Input (grade 13): System R also derived from Codd's theories, and Ellison wanted to make Oracle's product compatible with System R, but IBM stopped this by keeping the error codes for their DBMS secret.
Output (grade 10): System R was also based on Codd's theories. Ellison wanted to make Oracle's product compatible with System R, but IBM stopped this by keeping the error codes for their DBMS (DataBase Management System) secret.