OS and Memory Management Flashcards
What are the 3 types of memory management?
Paging
Segmentation
Virtual Memory
What are the scheduling algorithms?
Round Robin
First come first served
Multi-level feedback queues
Shortest job first
Shortest remaining time
What are the types of OS?
Distributed
Embedded
Multi-tasking
Multi-user
Real Time
Define the term OS.
The term ‘operating system’ refers to a collection of programs that work together to provide
an interface between the user and computer.
What is the purpose of using an OS?
Memory management
Interrupt Service Routines
Processor Scheduling
Backing store management
Management of all input and output
What are the features that an OS provides?
- Memory management (paging, segmentation, virtual memory)
- Resource management (scheduling)
- File management (moving, editing, deleting files and folders)
- Input/ Output management (device drivers)
- Interrupt management
- Utility software (disk defragmenter, backup, formatting etc.)
- Security (firewall)
- User interface
One of the roles of OS is
to determine and allocate the length of processor time each task receives through the use of paging, segmentation and virtual memory
What is paging?
Paging is when memory is split up into equal-sized sections known as pages, with programs being made
up of a certain number of equally-sized pages. These can then be swapped between main memory and the hard disk as needed.
What is segmentation?
Segmentation is the splitting up of memory into logical sized divisions, known as segments, which vary in size. These are representative of the structure and logical flow of the program, with segments being allocated to blocks of code such as conditional statements or loops.
What is Virtual memory ?
Virtual memory uses a section of the hard drive to act as RAM when the space in main memory is insufficient to store programs being used. Sections of programs that are not currently in use are temporarily moved into virtual memory through paging, freeing up memory for other programs in RAM.
What is the key issue with using paging, segmentation, and virtual memory?
The key issue with using these three techniques is disk thrashing.
What is disk trashing?
This is when the computer ‘freezes’ because of pages being swapped too frequently between the hard disk and main memory.
What are the results of when a computer is said to be disk thrashing?
More time is spent transferring pages between main memory and the hard disk than is spent actually running the program. This issue becomes progressively worse as virtual memory is filled up.
