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.)
