Question paper of Operating System Diploma in Computer Engineering 5th semester
Operating System Question Paper 2075
Applied Operating System Question Paper 2073
Question solution of Operating System diploma in computer
1. Describe the operating system. Explain OS as a Virtual Machine and resource manager.
Operating System (OS):
An operating system is software that acts as an intermediary between computer hardware and the user/application software. Its primary functions include managing hardware resources, providing a user interface, and facilitating the execution of programs. The OS plays a crucial role in coordinating and controlling the overall operation of a computer system.
OS as a Virtual Machine:
The concept of an operating system as a virtual machine refers to the abstraction of hardware resources to create a virtualized environment for applications to run. The OS provides a virtual machine interface to applications, allowing them to interact with a standardized set of resources without needing to be aware of the underlying hardware details.
In this context:
Abstraction Layer: The OS creates an abstraction layer between the application software and the hardware, presenting a virtualized version of the machine to applications.
Resource Virtualization: The OS virtualizes hardware resources, such as the CPU, memory, and storage, allowing multiple applications to share and use these resources concurrently.
Isolation: Applications operate in isolated environments, unaware of the activities of other applications. This isolation enhances security and stability.
OS as a Resource Manager:
The operating system acts as a resource manager, overseeing the allocation and utilization of various hardware resources. Key aspects include:
- Memory Management: The OS manages the allocation and deallocation of memory to programs, ensuring efficient utilization and preventing conflicts between different applications.
- Processor (CPU) Management: It schedules processes, allocating CPU time to different tasks, and ensuring fair and efficient execution.
- Device Management: The OS controls communication between software and peripheral devices, handling input and output operations.
- File System Management: The OS manages file storage, organizing and providing access to data on storage devices.
- Security and Access Control: It enforces security policies, controls user access, and protects the system from unauthorized activities.
- Task Scheduling: The OS determines the order and priority of tasks, optimizing the utilization of resources and ensuring responsive system performance.
2. Differentiate between process and threads. explain Dekker's algorithm.
Differentiate between process and Threads are given below:
Process:
- A process is an independent program in execution, with its own memory space, resources, and state.
- Processes are isolated from each other and communicate through inter-process communication mechanisms.
- Creation and termination of processes are more resource-intensive, as each process has its own memory space.
Thread:
- A thread is a lightweight unit of execution within a process. Multiple threads within a process share the same memory space and resources.
- Threads within the same process can communicate directly through shared memory.
- Threads are more lightweight compared to processes, and the creation and termination of threads are less resource-intensive.
Dekker's Algorithm:
Dekker's Algorithm is a synchronization algorithm designed to achieve mutual exclusion in a shared-memory environment, allowing multiple processes or threads to coordinate and avoid conflicts when accessing shared resources. It was proposed by Dutch mathematician and computer scientist Th. J. Dekker.
The algorithm ensures that only one process or thread can enter the critical section at a time. Here is a simple explanation of the algorithm for two processes (P0 and P1) competing for access to a critical section:
Flags: Each process has its flag variable, initially set to false, indicating that the process is not in the critical section.
Turn Variable: A turn variable is used to determine which process can enter the critical section. It is initially set to 0.
Process Code:
Process P0:
- Set its flag to true.
- Wait until P1's turn (turn variable is 1) and P1's flag is false.
- Enter the critical section.
- Set its flag to false.
- Set the turn variable to 1.
Process P1:
- Set its flag to true.
- Wait until P0's turn (turn variable is 0) and P0's flag is false.
- Enter the critical section.
- Set its flag to false.
- Set the turn variable to 0.
Explanation:
- The algorithm ensures mutual exclusion by checking the flags and turning variables before entering the critical section.
- If a process is not in the critical section (flag is false), and it is the turn of the other process (turn variable), it can enter the critical section.
- The algorithm avoids deadlock and ensures progress, but it may suffer from the problem of busy waiting.
3. Explain virtual exclusion, context switching, critical section, and race condition with an example
Sure, let's break down these concepts:
1. Mutual Exclusion:
Mutual exclusion is a fundamental concept in concurrent programming, ensuring that only one process or thread can execute a critical section at a time. It prevents multiple processes from simultaneously accessing shared resources, avoiding conflicts and ensuring data consistency.
Example of Mutual Exclusion:
Consider two processes, P1 and P2, sharing a printer. To implement mutual exclusion, a lock mechanism is used. Before accessing the printer, a process must acquire the lock. If P1 has the lock, P2 is prevented from accessing the printer until P1 releases the lock after completing its task.
2. Context Switching:
Context switching is the process of saving the state of a currently running process or thread, and then restoring the state of another process or thread to continue its execution. It occurs when the operating system switches the CPU from one task to another.
Example of Context Switching:
Imagine a multitasking operating system running multiple applications. The CPU may execute process A for a certain time, save its state, switch to process B, and then later switch back to process A. Context switching allows multiple tasks to share the CPU, providing the illusion of parallel execution.
3. Critical Section:
A critical section is a part of a program where shared resources are accessed, and concurrent access must be controlled to maintain data integrity. Only one process or thread is allowed to execute the critical section at any given time.
Example of Critical Section:
Consider a scenario where multiple threads are updating a shared counter variable. The critical section includes the code that increments the counter. To maintain data consistency, a synchronization mechanism like locks or semaphores is used to ensure that only one thread at a time can execute the critical section.
4. Race Condition:
A race condition occurs when the behavior of a program depends on the relative timing of events, and the outcome is unpredictable or unintended due to the interleaving of multiple threads or processes.
Example of Race Condition:
Suppose two threads, A and B, are incrementing a shared variable. Without proper synchronization, a race condition may occur. If both threads read the variable, increment it, and then write the result back without coordination, the final value may not reflect the expected sum of increments. The result depends on the interleaving of the individual instructions of both threads.
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