<aside> 💬 Limited Direct Execution, LDE

for the most part, let the program run directly on the hardware; however, at certain key points in time, arrange so that the OS gets involved and makes sure the “right” thing happens.

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Dynamic Relocation

Using base and bounds

physical address = virtual address + base

Because this relocation of the address happens at runtime, and because we can move address spaces even after the process has started running, the technique is often referred to as dynamic relocation.

The base and bounds registers are hardware structures kept on the chip.

<aside> 💬 Memory Management Unit, MMU - The part of the processor that helps with address translation

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<aside> 💬 Two ways of the bound register:

1. Holds the size of the AS
2. Holds the PA of the end of the AS </aside>

Operating System Issues

1. The OS must take action when a process is created, finding space for its address space in memory.
2. The OS must do some work when a process is terminated
3. The OS must also perform a few additional steps when a context switch occurs.
   1. using per-process structures like process structure and process control block(PCB)
4. The OS must provide exception handlers, or functions to be called, as discussed above; the OS installs these handlers at boot time