Memory Management part II

Dynamic linking requires operating system support. If the processes in memory protected each other, only the operating system that can check whether the required routine in memory. The operating system can also allow many processes access the same address memroy.

Overlays

Overlay is to divide the program into parts and then store instructions and data required in the main memory. Overlay does not require support from the operating system.

Logical and Physical Address Space

Logical address is the memory address derived by the CPU. Physical address is the actual memory addresses used by the memory unit. At compile time and load time, logical and physical address pointing the same address, but at a different execution time. At the logical address is called a virtual address. A logical collection of addresses that is derived by a program called a logical address space and the collection of physical addresses associated with the logical address space is called physicall address. Run-time occurs from the virtual address mapping to a physical address by the MMU (Memory Management Unit).

Swapping

Swapping is the process of moving a program in memory to a disk and then called back into memory to continue execution.




Contigous Allocation

The main memory is usually divided into 2 parts, the part for containing the operating system (always in memory) with an interrupt vector and the rest to the user process.
Single-Partition Allocation

It takes a protection against the code and data operating system to a change that occurs by the process of user memory and also protection of the processes of the user. Was used for relocation scheme limit-register and register. Relocation register contains value of smallest physical address and limit registers contain values of logical address ranges. Each logical address value must be less than the limit register. Relocation register provides a way to measure the code from the operating system can dynamically change the memory.