Multiple rings of protection were among the most revolutionary concepts introduced by the Multics operating system, a highly secure predecessor of today's Unix family of operating systems. The GE 645 mainframe computer did have some hardware access control, but that was not sufficient to provide full support for rings in hardware, so Multics supported them by trapping ring transitions in software; its successor, the Honeywell 6180, implemented them in hardware, with support for eight rings. However, most general-purpose systems use only two rings, even if the hardware they run on provides more CPU modes than that. For example, Windows 7 and Windows Server 2008 (and their predecessors) use only two rings, with ring 0 corresponding to kernel mode and ring 3 to user mode, because earlier versions of Windows ran on processors that supported only two protection levels.
We choose the best for you, photos and description to them!
5800 Fulton Ave, Van Nuys, CA 91401, US