(SEM IV) THEORY EXAMINATION 2017-18 OPERATING SYSTEM

The B.Tech Operating System (RCS401) question paper from the 2017–18 IV Semester Theory Examination is a 70-mark, 3-hour analytical examination designed to assess a student’s conceptual understanding and practical problem-solving abilities in the domain of operating systems. The paper includes questions on CPU scheduling, process synchronization, memory management, deadlock handling, page replacement, file allocation methods, and disk scheduling. It is divided into three structured sections, each testing different cognitive levels—from definitions to numericals to system-level analysis. 

SECTION A – Foundational Concepts (Short Answers, 14 Marks)

This section contains 7 short-answer questions, each worth 2 marks, covering essential OS fundamentals such as:

Definition and objectives of an Operating System

CPU Scheduling criteria (CPU utilization, throughput, waiting time, etc.)

Interprocess communication & context switching

Internal vs. External fragmentation

Disadvantages of single contiguous memory allocation

Wait-for graph usage in deadlock detection

Busy waiting and how semaphores eliminate it

These questions ensure students understand basic OS mechanisms and terminology.
 

SECTION B – Intermediate-Level Analytical Questions (Any 3 × 7 = 21 Marks)

This section requires deeper explanation, diagrams, algorithms, and system analysis.

1. Layered OS Structure with Protection & Security

Students explain the layered architecture, neatly illustrated with diagrams, along with:

Need for abstraction layers

Security features

Protection rings

2. Dining Philosophers Problem (Using Monitors)

A conceptual synchronization problem requiring understanding of monitors, condition variables, and deadlock avoidance.

3. Banker's Algorithm (Safety & Need Matrix)

A table of allocated, maximum, and available resources is shown on Page 1, and students must compute:

Need matrix

Safe sequence using Banker’s algorithm
 

4. Optimal Page Replacement (Three Frames)

Given a reference string:
1, 2, 3, 4, 2, 1, 5, 6, 2, 1, 2, 3, 7, 6, 3, 2, 1, 2, 3, 6,
students calculate the number of page faults using Optimal Replacement, assuming:

Three empty frames

Stack-based replacement model

5. Deadlock With a Single Process

Conceptual explanation on whether a single process can cause deadlock and under what scenario.

SECTION C – Advanced OS Problems & Numerical Analysis (5 × 7 Marks)

This section includes computational problems, complex system comparisons, and memory/file management concepts.

Q3 – OS Components & System Types

Students choose one:

OS components (File system, memory manager, process manager, device manager, etc.)

Difference between:

Interactive vs. Batch systems

Multiprogramming vs. Time-sharing systems
 

Q4 – Critical Section & Mutual Exclusion

Implementation of test-and-set instruction for mutual exclusion
OR

Software-based solution to critical section problem
(Peterson’s solution or Bakery Algorithm)

Q5 – CPU Scheduling Problems

This part contains numerical and Gantt chart–based scheduling questions using arrival time and burst time tables on Page 2.

Students must compute:

Gantt charts

Average waiting time

Average turnaround time

Scheduling methods:

FCFS & SRTF (first table on Page 2)

SRTF & Round Robin (quantum = 3) (second table)

Q6 – Paging & Thrashing Concepts

Belady’s Anomaly, affected algorithms (FIFO) and how to avoid it
OR

Thrashing:

Causes

Detection

Working Set Model

Page Fault Frequency (PFF) control

Q7 – File Allocation & Disk Management

Students explain:

Linked allocation

Contiguous allocation

Indexed & multi-level indexed allocation

And determine which method minimizes directory space (Indexed allocation).

Or write short notes on:

I/O buffering

Disk storage & disk scheduling (FCFS, SSTF, SCAN, C-SCAN, etc.)