Os Ch3 Flashcards
(22 cards)
What are the two parts of main memory in a uniprogramming system?
One part for the operating system and one part for the program currently being executed.
In a multiprogramming system, what must the user part of memory be subdivided for?
To accommodate multiple processes.
What is the task of the operating system regarding memory in a multiprogramming system?
Memory management.
Define ‘Frame’ in the context of memory management.
A fixed-length block of main memory.
What is a ‘Page’?
A fixed-length block of data that resides in secondary memory.
What does ‘Segmentation’ refer to?
A variable-length block of data that resides in secondary memory.
What are the memory management requirements?
Relocation, Protection, Sharing, Logical Organization, Physical Organization.
What does ‘Relocation’ mean in memory management?
The ability to share available main memory among multiple processes.
True or False: Each process should be protected against interference by other processes.
True.
What is the purpose of sharing in memory management?
To allow several processes to access the same portion of main memory.
How is main memory organized?
As a linear or one-dimensional address space.
What is the difference between main memory and secondary memory?
Main memory provides fast access and is volatile, while secondary memory is slower, cheaper, and usually not volatile.
What is overlaying in memory management?
Organizing program and data so that various modules can use the same region of memory.
Describe ‘Fixed Partitioning’.
Main memory is divided into static partitions at system generation time.
What is a disadvantage of Fixed Partitioning?
Main memory utilization is inefficient due to internal fragmentation.
What is ‘Dynamic Partitioning’?
Partitions created dynamically, allocating memory exactly as required.
What problem arises from Dynamic Partitioning over time?
External fragmentation.
What technique can be used to overcome external fragmentation?
Compaction.
What is the ‘First-fit’ algorithm?
Scans memory from the beginning to find the first available block that is large enough.
Describe the ‘Next-fit’ algorithm.
Scans memory from the location of the last placement to find the next available block that is large enough.
What is a disadvantage of the ‘Best-fit’ algorithm?
It can lead to more frequent need for memory compaction due to small fragments left behind.
What is the purpose of a replacement algorithm in a multiprogramming system?
To choose which process to swap out of main memory when there is insufficient memory.
