BCA DCA2108 OPERATING SYSTEMS

Description

SESSION	SEP 2025
PROGRAM	BACHELORS OF COMPUTER APPLICATIONS (BCA)
SEMESTER	III
COURSE CODE & NAME	DCA2108 OPERATING SYSTEMS

 

 

Set-I

 

Q1. What is a PCB? What all information is stored in a PCB. 5+5        

Ans 1.

PCB

A Process Control Block (PCB) is a crucial data structure maintained by the Operating System (OS) to manage and monitor processes effectively. It acts as the identity card of a process, containing all necessary information about its current state and attributes. When a process is created, the operating system generates a PCB for it, and when the process terminates, its PCB is destroyed. The PCB allows the OS to keep track of the execution status of each process, ensuring proper scheduling, execution, and resource management.

Each process in the system has its own unique PCB, which is stored in the operating system’s memory, usually in the kernel

 

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Q2. What is Inter-Process Communication (IPC) and why is it important? 5+5           

Ans 2.

Inter-Process Communication (IPC)

Inter-Process Communication (IPC) is a mechanism that allows processes to communicate and coordinate with each other while executing independently in a multitasking operating system. Since each process operates in its own address space and cannot directly access another process’s data, IPC provides the tools and methods for data exchange and synchronization between them. It is particularly crucial in systems where multiple processes need to work collaboratively, such as client-server applications, distributed systems, and multi-core processors.

IPC enables processes to share information, signals, and synchronization objects without interference. It provides controlled communication channels that ensure data consistency and prevent race condition

 

Q3. Explain the differences between SJF, and Round Robin scheduling in detail, taking suitable examples. 5+5           

Ans 3.

Scheduling Algorithms

CPU scheduling is the process of selecting one process from the ready queue for execution. It determines the order in which processes access the CPU, directly affecting system efficiency and responsiveness. Two widely used algorithms are Shortest Job First (SJF) and Round Robin (RR) scheduling, each with its own advantages and trade-offs.

Shortest Job First (SJF) scheduling selects the process with the smallest CPU burst time first. The idea is to minimize average waiting time by executing shorter tasks before longer ones. SJF can be preemptive or non-preemptive. In non-preemptive SJF, once a process starts, it runs to completion. In preemptive SJF, also called Shortest Remaining Time First (SRTF), the CPU is preempted if a new

 

Set-II

Q4. Discuss Bankers Algorithm in detail. 10         

Ans 4.

The Banker’s Algorithm is a classical deadlock-avoidance algorithm proposed by Edsger Dijkstra. It ensures that a system never enters an unsafe state by carefully examining resource-allocation requests before granting them. The name derives from the analogy of a banker who never allocates more loans than what can be safely repaid by customers. In an operating system, processes are treated like customers, and system resources—such as CPU cycles, memory blocks, or I/O devices—are treated like loans. The algorithm checks whether fulfilling a resource request would still leave enough resources for all other processes to finish eventually. If yes, the request is approved; if not, the process

 

 

Q5. What are the deadlock avoidance and recovery measures taken by the OS? Discuss in detail. 5+5         

Ans 5.

Deadlock Avoidance

Deadlock avoidance ensures that the operating system never enters a state where deadlock could occur. Unlike prevention, which restricts resource usage, avoidance dynamically analyzes every allocation request using information about future needs. The OS allocates a resource only if it will keep the system in a safe state. Algorithms like Banker’s Algorithm and Safe State Detection belong to this category.

Avoidance relies on the four Coffman conditions—mutual exclusion, hold-and-wait, no pre-emption, and circular wait—and ensures that not all of them hold simultaneously. For example, by pre-empting resources or by requiring processes to declare maximum resource requirements in advance, the OS can predict potential circular waits. Resource-allocation graphs with claim edges help determine

 

Q6. What are the primary sources of I/O overhead in demand paging, and how do they impact overall system performance? Suggest methods to mitigate these overhead.         10       

Ans 6.

I/O Overhead in Demand Paging and Its Impact on System Performance

Sources of I/O Overhead

Demand paging is a virtual-memory technique where pages are loaded into physical memory only when required by a process. Although it saves memory space, it introduces input/output (I/O) overheads that affect overall performance. The main sources of overhead include page faults, swap-space access, and secondary-storage latency.

When a page fault occurs, the OS must locate the missing page on the disk, read it into an available frame, and update the page table. This disk access involves mechanical seek and rotational delays, which are much