How does one iterate through items and records in a specified block?

One can use NEXT_FIELD to iterate (loop) through items in a specific block and NEXT_RECORD to iterate through records in a block. Code example:

            OriPos := TO_NUMBER(:System.Trigger_Record);

            First_Record;

            LOOP

              --   do processing

              IF (:System.Last_Record = 'TRUE') THEN

                 Go_Record(OriPos);

                 EXIT;

              ELSE

                 Next_Record;

              END IF;

            END LOOP