BSC CSIT Semester 4 – Operating System () Questions & Answers | Past TU Exam Papers

- Parallelism: Multiple cores execute threads simultaneously → higher throughput. - Overlap I/O and CPU: While one thread blocks on I/O, another runs → better CPU utilization. - Responsiveness: GU

- Semaphores provide minimal, powerful primitives (P/wait, V/signal). - Critical sections: Protect shared data; without semaphores, races corrupt state. - Ordering: Counting semaphores model bound

Thread-Based Execution and Multithreading Models 1. How Thread-Based Execution Minimizes Context Switching - Definition of Thread: A thread is the smallest unit of CPU execution within a process. Mul

Process State Transitions | Transition | Possible? | Example / Explanation | |--------------------|-----------|---------------------| | Running → Ready | Yes | Preemption by scheduler:

(a) What is a Race Condition? A race condition occurs in a multi-process or multi-threaded environment when two or more processes access and modify shared data simultaneously, and the final outcome de

Difference Between Program and Process | Program | Process | |-------------|--------------| | A program is a set of instructions written to perform a specific task. | A process is a program in executi

How Multithreading Improves Performance Over Single-Threaded Solutions 1. Definition: - Single-threaded program: Executes one task at a time within a single process. - Multithreaded program: Divides a

Peterson’s Solution for Mutual Exclusion 1. Definition: Peterson’s solution is a classical software-based algorithm used to ensure mutual exclusion between two processes accessing a critical section (

Interactive System Goals Interactive systems focus on fast response to users. Major goals are: - Fast Response Time: System should respond quickly to user actions. - Fairness: Each user/process gets a

When Threads Are Better Than Processes Threads are preferred over processes in situations where tasks need to run simultaneously within the same application. They are better when: - Faster Context Swi

Problems Associated with Semaphores Semaphores are powerful synchronization tools, but they have some drawbacks: 1. Complex to Use Correctly Programmers must manually use wait() and signal() in t

Sleep and Wakeup Mechanism for Mutual Exclusion 1. Concept: - The sleep and wakeup mechanism is a software-based way to achieve mutual exclusion without busy waiting. - Idea: - If a process cann

Lock Variable 1. Definition: - A lock variable is a shared boolean variable used to achieve mutual exclusion between processes in a critical section. - Purpose: Ensure that only one process enters t

SJF and SRTN Scheduling Algorithms 1. Shortest Job First (SJF) Scheduling - Type: Non-preemptive - Concept: - Among the available processes, select the one with the shortest burst (execution) ti

1. Why Process Scheduling is Needed - The CPU is a shared resource among multiple processes. - Scheduling ensures: 1. Efficient CPU utilization 2. Fairness among processes 3. Reduced wai

1. System Call Definition: A system call is a request made by a user-level program to the operating system (kernel) to perform operations that cannot be done directly by the program, such as: - File

Lock Variable in Achieving Mutual Exclusion 1. Concept A lock variable is a shared boolean variable used to control access to a critical section (CS). - lock = 0 → critical section is free - lock

Sleeping Barber Problem 1. Introduction The Sleeping Barber Problem is a classical process synchronization problem introduced by Dijkstra. It demonstrates how to handle synchronization between mult

Semaphore and Critical Section (5 Marks) A semaphore is a synchronization tool used in operating systems to control access to the critical section and avoid race conditions. It ensures that only one p

Priority Scheduling (Non-preemptive) — Calculation Assumption: Non-preemptive priority scheduling (priority 1 = highest). If a process is running it is not preempted by a newly arrived higher priori