11.Hardware Protection

>when executing in monitor mode,the operating system has unrestricted access to both monitor and user's memory.

>the load instructions for the base and limit registers are privileged instructions.

>I/O Protection- must ensure that a user program could never gain control of the compute in monitor mode.

>Memory Protection- must provide memory protection at least for the interrupt vector and the interrupt service routines.

-in order to have memory protection, add two registers that determine the range of legal addresses a program may access;

-base register-holds the smallest legal physical memory address.

-limit register-contains the size of a range.

>CPU Protection-to prevent a user programs gets stuck in infinite loop and never returning back to the os