Operating Systems

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Questions and Answers

What does the Memory Management Unit (MMU) do?

Maps I/O device addresses to RAM.

Maps virtual addresses to physical addresses. (correct)

Maps physical addresses to logical addresses.

Maps logical addresses to disk space.

Which of the following statements about paging is true?

Physical memory must be divided into variable-sized blocks.

Paging requires additional memory for the page table. (correct)

Pages and frames can have different sizes.

Paging eliminates all forms of fragmentation.

What is the effect of preemptive scheduling on CPU processes?

Processes can be interrupted and placed back in the ready state. (correct)

Only high-priority processes can run without interruption.

All processes are treated equally without any preemption.

Processes run to completion without interruption.

How is the completion time of a process calculated?

Completion Time = Turnaround Time - Arrival Time Signup and view all the answers

What is meant by the term 'throughput' in the context of scheduling policies?

The number of processes completed per unit time. Signup and view all the answers

In paging, if the logical address space size is equal to the physical address space size, how will the number of pages compare to the number of frames?

They will always be equal. Signup and view all the answers

What does virtual memory allow applications to do?

Use more physical memory than is installed in the system. Signup and view all the answers

Which of the following is NOT a component of measuring CPU performance?

Memory Access Speed Signup and view all the answers

What type of operating system is designed to handle multiple programs running simultaneously and allows for user interaction with all of them?

Time sharing system Signup and view all the answers

Which file system feature is associated with NTFS but not FAT?

Provides encryption Signup and view all the answers

During memory management, which type of fragmentation occurs when allocated disk space is larger than the requested size?

Internal fragmentation Signup and view all the answers

What is a key advantage of linked allocation in file management?

No external fragmentation Signup and view all the answers

Which storage allocation method involves creating a table of pointers at the time of file creation?

Indexed allocation Signup and view all the answers

In disk formatting, what is the purpose of low-level formatting?

Marks cylinders and tracks on the disk Signup and view all the answers

Which of the following statement is true regarding external fragmentation?

It affects free block availability. Signup and view all the answers

Which feature of a real-time operating system is essential for applications that require high reliability?

Quick and predictable response times Signup and view all the answers

What does a Process Control Block (PCB) NOT contain?

User permissions Signup and view all the answers

Which of the following best describes an I/O bound process?

Process that spends more time waiting for I/O operations to complete. Signup and view all the answers

In which state is a process when it is waiting for I/O completion?

Wait/Blocked Signup and view all the answers

Which scheduling type primarily controls the degree of multiprogramming?

Long-term scheduling Signup and view all the answers

What triggers a context switch in an operating system?

An event interrupt Signup and view all the answers

Which of the following states indicates that a process has finished its execution?

Terminated Signup and view all the answers

What is NOT a reason for a process to enter the terminated state?

Long-term scheduling Signup and view all the answers

Which option correctly explains the 'Suspend Ready' state?

A process is in memory but not currently using the CPU due to resource limitations. Signup and view all the answers

Study Notes

Operating Systems - Unit 05

Operating System Classification:
- Single user - single task: One user, one task at a time.
- Single user - multi-task: One user, multiple tasks simultaneously.
- Multi-user - multi-task: Multiple users, multiple tasks simultaneously.
- Multi-threading: Improves application performance by allowing parallel execution of sub-processes.
- Real-time: Designed for highly reliable applications requiring precise timing, crucial in safety-critical situations.
- Time-sharing: Enables multiple programs/users to share the processor (CPU) time, ensuring fast response times and reducing CPU idleness.
- Multiprogramming: Allows multiple programs to be loaded into memory and executed concurrently by sharing CPU time.
- Multitasking: Enables concurrent execution of multiple tasks.
File Systems:
- FAT (File Allocation Table): Supports various devices and includes features like encryption, recovery, and compression.
- NTFS (New Technology File System): Supports advanced features such as encryption, recovery, and compression.
- Fragmentation (Internal/External): Issues that arise when allocated disk space is not completely contiguous for the file. Internal fragmentation is when the allocated space has unused portions, and external fragmentation is when sufficient contiguous space exists but isn't available.
Storage Allocation:
- Contiguous Allocation: Allocates disk space in contiguous blocks, simple but susceptible to fragmentation and doesn't easily extend files.
- Linked Allocation: Each block in a file points to the next, allowing easy file growth but requiring multiple seeks to access the file.
- Indexed Allocation: Uses a table of pointers (index block) for fast access, eliminating external fragmentation.
Disk Formatting:
- Low-level Formatting: Low-level formatting physically marks the cylinders and tracks of a hard disk.
- Partitioning: Divides the hard disk into regions (partitions) for better organization and management.
- High-level Formatting: Creates and configures a file system on a hard disk partition.
Process Management:
- Process Control Block (PCB): A data structure maintained by the OS for each process, containing essential information like Process ID (PID), state, CPU registers, I/O status, and memory management details.
- Process States: Processes go through different states (new, ready, running, wait/blocked, terminated, suspend/wait, suspend/ready) during execution.
Scheduling Policies:
- Non-preemptive: A running process continues until it terminates, blocks, or changes to another state.
- Preemptive: A running process may be interrupted by the OS for certain reasons, like timing or priority.
Context Switching:
- Used by the OS to switch between processes.
Interrupts: Events that cause a change in the order of process execution.
Process Scheduling:
- Long-term Scheduling (Job Scheduling): Controls the process rate admitted into the system.
- Medium-term Scheduling: Handles swapping of processes between memory and storage when needed.
- Short-term Scheduling (CPU Scheduling): Selects and allocates the CPU to a ready process.
Times Related (Processes):
- Waiting Time: Time a process waits in a queue to get the CPU.
- Arrival Time: When a process enters the ready queue.
- Burst Time: Time needed to execute a process in the CPU.
- Completion Time: Time a process finishes.
- Turnaround Time: Total time from submission to completion of a process.
- Response Time: Time taken between arrival and obtaining the CPU.
- Throughput: Number of processes completed in a unit of time.

Memory Management

Memory Management Unit (MMU): Converts virtual addresses to physical addresses.
Paging: Divides memory into fixed-size blocks (pages) for efficient allocation and management.
Logical Address: Address of a data element as seen by a program.
Physical Address: Actual address in RAM.
Page Table: A table that maps virtual pages to physical frames.
Virtual Memory: Allows running programs larger than available physical memory, using secondary storage for parts.
Page Fault: An event when a program tries to access a page not in RAM, requiring retrieval from secondary storage.

Device Management

Spooling: A technique to buffer I/O operations to improve performance.
Buffering: A technique to store data temporarily before processing or transferring.
Caching: A fast access storage to reduce access time.
Device Drivers: Software that enables interaction between the computer and peripheral devices.

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Description

Explore the key concepts of operating systems in Unit 05, including classifications such as single user and multi-user systems, multitasking, and real-time operations. Additionally, gain insights into various file systems like FAT and their functionalities. Test your knowledge and comprehension of these vital topics within operating systems.