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Definition
*The memory isn't partitioned before * Memory is a sequence of variable-sized blocks -external fragmentation occurs *adjacent holes (right, left, or both) must be coalased to prevent fragmentation from increasing |
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Term
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Definition
| Unused space within partitions |
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Term
| 50% Rule (measures memory utilization) |
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Definition
| #holes = probability of inexact match * #full blocks / 2 |
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Term
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Definition
*Allows programs larger than physical memory *programs loaded as needed according to calling structure |
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*divided into fixed sized pages *one area of 0..n-1 words *more than intended can be copied to a page file |
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Term
| Segmented Virtual Memory (multiple segment) |
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Definition
*Multiple areas of up to 0..n-1 words *each holds a logical segment (eg function, data struct) *fragmentation possible *each is contiguous or divided into pages |
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Term
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Definition
*Combines paging and segmentation *every segment is divided into fix-size pages (becomes the best of both worlds if the blocks are tiny) |
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