Unit 1: Introduction to Operating Systems

Which of the following is NOT a function of an operating system?

1. Process Management
2. Memory Management
3. Compiler Design
4. File Management

The mode bit value in kernel mode is:

1. 1
2. 0
3. -1
4. Depends on OS

Which system call is used to create a new process in Unix/Linux?

1. exec()
2. fork()
3. wait()
4. kill()

RTOS stands for:

1. Rapid Transaction Operating System
2. Real-Time Operating System
3. Remote Terminal Operating System
4. Reduced Time Operating System

In a layered OS architecture, the hardware is at:

1. The topmost layer
2. Layer 0 (innermost)
3. The middle layer
4. Outside all layers

Why does the OS need two separate modes (kernel and user)?

1. To make the computer faster
2. To prevent user programs from directly accessing hardware and crashing the system
3. To support multiple languages
4. To reduce electricity consumption

Explain why multiprogramming increases CPU utilization:

1. It makes the CPU faster
2. When one process waits for I/O, the CPU switches to another process instead of sitting idle
3. It adds more CPUs
4. It reduces the number of processes

How does a microkernel architecture improve system stability?

1. By running everything in kernel mode
2. By running device drivers and file systems in user space — if they crash, the kernel survives
3. By disabling all hardware access
4. By removing the file system entirely

What is the role of a system call in the OS?

1. It directly executes hardware instructions
2. It provides a controlled interface for user programs to request kernel services
3. It is a programming language function
4. It is used only by administrators

Distinguish between a program and a process:

1. They are the same thing
2. A program is a passive entity (code on disk); a process is an active entity (program in execution with resources)
3. A process is always smaller than a program
4. Programs run in kernel mode, processes in user mode

You run strace ls on a Linux system and see 87 lines of output. What does this indicate?

1. The ls command has 87 bugs
2. The ls command makes approximately 87 system calls to list directory contents
3. The system has 87 files
4. The kernel version is 87

IRCTC's Tatkal system needs to handle 12 lakh concurrent users with guaranteed response time. Which OS type is most appropriate?

1. Simple Batch OS
2. Distributed + Real-Time hybrid
3. Single-user desktop OS
4. MS-DOS

A student writes a C program that calls fork(). How many processes exist after the call?

1. 1
2. 2
3. 3
4. 0

You see load average: 8.5, 7.2, 6.1 in top on a 4-core server. What does this tell you?

1. The server is healthy
2. The server is overloaded — load average should ideally be ≤ number of cores (4)
3. The server has 8 CPUs
4. The server needs more RAM

Which Linux command shows the kernel version you're running?

1. ls -version
2. uname -r
3. kernel --show
4. cat /etc/os

Compare monolithic and microkernel architectures. Which would you recommend for ISRO's satellite OS and why?

1. Monolithic — faster performance, critical for real-time satellite operations
2. Microkernel — stability is more important; a driver crash shouldn't kill the satellite
3. Neither — satellites don't use OS
4. Both are identical for embedded systems

Analyze why 96.3% of the world's supercomputers run Linux (monolithic) rather than a microkernel OS:

1. Linux is free
2. Supercomputers need maximum performance — monolithic kernels avoid user↔kernel message-passing overhead critical for HPC workloads
3. Microkernel doesn't support multitasking
4. Linux was invented first

Differentiate between multiprogramming and multitasking:

1. They are identical
2. Multiprogramming switches on I/O wait (no time slice); multitasking uses time slicing for rapid CPU sharing
3. Multitasking is slower than multiprogramming
4. Multiprogramming requires multiple CPUs

Examine why Android uses a modified Linux kernel rather than building a new OS from scratch:

1. Google was lazy
2. Linux provides a mature, tested kernel with hardware driver support for thousands of devices, saving years of development
3. Android doesn't use Linux
4. Linux was the only option available

Compare system calls and library functions. Why is printf() not a system call but write() is?

1. printf() doesn't produce output
2. printf() is a C library function that internally calls write() (which is the actual system call that switches to kernel mode)
3. write() is slower than printf()
4. They are both system calls

IRCTC chose Linux over Windows for production servers. Evaluate this decision:

1. Poor decision — Windows is more user-friendly
2. Good decision — Linux is free (reduces cost for govt), open-source (auditable), more stable for high-concurrency, and runs 96% of web servers globally
3. Irrelevant — OS doesn't matter for web servers
4. Bad decision — Linux has no GUI

A startup CEO says: "We don't need to understand OS — we just use cloud." Critique this statement:

1. Correct — cloud abstracts everything
2. Incorrect — cloud VMs still run Linux/Windows. Understanding OS helps optimize costs, debug performance issues, and configure servers properly
3. Partially correct for frontend developers only
4. Correct if using serverless exclusively

Evaluate whether India should develop its own indigenous OS (like BharOS) or continue using Linux/Android:

1. Build from scratch — national security requires it
2. Continue using Linux — it's open-source, globally maintained, and building from scratch is prohibitively expensive. Customize Linux (like Android did) for Indian needs instead
3. Use Windows only
4. OS is irrelevant in the cloud era

Judge the tradeoff: "A monolithic kernel is faster but less stable. A microkernel is stable but slower." Is this always true?

1. Yes, always
2. Generally true, but modern hybrid approaches (Linux loadable modules) combine speed with modularity, partially mitigating both downsides
3. No — microkernels are always faster
4. No — monolithic kernels never crash

Assess the risk: Zerodha's trading platform MUST execute stock orders within 10 microseconds. Which OS failure would be most catastrophic?

1. File system corruption
2. Unpredictable scheduling latency — if the OS schedules another process during a trade execution, the order may miss the price window
3. Slow boot time
4. Poor GUI rendering

Design an OS architecture for India's Aadhaar authentication system (1.4 billion users, biometric data, real-time response needed). Which architecture would you propose?

1. Single monolithic OS on one server
2. Distributed OS with microkernel nodes — biometric processing in real-time, fault-tolerant across multiple data centres, with hardware-isolated security domains
3. MS-DOS on each terminal
4. Any general-purpose desktop OS

Propose a system call interface for a new Indian government document management OS. Which categories of system calls are essential?

1. Only file management calls
2. Process control (handle multiple users), file management (create/read/write documents), security (authentication, access control), communication (inter-department IPC), and device management (printers, scanners)
3. Only networking calls
4. No system calls needed — user programs access hardware directly

Design a sysinfo monitoring script. Which system information should it collect for a production server health check?

1. Only the hostname
2. CPU load, memory usage (used/free/swap), disk space, running processes, network connections, uptime, kernel version, and top 5 resource consumers
3. Only the current time
4. The colour of the terminal

Create a comparison framework for evaluating OS choices for an Indian EdTech startup building a live-streaming platform:

1. Just pick the cheapest OS
2. Evaluate on: licensing cost (Linux=₹0 vs Windows=₹₹₹), concurrency handling (Linux superior for I/O), community support, streaming library compatibility, cloud provider support, and DevOps tooling ecosystem
3. Use whatever the founder's laptop runs
4. OS doesn't matter for streaming

Build a proposal for upgrading a legacy Indian bank's OS infrastructure from Windows Server 2008 to a modern platform. What steps would you include?

1. Just install Windows 11 on all servers
2. Audit current workloads → evaluate Linux vs Windows Server 2022 → pilot migration on non-critical systems → train staff on new OS → phased rollout → security hardening → monitoring setup → document everything
3. No upgrade needed — if it works, don't fix it
4. Replace all servers with mobile phones