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Questions and Answers
What is the purpose of transferring low priority processes to a reserved memory area in secondary storage?
What is the purpose of transferring low priority processes to a reserved memory area in secondary storage?
What is the primary function of the long-term scheduler?
What is the primary function of the long-term scheduler?
What occurs during context switching?
What occurs during context switching?
What is the purpose of virtual memory?
What is the purpose of virtual memory?
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Which type of scheduler is responsible for selecting the next process to run from the ready queue?
Which type of scheduler is responsible for selecting the next process to run from the ready queue?
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What is the result of swapping low priority processes to secondary storage?
What is the result of swapping low priority processes to secondary storage?
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What occurs when a higher priority process arrives in the queue?
What occurs when a higher priority process arrives in the queue?
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What is the relationship between virtual memory and main memory?
What is the relationship between virtual memory and main memory?
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What is the primary goal of memory management in operating systems?
What is the primary goal of memory management in operating systems?
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What is the term used to describe the process of transferring processes between main memory and secondary storage?
What is the term used to describe the process of transferring processes between main memory and secondary storage?
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Study Notes
Memory Allocation Techniques
- There are three main memory allocation techniques used by an Operating System (OS): Contiguous, Linked, and Indexed.
Contiguous Memory Allocation
- Allocates disk space for a file as a single, contiguous block of storage.
- All sectors or clusters required to store a file are located together in a sequential manner on the disk.
- Advantages include easy implementation in ROM (Read-Only Memory) type storage media.
- Disadvantages include limitations in dynamic file size changes and inefficient use of disk space.
Linked Memory Allocation
- Allocates disk space for files in a non-contiguous manner using a linked list data structure.
- Each block of disk space contains a link (pointer) to the next block in the sequence, forming a chain of blocks that make up the file.
- The directory entry contains the starting block's address.
- Easy to extend file size by updating the last block in the sequence.
Indexed Memory Allocation
- Allocates disk space for files in a non-contiguous manner using an index (allocation table or allocation map).
- Each file is assigned a unique index block, which contains a list of pointers to the blocks of disk space allocated to the file.
- The index block also contains metadata such as the file's size and attributes.
Fragmentation and Defragmentation
- Fragmentation occurs when files are stored in non-contiguous blocks (fragments) on a storage device.
- Fragmentation can occur naturally over time as files are created, modified, and deleted on the disk.
- Defragmentation is the process of reorganizing the fragments into contiguous blocks to improve disk performance and efficiency.
Process Management
- A program is a set of instructions that define a task.
- A process is an instance of a program in execution, including current activity, memory, and system resources.
Virtual Memory
- Virtual memory is a reserved memory area in secondary storage used to transfer low-priority processes from main memory.
- Transferring between virtual memory and main memory is known as swapping.
- Virtual memory allows for more efficient use of main memory.
Schedulers
- There are three types of schedulers: Long-term, Mid-term, and Short-term.
- Long-term schedulers decide which programs to load into memory.
- Mid-term schedulers decide which suspended processes to load back into memory.
- Short-term schedulers decide which process to execute next.
Context Switching
- Context switching involves deallocating the CPU from the currently running process and allocating it to another process.
- It involves switching the context (including the running state) of the CPU between processes.
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Description
This quiz covers the three main memory allocation techniques used by an Operating System, including contiguous, linked, and indexed memory allocation.
