Memory Allocation
Main memory usually has two partitions −
- Low Memory − Operating system resides in this memory.
- High Memory − User processes are held in high memory.
Operating system uses the following memory allocation mechanism.
| S.N. | Memory Allocation & Description |
|---|---|
| 1 |
Single-partition allocation
In this type of allocation, relocation-register scheme is used to protect user processes from each other, and from changing operating-system code and data. Relocation register contains value of smallest physical address whereas limit register contains range of logical addresses. Each logical address must be less than the limit register.
|
| 2 |
Multiple-partition allocation
In this type of allocation, main memory is divided into a number of fixed-sized partitions where each partition should contain only one process. When a partition is free, a process is selected from the input queue and is loaded into the free partition. When the process terminates, the partition becomes available for another process.
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