Operating Systems Overview and Concepts

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Questions and Answers

What is the primary purpose of virtual memory?

  • To allow programs to use more memory than physically available RAM by using disk space (correct)
  • To increase the physical RAM available to the CPU
  • To directly access data on the hard drive faster
  • To manage cache memory more efficiently

Which of the following best describes a primary difference between paging and segmentation?

  • Paging divides memory into variable-sized blocks while segmentation uses fixed-size blocks.
  • Segmentation is faster, whereas paging is slower due to address translation overhead.
  • Paging is a software technique and segmentation is a hardware based technique.
  • Paging divides memory into fixed-size blocks while segmentation uses variable-sized blocks. (correct)

Which of the following is NOT a typical method for Inter-Process Communication (IPC)?

  • Message Queues
  • Semaphores
  • Direct Memory Access (DMA) (correct)
  • Shared Memory

What is a key disadvantage of using a linear list for directory implementation?

<p>It leads to slower search times as directory size increases. (A)</p> Signup and view all the answers

Which of these best describes the function of a 'channel' in the context of device management?

<p>A dedicated communication path between I/O devices and memory. (C)</p> Signup and view all the answers

Which component of an operating system acts as an interface between the user and the system kernel?

<p>Shell (C)</p> Signup and view all the answers

Which of the following is NOT a typical function of an operating system?

<p>Direct Hardware Manipulation (B)</p> Signup and view all the answers

What is the primary purpose of the Process Control Block (PCB)?

<p>To store the current state and context of a process (B)</p> Signup and view all the answers

Which scheduling algorithm can potentially lead to 'starvation'?

<p>Priority Scheduling (D)</p> Signup and view all the answers

In memory management, what does the term 'fragmentation' refer to?

<p>Unused memory space that is too small to allocate to a process (D)</p> Signup and view all the answers

What is the primary concept behind virtual memory?

<p>To expand the amount of usable memory space beyond the physical memory available (A)</p> Signup and view all the answers

What is the purpose of a 'semaphore' in process synchronisation?

<p>To prevent a process from entering a critical section (B)</p> Signup and view all the answers

Which memory management technique might employ page tables?

<p>Paging (C)</p> Signup and view all the answers

Flashcards

What is an operating system?

An operating system (OS) is a software layer that manages computer hardware and provides basic services to applications. It acts as a bridge between the hardware and software, allowing users to interact with the computer efficiently.

What is the kernel in an operating system?

The kernel is the core of an operating system, responsible for fundamental tasks like memory management, process scheduling, and handling hardware interactions. It sits at the heart of the OS, providing a foundation for all other functionalities.

What is a process in an operating system?

A process is an instance of a running program. It encompasses the program's code, data, and resources it uses. Think of it as a separate, independent execution environment within the operating system.

What are threads in an operating system?

Threads are lightweight units of execution within a process. They share the process's resources but can be controlled independently. In a way, they're like smaller tasks within a larger program.

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What is memory management in an operating system?

Memory management involves allocating and managing computer memory efficiently. This includes allocating memory for processes, swapping data between RAM and disk, and preventing memory conflicts.

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What is a file system in an operating system?

A file system is a hierarchical structure used to organize and store files on a storage device. It defines rules for how data is stored, accessed, and managed. Think of it as a directory structure for your computer's files.

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Paging

A memory management technique where the physical memory is divided into fixed-size blocks called frames, and the logical address space is divided into pages of the same size. When a process needs to access a page, the operating system maps the virtual address to the physical address in the corresponding frame.

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Segmentation

A memory management technique where the logical address space is divided into variable-sized segments. Each segment corresponds to a logical unit of the program, such as a code segment, data segment, or stack segment. The operating system maps the virtual addresses to the physical memory addresses within the corresponding segments.

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Segmentation with paging

A technique that combines both paging and segmentation. The logical address space is divided into segments, and each segment is further divided into pages. When a process needs to access a page within a segment, the operating system locates the corresponding frame in physical memory, using both the segment and page information.

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Pipes

A method of inter-process communication (IPC) where data is transferred between processes through a unidirectional pipe. Data flows from the writing process to the reading process without any backflow. Often used for simple communication between related processes.

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Message Queues

A specialized data structure that allows processes to communicate by exchanging messages. Each message queue has a unique identifier and is associated with a specific process. A message queue can store a sequence of messages, and processes can either send messages to or receive messages from a queue.

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Study Notes

Course Overview and Objectives

  • Understand the concept of system and its processes

Course Outcomes

  • Students will be able to describe basic components of an operating system in general purpose, real-time, and embedded applications
  • Define processes, threads, asynchronous signals, and competitive system resource location
  • Explain multi-tasking and standard scheduling algorithms
  • Give an overview of system memory management
  • Explain file system implementation

Course Outline

  • Unit 1 (OS concepts): 6 hours
  • Unit 2 (Process management): 5 hours
  • Unit 3 (Memory management): 6 hours
  • Unit 4 (Inter-process communication): 7 hours
  • Unit 5 (Information management): 7 hours

Detailed Syllabus:

  • Unit 1: Introduction to OS concepts, evolution of OS structures (kernel, shell), general structure of MSDOS and Windows 2000, comparison of ANSI C and C++, need for an operating system, layered architecture/logical structure, types of OS, resource management, virtual machines, OS services, BIOS, system calls/monitor calls, firmware-BIOS, boot strap loader
  • Unit 2: Process management, process and threads, process states, process control block, process scheduling, preemptive and non-preemptive scheduling, dispatcher, scheduling criteria, concurrent/co-operating processes, precedence graph, critical section problem, two-process solution, synchronization hardware, semaphores, deadlock detection/handling/prevention/avoidance, starvation, critical regions, monitors, inter-process communication
  • Unit 3: Memory management, objectives and functions, simple resident monitor program, overlays, swapping, schemes, paging (simple, multi-level), internal/external fragmentation, virtual memory concept, demand paging, page interrupt fault, page replacement algorithms, segmentation (simple, multi-level, segmentation with paging), cache memory
  • Unit 4: Inter-process communication, virtual memory, concept, virtual address space, paging schematics, pure segmentation, segmentation with paging, hardware support and implementation details, memory fragments, overview of IPC methods, pipes, popen, pclose functions, co-processes, FIFOs, system V IPC, message queues, semaphores, inter-process communication, shared memory, client-server properties, stream pipes, passing file descriptors, and an open server-version 1, client-server connections functions
  • Unit 5: Information management, files and directories, directory structure, directory implementation (linear lists, hash tables), device management (dedicated, shared, virtual devices), serial access devices, direct access devices, direct access storage devices, channels and control units, disk scheduling methods

Textbooks and Reference Books

  • Operating Systems Concepts by Silberschatz, Galvin (2008)
  • Modern Operating Systems by Tenenbaum (2005)
  • Operating Systems by William Stallings (2002)
  • UNIX System Programming by Terrence Chan (1999)
  • Advanced Programming in UNIX Environment by W. Richard Stevens (2005)

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PGCSA102: Operating Systems PDF

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