Non Contiguous Memory Allocation Quiz

Memory Allocation

• Non-contiguous memory allocation refers to a technique where a program's memory is divided into multiple segments, each of which can be allocated separately, allowing for more efficient use of memory.

Segmented Memory Allocation

• Segmented memory allocation divides a program's memory into multiple segments, including:
  • Code segment
  • Data segment
  • Stack segment
  • Heap segment
• Each segment has a base address and a limit, which define the range of addresses that can be used within that segment.

Addressing Scheme for Segmented Memory Allocation

• The addressing scheme for segmented memory allocation requires a two-dimensional logical address, consisting of:
  • Segment number (s)
  • Offset (d)
• This allows the system to calculate the physical address using the segment table.

Advantages of Segmented Memory Allocation

• One advantage of segmented memory allocation is that it allows multiple programs to share the same code segment, reducing memory usage.

Segment Table

• The segment table is a data structure that stores the base address and limit of each segment, allowing the system to map logical addresses to physical addresses.

Mapping Logical to Physical Address

• In the segmentation process, a two-dimensional logical address (s, d) is mapped to a one-dimensional physical address using the segment table, which provides the base address of the segment, and the offset, which is added to the base address to calculate the physical address.

Disadvantages of Dynamic Memory Allocation

• The main disadvantage of dynamically allocated memory in the context of variable-length segments is that it can lead to fragmentation, where free memory is broken into small, non-contiguous blocks, making it difficult to allocate large blocks of memory.

Paging

• Internal fragmentation in the context of paging refers to the wasted space within a page, resulting from the fact that the page size is fixed, but the amount of data to be stored may not exactly fill the page.

Page Table

• The page table is a data structure that stores the mapping of logical page numbers to physical page numbers, allowing the system to translate logical addresses to physical addresses.

Paging Hardware

• In the paging hardware, the page number (p) refers to the logical page number, which is used to index the page table to retrieve the corresponding physical page number.