP R/3 license contract have the opportunity to convert their existing R/3 licenses, including a discount, either to a mySAP ERP contract or mySAP Business Suite contract. A customer with a mySAP Business Suite contract (formerly called 'mySAP.com' contract) has no need for a conversion, since a mySAP ERP license included in the mySAP Business Suite contract."
try this link