sentences:  However, it introduced a new file system which was not compatible with the original AOS and AOS/VS file system and also contained new features like Access control list (ACL) groups.Since some customers did not want to upgrade to the new file system, or invest in new hardware, Data General agreed to continue bug-fix support of an “immortal” revision of AOS/VS, which became known colloquially as AOS/VS “Classic”, while new development would proceed as AOS/VS II, with revision numbers rolled back to 1.00.Both VS-Classic (rev 7.7x) and VS-II (rev.