Contiguous Memory Allocation and Fragmentation
Main memory must hold the kernel and several user processes at once. The simplest scheme gives each process one contiguous block of physical memory.
Operating Systems · topic
Memory management and paging
Contiguous allocation with relocation and limit registers, first, best, next and worst fit, internal and external fragmentation, segmentation tables, paging address splits, page-table sizes, multilevel, inverted and hashed page tables.
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Paging, Page Tables and TLB
Paging removes external fragmentation by giving up contiguity. The logical address space of a process is cut into fixed-size pages, physical memory into frames of the same size, and any page can sit in any free frame.
Segmentation
A programmer does not think of a program as one linear array of bytes. It is a collection of logical units: the main code, a few library modules, global data, a heap and a stack, each of a different size and each able to grow on its own.
Memory management and paging cheat sheets
One-page visual sheets for this topic, in the sheet library on the store. Previews are free; the full sheets come with the subject pack.