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Questions and Answers
What type of fragmentation is caused by allocating fixed-size memory blocks and leaving unused space within a block?
What type of fragmentation is caused by allocating fixed-size memory blocks and leaving unused space within a block?
Which memory management technique is used to minimize external fragmentation by dividing a process into equally sized pages?
Which memory management technique is used to minimize external fragmentation by dividing a process into equally sized pages?
Which of the following best describes virtual memory?
Which of the following best describes virtual memory?
In the context of memory, which of the following best differentiates main memory from secondary memory?
In the context of memory, which of the following best differentiates main memory from secondary memory?
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What is a potential disadvantage of segmentation in memory management?
What is a potential disadvantage of segmentation in memory management?
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What is a characteristic of main memory?
What is a characteristic of main memory?
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What is the main drawback of external fragmentation in memory management?
What is the main drawback of external fragmentation in memory management?
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What type of fragmentation is addressed by dynamic partitioning techniques?
What type of fragmentation is addressed by dynamic partitioning techniques?
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Which memory partitioning technique results in no internal fragmentation?
Which memory partitioning technique results in no internal fragmentation?
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Which placement algorithm chooses the block closest to the requested size?
Which placement algorithm chooses the block closest to the requested size?
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What does virtual memory provide for processes?
What does virtual memory provide for processes?
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What is a primary advantage of virtual memory paging?
What is a primary advantage of virtual memory paging?
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Why is fixed partitioning not commonly used in the industry today?
Why is fixed partitioning not commonly used in the industry today?
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How does dynamic partitioning differ from simple paging?
How does dynamic partitioning differ from simple paging?
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What differentiates secondary memory from main memory?
What differentiates secondary memory from main memory?
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What is the main purpose of virtual memory segmentation?
What is the main purpose of virtual memory segmentation?
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What is a key disadvantage of dynamic partitioning techniques?
What is a key disadvantage of dynamic partitioning techniques?
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What does the term 'overhead' refer to in memory management?
What does the term 'overhead' refer to in memory management?
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What limitation is present in dynamic partitioning regarding active processes?
What limitation is present in dynamic partitioning regarding active processes?
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Which concept refers to the operating system's ability to map virtual memory to real memory?
Which concept refers to the operating system's ability to map virtual memory to real memory?
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What challenge can arise from using compression techniques in memory management?
What challenge can arise from using compression techniques in memory management?
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Study Notes
Memory Management
- Memory management is a function of the operating system (OS)
- Manages the movement of processes between main and secondary memory
- Tracks memory allocation (allocated or free) for each process
- Facilitates process allocation and updates memory statuses
Types of Addresses
- Symbolic addresses: Used in source code (variable names, constants, instruction labels)
- Relative addresses: Addresses at compilation time; compiler converts symbolic addresses
- Physical addresses: Addresses generated by the loader when a program is loaded into memory
Memory Management Terms
- Frame: Fixed-length block of main memory
- Page: Fixed-length block of data in secondary memory (can be copied to a frame)
- Segment: Variable-length block of data in secondary memory (can be copied, or divided into pages)
- Swapping: Mechanism to move processes temporarily between main and secondary memory for more space
- Fragmentation: Memory spaces become smaller fragments due to continuous loading/removal of processes.
Memory Management Requirements
- Relocation: Programs can be moved in memory during execution (for swapping), avoiding programmer knowledge of exact locations
- Protection: Each process's memory is protected from interference by other processes, preventing unauthorized access
- Sharing: Multiple processes can access the same memory area (for cooperation or shared data)
- Logical organization: Programs organized into modules (some are fixed and some are modifiable), offering an advantage to the OS and hardware
- Physical organization: System responsibility to move and organize information between main and secondary memory.
Memory Types
- Main memory: Volatile memory, fast access, relatively high cost, holds currently used programs and data
- Secondary memory: Non-volatile memory, cheaper than main memory, slower access, stores programs and data for long-term storage
Memory Partitioning Techniques
- Fixed Partitioning: Pre-defined partitions of a fixed size for loading (less efficient use of memory - common internal fragmentation)
- Dynamic Partitioning: Dynamically created partitions to fit process size; more efficient but prone to external fragmentation
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Placement Algorithms (Dynamic Partitioning):
- Best-fit: Choose the partition closest in size to that required.
- First-fit: Scan the memory from beginning and select the first available partition.
- Next-fit: Scan memory starting from last placement for next available partition.
Simple Paging
- Divides memory into equally sized frames
- Processes divided into equally sized pages
- Pages loaded to available frames
Simple Segmentation
- Processes divided into segments
- Segments loaded to dynamic partitions
- No internal fragmentation (better memory utilization)
Virtual Memory (abstraction of main memory)
- Provides private address space for processes and kernel
- Allows multitasking
- Supports oversubscription and mapping between main and secondary memory (on demand)
- Virtual Memory Paging (similar to simple paging), but loads only necessary pages to reduce memory use.
- Virtual Memory Segmentation is similar, loading only required segments.
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Description
This quiz covers the essential concepts of memory management within operating systems. It explores types of addresses, management terms, and the processes involved in tracking memory allocation. Test your understanding of memory frames, pages, segments, and related terminologies.
