The Client application can specify the user ID and password by setting eci_userid and eci_password or eci_userid2 and eci_password2 in the ECI parameter block.
Use eci_userid and eci_password if the user ID and password names are 8 characters or less in length, or eci_userid2 and eci_password2 if the names can be more than 8 characters in length.
You can set a default user ID and password for the connection. See Making ESI V1 calls from C and COBOL programs for more information.