COMPUTER SCIENCE 005 OVERVIEW (42517) Partition Selection Algorithms First fit: allocates to the first partition big enough to hold it. Best fit: allocates to the smallest needed to hold it. Worst fit: allocates to the biggest number that can hold it. Paged Memory Management Processes divided into fixedsized pages and stored in frames when loaded. Frame: fixedsize portion of main memory that holds a process page. Page: fixedsize portion of a process stored into a memory frame. *** Frame and page are the same size *** Offset: remainder of the address divided by the page size. New logical address is mapped to physical address with the help of the page map table (PMT). Demand paging: pages are brought into memory on demand. Page swap: Bringing a page from the secondary memory, which often causes another page to be written back into secondary memory. Virtual memory: no restrictions on the size of a program. An entire process doesnt have to be in memory at the same time.