Operating System Memory Management

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Questions and Answers

What is the main purpose of relocation in memory management?

To maximize processor utilization by swapping processes (correct)

To allow multiple processes to share memory

To protect processes from unauthorized access

To manage logical organization of program modules

Which requirement of memory management ensures that processes cannot interfere with each other's memory?

Logical organization

Protection (correct)

Physical organization

Relocation

What advantage does sharing provide in memory management?

It simplifies the task of moving data to secondary memory

It categorizes processes into fixed partitions

It enables multiple processes to access the same program copy (correct)

It allows processes to modify their own memory modules

What type of memory is considered volatile and provides fast access?

Main memory Signup and view all the answers

Which statement best describes fixed partitioning in memory management?

It divides main memory into static partitions at system generation time Signup and view all the answers

What is a significant drawback of fixed partitioning?

It often results in internal fragmentation Signup and view all the answers

Which requirement relates to the effective management of user programs and data into modules?

Logical organization Signup and view all the answers

What primary characteristic distinguishes secondary memory from main memory?

Secondary memory typically has larger capacity and is non-volatile Signup and view all the answers

What aspect of memory management does dynamic partitioning specifically eliminate?

Internal fragmentation Signup and view all the answers

Which placement algorithm scans memory from the beginning and selects the first adequate block?

First-fit Signup and view all the answers

What is a drawback of simple segmentation?

External fragmentation Signup and view all the answers

How does virtual memory impact multitasking in operating systems?

It provides private address space for processes. Signup and view all the answers

What is the primary role of simple paging in memory management?

Implement virtual memory using fixed-size frames. Signup and view all the answers

Which type of fragmentation is specifically reduced by simple paging?

External fragmentation Signup and view all the answers

What is a feature of dynamic partitioning concerning memory use?

It results in inefficient processor use. Signup and view all the answers

Which statement best describes virtual memory?

It enables programs to exceed the physical memory limits. Signup and view all the answers

What is the primary role of an operating system in memory management?

It manages the movement of processes between main and secondary memory. Signup and view all the answers

Which of the following types of addresses is generated when a program is loaded into the main memory?

Physical addresses Signup and view all the answers

What occurs when external fragmentation develops?

Small free memory spaces arise from varying block sizes. Signup and view all the answers

What process is described as swapping a process temporarily out of the main memory?

Swapping Signup and view all the answers

In the context of memory management, what is a frame?

A fixed-length block of main memory. Signup and view all the answers

Which term describes the condition when allocated memory blocks are of fixed size leading to unused space?

Internal fragmentation Signup and view all the answers

What is the primary purpose of a page in memory management?

To act as a fixed-length block of data in secondary memory. Signup and view all the answers

What is indicated by the term 'fragmentation' in memory management?

The occurrence of small unused memory spaces due to process loading and removal. Signup and view all the answers

What type of applications are classified as CPU-bound?

Applications performing heavy compute operations Signup and view all the answers

Which scheduling algorithm selects processes based on the shortest expected processing time?

Shortest Job First (SJF) Signup and view all the answers

What characteristic defines a non-preemptive scheduling algorithm?

Execution continues until the process terminates or blocks Signup and view all the answers

In which situation would the preemptive scheduling algorithm be used?

When a new process arrives Signup and view all the answers

What is a primary drawback of the First-Come First-Serve (FCFS) scheduling algorithm?

It has a high average waiting time for processes. Signup and view all the answers

Which of the following defines Shortest Remaining Time First (SRTF) scheduling?

It is a preemptive version of Shortest Job First (SJF). Signup and view all the answers

What is a common issue associated with the Shortest Remaining Time First (SRTF) scheduling algorithm?

Starvation of long processes Signup and view all the answers

Which application type typically benefits most from I/O-bound processing?

Web servers and file servers Signup and view all the answers

What is a key feature of virtual memory paging?

Can lead to a higher degree of multiprogramming Signup and view all the answers

What role does the long-term scheduler play in process scheduling?

Determines which programs are admitted to the system Signup and view all the answers

Which of the following describes a ready queue?

Holds processes that are ready to execute in main memory Signup and view all the answers

What is the primary objective of short-term scheduling?

To increase the system performance through immediate scheduling Signup and view all the answers

What is a unique characteristic of virtual memory segmentation?

It has no external fragmentation Signup and view all the answers

Which process scheduling does not focus on immediate CPU allocation?

Job scheduling Signup and view all the answers

What does the device queue contain?

Processes waiting for device availability Signup and view all the answers

What differentiates medium-term scheduling from other forms of scheduling?

It addresses the swapping function in OS management Signup and view all the answers

What does the scheduler do in a Shortest Job First (SJF) algorithm?

Chooses the process with the shortest expected remaining processing time Signup and view all the answers

Which characteristic best describes the Round Robin (RR) scheduling algorithm?

It uses a clock interrupt for preemption of processes. Signup and view all the answers

What risk is associated with Non-Preemptive Priority (NPP) Scheduling?

Lower-priority processes may suffer from starvation Signup and view all the answers

What happens to a process in Round Robin scheduling once it consumes its quantum?

It is automatically preempted and placed back in the queue. Signup and view all the answers

In NPP Scheduling, what determines the execution order of processes with the same priority?

The order of arrival in the ready queue Signup and view all the answers

What is the primary focus of the Shortest Job First scheduling method?

Selecting the process with the shortest expected processing time Signup and view all the answers

Which of the following is a key feature of the Round Robin scheduling technique?

Each process is given a fixed time quantum. Signup and view all the answers

Which factor does NOT typically influence the priority of a process in Non-Preemptive Priority Scheduling?

The marketing strategy of the developing company Signup and view all the answers

Study Notes

Memory Management

Memory requirements management is a function of an operating system (OS) that controls primary memory and moves processes between main and secondary memory.
This function tracks memory locations (allocated or free) and allocates memory for processes.
Addresses in programs can be symbolic (source code), relative (compilation), or physical (loader generated).
Memory management uses terms like:
- Frame: Fixed-length block of main memory
- Page: Fixed-length block of data in secondary memory (copied to frame)
- Segment: Variable-length block of data in secondary memory (can be divided into pages)
- Swapping: Temporarily moving a process from main to secondary memory to free space. Also known as memory compaction.
- Fragmentation: Memory space is broken down into small fragments due to continuous loading and unloading of processes, making allocation challenging.
  - External fragmentation: Allocated memory blocks have variable sizes.
  - Internal fragmentation: Allocated memory blocks are fixed size, which may be wasteful if the process needs different space.
Memory management requirements:
- Relocation: Ability to move a program in main memory during swapping.
- Protection: Preventing processes from interfering with each other (accidental or purposeful).
- Sharing: Allowing multiple processes to access the same memory areas when appropriate.

Memory Organization

Programs have logical organization, often as modules (some read-only, etc.)
Physical organization divides memory into at least two levels:
- Main memory (volatile, fast, expensive). Holds currently used programs and data
- Secondary memory (non-volatile, slower, cheaper). Long-term storage of programs and data.

Memory Partitioning

Fixed partitioning: Divides memory into static partitions at system generation time, each with equal size.
Dynamic partitioning: Allocates partitions dynamically, where each partition matches the process requirements.. Algorithms include Best-Fit, First-Fit, and Next-Fit methods to find suitable memory locations.

Virtual Memory

An abstraction of main memory, giving processes and the kernel a large, almost unlimited address space.
Allows multitasking and manages processes and kernel resources even when memory is limited.
Uses abstraction (doesn't need to all be in real memory directly).
- Virtual memory paging and segmentation: Simpler versions of paging/segmentation that divide memory into segments or pages that may not all be loaded at once.

Process Scheduling

Process scheduling is managing which jobs or tasks are executed (and in what order).
This includes removing processes from the CPU and selecting the next process for the processor (usually).
Queues involved are:
- Job queue: List of all processes in a system
- Ready queue: Processes ready in main memory to execute
- Device queue: Processes waiting for an I/O device

Scheduling Criteria

Turnaround time (Tr): Time from submission until completion.
Response time: Time from request until response begins.
Burst time (Ts): Execution time of a process.
Waiting time: Time spent waiting in ready queue.
Throughput: Number of processes completed per unit of time.
Processor utilization (CPU utilization): Percentage of time the processor is busy.

Process Scheduling Algorithms

Several algorithms exist for scheduling processes, each with pros and cons in different scenarios:

First come first served (FCFS).
Shortest job first (SJF).
Shortest remaining time first (SRTF).
Round robin (RR): Time-sliced allocation.
Non-preemptive priority.

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Description

Test your knowledge on memory management within operating systems. This quiz covers essential concepts such as paging, segmentation, fragmentation, and address types. Understand how operating systems track and allocate memory for processes.