Operations Systems C3 Flashcards
What are the areas of improvement addressed by virtual memory systems?
continuous program storage
placement of the entire program in memory during execution
enhance Memory Manager performance
( particularly with cache memory)
How is an incoming job handled in paged memory allocation?
The incoming job is divided into pages of equal size, and memory manager tasks prior to program execution include determining the number of pages, locating empty page frames in main memory, and loading all program pages into these frames.
the mem managers task is to determine the no pages thats available and locate them to the empty page frames in the main memory
How does demand paging differ from paged memory allocation?
Demand paging loads only a part of the program into memory, removing the restriction of having the entire program in memory. It requires high-speed page access and exploits programming techniques for modules that are not needed simultaneously
very similar to page mem allocation - however pages are ONLY loaded when acutally needed,It removes the restriction of having the entire program in memory
What are two well-known page replacement algorithms?
Two well-known page replacement algorithms are First-in First-out (FIFO) and Least Recently Used (LRU).
What do the status, referenced, and modified bits in the Page Map Table represent?
The status bit indicates whether the page is currently in memory. The referenced bit shows if the page has been recently referenced, and the modified bit signifies whether the page contents have been altered.
How is memory allocated in segmented memory allocation?
Each job is divided into several segments, with one segment for each module. Memory is allocated dynamically based on the program’s structural modules.
What does segmented/demand paged memory allocation combine from segmentation and paging?
Segmented/demand paged memory allocation combines the logical benefits of segmentation with the physical benefits of paging.
Advantages of virtual memory include unrestricted job size,
efficient memory use
support for unlimited multiprogrammig.
Disadvantages include
higher processor hardware costs
increased overhead handling paging interrupts
heightened software complexity
BIG / Bigger jobs / improved memory use / great multitasking
Vs
CHI / Costly hardware / Handling delays / inc complexity
How does cache memory improve computer system performance?
Cache memory, being a small and high-speed intermediate memory unit, increases processor access speed compared to main memory. It stores frequently used data and instructions.
What are the main responsibilities of the Memory Manager in an operating system?
The Memory Manager is responsible for allocating memory storage in main memory, cache memory, and registers during program execution, and deallocating memory when the execution is completed.
What table is associated with page memory allocation
Page map table PMT
-Page No
Page Frame no
What are the 3 tables
Job Table JT
-job size
- page map table location
…………………………………………………
Page map Table PMT
-Page no
-Page Frame no
………………………………………………….
Memory map table MMT
-Page frame
-State
