Course Code BCA 301 L T C

Course Name: Operating System & Linux Programming 3 1 4

INSTRUCTIONSTOPAPERSETTERS:

1. Question No. 1 should be compulsory and cover the entire syllabus. There should be10 questions of short answer type of 2.5 marks each, having at least 2 questions from each unit.

2. Apart from Question No. 1, rest of the paper shall consist of four units as per the syllabus. Every unit should have two questions to evaluate analytical/technical skills of candidate. However, student may be asked to attempt only 1 question from each unit. Each Question should be of12.5 marks, including its subparts, if any.

3. Examiners are requested to go through the Course Outcomes (CO) of this course and prepare the question paper accordingly, using Bloom’s Taxonomy (BT), in such a way that every question be mapped to some or other CO and all the questions, put together, must be able to achieve the mapping to all the CO(s), in balanced way.

LEARNING OBJECTIVES:

In this course, the learners will be able to develop expertise related to the following:-

1. Working and functionalities of operating system

2. Understand the concept of process scheduling, ,memory management, deadlock and file system

3. Understand basic commands of Linux and shell scripts.

PRE-REQUISITES:

1. Basic understanding of hardware and software of computer organization.

COURSE OUTCOMES (COs):

After completion of this course, the learners will be able to:-

Understand the basic concept of Operating System with the help of Unix and Linux Architecture.
Understand the concept of Processes, Process Scheduling, Process Synchronization and applying process commands in Linux environment.
Understand the concept of memory management and deadlock.
Understand the concept of file Systems, Types and Access Methods by using Linux commands.

UNIT–I

No. of Hours: 12 Chapter/Book Reference: TB1 [Chapter 1]; TB2 [Chapters 1, 2, 3, 4, 5]
Introduction: What is an Operating System, Functions of Operating System, Simple Batch Systems; Multi programmed Batch systems, Time-Sharing Systems, Personal-computer systems, Parallel systems, Distributed Systems, Real-Time Systems.
Introduction to Linux: Architecture of Linux OS, Basic directory structure of Linux, Basic commands of Linux:-man,info,help,whatis,apropos, basic directory navigation commands likecat,mkdir,rmdir ,cd, mv, cp, rm, ,file, pwd ,date,cal,echo,bc,ls,who,whoami,hostname,uname,tty,aliase
Vi Editor:vi basics, Three modes of vi Editor, how to write, save, execute a shell script in vi editor

UNIT–II

No. of Hours: 12 Chapter/Book Reference: TB1 [Chapters 3, 5, 6]; TB2 [Chapter 9]
Processes: Process Concept, Process Scheduling, Operation on Processes
CPU Scheduling: Basic Concepts, Scheduling Criteria, Scheduling Algorithms
Process Synchronization: Background, The Critical-Section Problem, Semaphores solution to critical section problem
Process related commands in Linux: ps, top, pstree, nice, renice and system calls

UNIT–III

No. of Hours: 12 Chapter/Book Reference: TB1 [Chapters 7, 8, 9]
Memory Management: Background, Logical versus Physical Address space, swapping, Contiguous allocation, Segmentation, Paging
Virtual Memory: Demand Paging, Performance of Demand Paging, Page Replacement, Page-replacement Algorithms, Allocation of Frames, Thrashing
Deadlocks: System Model, Deadlock Characterization, Methods for Handling Deadlocks, Deadlock Prevention, Deadlock Avoidance, Deadlock Detection, Recovery from Deadlock

UNIT–IV

No. of Hours: 10 Chapter/Book Reference: TB1 [Chapter 10]; TB2 [Chapter 6]
Information Management: Introduction, File Concept, Access methods, Directory and Disk structure, File Protection
Linux File Security: Permission types, Examining permissions, changing permissions (symbolic method numeric method)

TEXT BOOKS:

TB1. Silbersachatz and Galvin, “Operating System Concepts”, John Wiley & Sons, 10 th Ed. 2018
TB2. Sumitabha Das, “Unix Concepts and Application”, TMH
REFERENCE BOOKS:
RB1. Madnick E., Donovan J., “Operating Systems”, Tata McGraw Hill, 2011
RB2. Tannenbaum, “Operating Systems”, PHI, 4th Edition, 2015
RB3. Sivaselvan, Gopalan, “A Beginner’s Guide to UNIX”, PHI Learning

Course Code: BCA 371

Course Name: Practical-X LINUX – OS LAB

LEARNING OBJECTIVES:

In this course, the learners will be able to develop expertise related to:

1. Unix/Linux environment

2. Understanding of Linux commands and scripts

PRE-REQUISITES:

COURSE OUTCOMES (COs):

After completion of this course, the learners will be able to:

Understand Linux Environment with the help of its architecture.
Understand the Linux environment by using general Linux Commands.
Implement Process Related commands.
Implement File Permission concept.
Understanding the shell script by combining commands.

List of Practicals S. No. Detailed Statement Mapping to CO #

Core Practicals

1.Connect to the Linux Server and understand the basic Directory Structure of Linux.

2.To understand help commands like:-man,info,help,whatis,apropos

3.To understand basic directory navigation commands like cat,cd, mv, cp, rm, mkdir,rmdir ,file, pwd command.

4.To understand basic commands like:-date,cal,echo,bc,ls,who,whoami,hostname,uname,tty,aliase

5.To understand vi basics, Three modes of vi Editor, how to write, save, execute a shell script in vi editor.

6.To understand process related commands like: -ps, top, pstree, nice, renice in Linux.

7.To understand how to examine and change File permissions.

8.Set a file to be read-only with the chmod command. Interpret the file permissions displayed by the ls -l command.

9.Delete one or more directories with the rmdir command. See what happens if the directory is not empty. Experiment (carefully!) with the rm -r command to delete a directory and its content.

10.Change your directory to the directory exercises. Create a file in that directory, named the file as example1 using the cat command containing the following text: water, water everywhere and all the boards did shrink; water, water everywhere, no drop to drink.

11.Write basic shell script to display the table of a number.

12.Write basic shell script to input a character from user and then check whether it is uppercase, lowercase or digit.

13.Write basic shell script to calculate factorial of a number.

14.Write basic shell script to input the month number and generate corresponding calendar.

15.Write basic shell script to list all directories.

16.Write basic shell script to display greatest of three numbers.

17.Write basic shell script to check whether the number entered by user is prime or not.

Note:

1. In total 15 practical's to be implemented. 2 additional practical may be given by the course instructor.

2. This is a suggestive list of programs. However, the instructor may add programs as per the requirement of the course.

Hand written Assignment-1

Course Code: BCA 301

Course Name: Operating Systems with Linux


Q1.	Keeping in mind the various definitions of operating system, consider whether the operating system should include applications such as Web browsers and mail programs. Argue both that it should and that it should not, and support your answers.
Q2.	Give two reasons why caches are useful. What problems do they solve? What problems do they cause? If a cache can be made as large as the device for which it is caching (for instance, a cache as large as a disk), why not make it that large and eliminate the device?
Q3.	How could a system be designed to allow a choice of operating systems from which to boot? What would the bootstrap program need to do?
Q4.	Distinguish between: (a) PCS and SCS scheduling, and (b) Preemptive and Non-preemptive scheduling.
Q5.	What resources are used when a thread is created? Provide three programming examples in which multithreading provides better performance than a single-threaded solution.

Assignment-2

Assignment-3

UNIT-I: Introduction to Operating Systems, Linux, and Vi Editor

Part 1: Introduction to Operating Systems (Approx. 5 Hours)

Objective: To understand the fundamental concepts of operating systems, their functions, and various types.

• 1.1 What is an Operating System? (1 Hour)

o Definition and role of an OS.

o Resource management (CPU, Memory, I/O devices).

o User interface.

o Program execution.

o Abstractions provided by the OS.

• 1.2 Functions of an Operating System: (1.5 Hours)

o Process Management: Process creation, termination, scheduling, synchronization, inter-process communication.

o Memory Management: Allocation, deallocation, protection, virtual memory concepts (brief overview).

o File Management: File creation, deletion, organization, access methods, directory structure.

o Device Management: I/O handling, device drivers.

o Security and Protection.

o Error Handling.

• 1.3 Types of Operating Systems: (2.5 Hours)

o Simple Batch Systems:

 Concept and operation.

 Limitations (CPU idle time).

o Multiprogrammed Batch Systems:

 Introduction of multiprogramming.

 CPU utilization improvement.

o Time-Sharing Systems:

 Interactive computing.

 Time slicing and multitasking.

 Response time vs. throughput.

o Personal-Computer Systems:

 Evolution and characteristics.

 User-friendliness.

o Parallel Systems:

 Multiple CPUs/cores.

 Symmetric Multiprocessing (SMP) and Asymmetric Multiprocessing (AMP).

 Benefits (speed, reliability).

o Distributed Systems:

 Networked computers.

 Resource sharing, communication.

 Challenges (coordination, consistency).

o Real-Time Systems:

 Hard vs. Soft real-time.

 Time constraints and determinism.

 Applications (industrial control, robotics).

________________________________________

Part 2: Introduction to Linux (Approx. 5 Hours)

Objective: To gain a basic understanding of the Linux operating system architecture and essential command-line operations.

• 2.1 Architecture of Linux OS: (1 Hour)

o Kernel (monolithic kernel concept).

o Shell.

o User space vs. Kernel space.

o File system.

o Hardware.

• 2.2 Basic Directory Structure of Linux: (1 Hour)

o Root directory (/).

o bin, sbin, etc, home, usr, var, tmp, dev, proc, mnt, media, opt, lib.

o Understanding the purpose of key directories.

• 2.3 Basic Commands of Linux: (3 Hours)

o Help Commands:

 man: Manual pages (e.g., man ls).

 info: GNU info documentation (e.g., info ls).

 help: Shell built-in help (e.g., cd --help).

 whatis: Single-line description (e.g., whatis ls).

 apropos: Search man pages by keyword (e.g., apropos directory).

o Basic Directory Navigation & File Management:

 pwd: Print working directory.

 ls: List directory contents (options: -l, -a, -h, -F).

 cd: Change directory (cd .., cd ~, cd -).

 mkdir: Make directory.

 rmdir: Remove empty directory.

 cat: Concatenate and display file content.

 mv: Move or rename files/directories.

 cp: Copy files/directories.

 rm: Remove files/directories (options: -r, -f).

 file: Determine file type.

o System Information & Utility Commands:

 date: Display or set the system date and time.

 cal: Display a calendar.

 echo: Display a line of text.

 bc: Arbitrary precision calculator language.

 who: Show who is logged on.

 whoami: Print effective userid.

 hostname: Print or set system hostname.

 uname: Print system information (options: -a).

 tty: Print the file name of the terminal connected to standard input.

 alias: Create or display aliases.

________________________________________

Part 3: Vi Editor (Approx. 2 Hours)

Objective: To learn the basics of the Vi text editor, including its modes and how to perform basic file operations and script execution.

• 3.1 Vi Basics: (0.5 Hour)

o Why Vi/Vim is important (ubiquitous, powerful).

o Starting Vi (vi filename).

• 3.2 Three Modes of Vi Editor: (1 Hour)

o Command Mode:

 Navigation (h, j, k, l, w, b, ,,gg,G).∗Deletion(x,dd,dw,d, d^).

 Copying/Pasting (yy, p).

 Undo (u), Redo (Ctrl+r).

o Insert Mode:

 Entering insert mode (i, I, a, A, o, O).

 Typing text.

 Exiting insert mode (Esc).

o Last Line Mode (Ex Mode):

 Entering last line mode (:, /).

 Saving (:w, :wq, :x).

 Quitting (:q, :q!).

 Searching (/pattern, ?pattern, n, N).

 Set options (e.g., :set nu).

• 3.3 How to Write, Save, Execute a Shell Script in Vi Editor: (0.5 Hour)

o Creating a new file with vi.

o Adding the shebang line (#!/bin/bash).

o Writing simple shell commands.

o Saving the script (:wq).

o Making the script executable (chmod +x scriptname.sh).

o Executing the script (./scriptname.sh).

________________________________________

Teaching Methodology:

• Lectures and theoretical explanations for OS concepts.

• Demonstrations of Linux commands and Vi editor usage.

• Hands-on lab sessions for students to practice commands and editor operations.

• Small exercises and assignments for practical application.

Assessment:

• Quizzes on OS concepts.

• Practical lab exams for Linux commands and Vi editor.

Due to the extensive nature of the request, providing the full, detailed content with all relevant examples, diagrams, facts, and figures for a 12-hour unit in a single response is beyond the scope of what can be effectively generated here. This would essentially be a condensed textbook chapter.

However, I can provide a structured outline with significant detail for each section, including where diagrams and examples would be crucial, and relevant facts/figures where applicable. This will give you a robust framework from which you can easily expand with specific visuals and deeper practical exercises.

For actual diagrams, you would typically use drawing tools or readily available images (e.g., "Operating System Architecture Diagram," "Linux File System Hierarchy Diagram"). For facts and figures, these would often be historical dates, performance metrics, or market share data, which I will indicate where relevant.

________________________________________

UNIT-I: Operating Systems, Linux, and Vi Editor - Detailed Content Outline

________________________________________

Part 1: Introduction to Operating Systems (Approx. 5 Hours)

Objective: To understand the fundamental concepts of operating systems, their functions, and various types.

________________________________________

1.1 What is an Operating System? (1 Hour)

• Definition: An operating system (OS) is system software that manages computer hardware and software resources and provides common services for computer programs. It acts as an intermediary between the user and the computer hardware.

• Role of an OS:

o Resource Manager: Manages all hardware (CPU, memory, I/O devices) and software resources (programs, data).

o User Interface: Provides a way for users to interact with the computer (e.g., GUI, CLI).

o Program Execution Environment: Provides the necessary environment for applications to run.

o Abstractions: Hides the complexity of the hardware from application programmers.

• Analogy: Think of an OS as the "government" of your computer. It manages resources, enforces rules, and provides services to its "citizens" (applications and users).

• Why is it needed? Without an OS, every application would need to manage hardware directly, leading to complex, incompatible, and inefficient software.

• Components: Briefly mention kernel, shell, file system, utilities, applications.

o Diagram Idea: A layered diagram showing:

 User Applications at the top

 System Programs/Utilities

 Operating System (Kernel)

 Hardware at the bottom

 Arrows indicating interactions.

________________________________________

1.2 Functions of an Operating System: (1.5 Hours)

• 1.2.1 Process Management:

o Definition of a Process: A program in execution.

o Key Activities:

 Process Creation & Termination: How new programs are started and stopped.

 Process Scheduling: Allocating CPU time to different processes (e.g., Round Robin, FCFS - brief mention).

 Process Synchronization: Coordinating concurrent processes to prevent data inconsistencies (e.g., mutexes, semaphores - brief conceptual mention).

 Inter-process Communication (IPC): Mechanisms for processes to exchange information (e.g., pipes, message queues - brief conceptual mention).

o Example: Running multiple applications simultaneously (browser, music player, word processor). The OS manages their CPU access.

• 1.2.2 Memory Management:

o Purpose: Allocating and deallocating memory space to processes, ensuring protection, and managing virtual memory.

o Key Activities:

 Memory Allocation/Deallocation: Assigning RAM to programs when they start and reclaiming it when they finish.

 Memory Protection: Preventing one process from accessing another process's memory space.

 Virtual Memory (Brief): Concept of using disk space as an extension of RAM, allowing programs larger than physical memory to run.

o Diagram Idea: Simple diagram showing physical memory divided into partitions for different processes, or a conceptual view of virtual memory mapping.

• 1.2.3 File Management:

o Purpose: Organizing, storing, retrieving, and protecting files on secondary storage.

o Key Activities:

 File Creation & Deletion: Managing the lifecycle of files.

 Directory Management: Organizing files into logical structures (folders).

 File Access Methods: Sequential, direct.

 File Protection: Access control lists (read, write, execute permissions).

o Example: Saving a document, creating a new folder, deleting old photos.

• 1.2.4 Device Management:

o Purpose: Managing I/O devices (printers, keyboards, mice, network cards, disks).

o Key Activities:

 Device Drivers: Software modules that allow the OS to communicate with specific hardware devices.

 Buffering & Spooling: Improving I/O efficiency.

o Example: Printing a document. The OS handles communication with the printer driver.

• 1.2.5 Security and Protection:

o Purpose: Protecting system resources from unauthorized access and malicious programs.

o Mechanisms: User authentication, access control, firewalls (at OS level), encryption.

• 1.2.6 Error Handling:

o Purpose: Detecting and responding to errors (hardware failures, software errors, I/O errors).

o Mechanisms: Error logs, crash dumps, system recovery.

________________________________________

1.3 Types of Operating Systems: (2.5 Hours)

• 1.3.1 Simple Batch Systems:

o Concept: Jobs were submitted on punch cards or tape to an operator. The operator batched similar jobs together and fed them to the computer.

o Operation: CPU was idle during I/O operations. No direct user interaction during execution.

o Limitations: Very low CPU utilization, long turnaround time, no interactivity.

o Fact: Prevalent in the 1950s and early 1960s.

o Diagram Idea: Flowchart showing job submission, batching, execution, and output.

• 1.3.2 Multiprogrammed Batch Systems:

o Concept: The OS keeps multiple jobs in memory simultaneously. When one job performs I/O, the CPU switches to another ready job.

o Operation: Overlaps CPU execution with I/O operations.

o Benefits: Increased CPU utilization, improved throughput.

o Limitations: Still non-interactive, complex scheduling.

o Fact: Emerged in the mid-1960s.

o Diagram Idea: Memory divided into partitions, showing multiple jobs residing in memory, and CPU switching between them.

• 1.3.3 Time-Sharing Systems (Multitasking Systems):

o Concept: A logical extension of multiprogramming. The CPU switches between jobs so frequently that users can interact with each program while it is running. Each user gets a small slice of CPU time (time slice/quantum).

o Operation: Provides interactive computing. A user can run multiple programs concurrently.

o Benefits: Interactivity, responsiveness, allows multiple users to share a single computer.

o Example: Modern desktop OS (Windows, macOS, Linux) running multiple applications simultaneously.

o Fact: Pioneered by MIT's CTSS in the early 1960s.

o Diagram Idea: A timeline showing CPU time slices being allocated to different users/processes in a round-robin fashion.

• 1.3.4 Personal-Computer Systems:

o Concept: Designed for single users, emphasizing user-friendliness and graphical interfaces.

o Evolution: From command-line interfaces (DOS) to graphical user interfaces (Windows, macOS).

o Characteristics: Focus on individual productivity, direct user control, extensive peripheral support.

o Fact: The IBM PC (1981) and Apple Macintosh (1984) revolutionized personal computing.

• 1.3.5 Parallel Systems (Multiprocessor Systems):

o Concept: Systems with multiple CPUs or processing cores sharing a common memory and bus.

o Types:

 Symmetric Multiprocessing (SMP): Each processor runs an identical copy of the OS and all processors communicate with each other. Most common type.

 Asymmetric Multiprocessing (AMP): Each processor is assigned a specific task.

o Benefits: Increased throughput, increased reliability (graceful degradation), cost-effective for high-performance tasks.

o Example: Modern multi-core CPUs (Intel i7, AMD Ryzen).

o Diagram Idea: Multiple CPU cores connected to shared memory.

• 1.3.6 Distributed Systems:

o Concept: A collection of independent computers that appear to the users as a single coherent system. They communicate over a network.

o Characteristics: Networked, resource sharing, client-server models, peer-to-peer.

o Benefits: Resource sharing, computation speed-up, reliability (fault tolerance), communication.

o Challenges: Network latency, data consistency, security, complex programming.

o Example: Cloud computing (AWS, Azure), Google Docs (shared editing), network file systems (NFS).

o Diagram Idea: Multiple computers connected via a network, sharing resources.

• 1.3.7 Real-Time Systems:

o Concept: Systems where the correctness of computations depends not only on the logical result but also on the time at which the result is produced.

o Types:

 Hard Real-Time Systems: Strict deadlines; missing a deadline is a system failure (e.g., flight control, medical devices, industrial control).

 Soft Real-Time Systems: Deadlines are desirable but not critical; missing a deadline results in degraded performance but not system failure (e.g., multimedia streaming, online gaming).

o Characteristics: Deterministic, predictable, fast context switching, specialized kernels.

o Fact: Used extensively in embedded systems.

________________________________________

Part 2: Introduction to Linux (Approx. 5 Hours)

Objective: To gain a basic understanding of the Linux operating system architecture and essential command-line operations.

________________________________________

2.1 Architecture of Linux OS: (1 Hour)

• Linux Kernel:

o The core of the OS.

o Monolithic Kernel: Most Linux distributions use a monolithic kernel, meaning the entire OS (process management, memory management, file system, device drivers) runs in a single address space.

o Role: Directly interacts with hardware, manages resources, provides system calls to user-space programs.

• Shell:

o A command-line interpreter (e.g., Bash, Zsh).

o Provides an interface for users to interact with the kernel by executing commands.

• User Space:

o Where user applications, system utilities, and libraries run.

o Communicates with the kernel via system calls.

• Hardware: The physical components of the computer.

• File System: The structured way in which files are organized and stored.

• Diagram Idea: A clear diagram showing the layers: Hardware -> Kernel -> Shell/System Libraries -> User Applications, with arrows indicating communication flow.

________________________________________

2.2 Basic Directory Structure of Linux: (1 Hour)

• Linux File System Hierarchy Standard (FHS): A standard that defines the directory structure and the contents of various directories.

• Root Directory (/): The top-level directory from which all other directories branch.

• Key Directories and their Purpose (with examples):

o /bin: (Binaries) Essential user command binaries (e.g., ls, cp, mv).

o /sbin: (System Binaries) Essential system administration binaries (e.g., fdisk, shutdown).

o /etc: (Et Cetera) Host-specific system-wide configuration files (e.g., passwd, fstab).

o /home: User home directories (e.g., /home/username).

o /usr: (Unix System Resources) Read-only user data; contains most user utilities and applications (e.g., /usr/bin, /usr/local).

o /var: (Variable) Variable data files, often growing in size (e.g., logs in /var/log, mail in /var/mail).

o /tmp: (Temporary) Temporary files, cleared on reboot.

o /dev: (Devices) Device files (e.g., /dev/sda1 for hard drives, /dev/tty for terminals).

o /proc: (Processes) Virtual filesystem providing process and kernel information (runtime info, not stored on disk).

o /mnt: (Mount) Temporary mount point for removable file systems (e.g., USB drives).

o /media: Mount point for removable media like CD-ROMs, USB drives.

o /opt: (Optional) Optional software packages not part of the standard system.

o /lib: (Libraries) Essential shared libraries for binaries in /bin and /sbin.

o /boot: Files required to boot the system (e.g., GRUB bootloader, kernel images).

• Diagram Idea: A tree-like diagram showing the root (/) and its primary subdirectories, with brief descriptions.

________________________________________

2.3 Basic Commands of Linux: (3 Hours)

Teaching Approach: For each command, explain its purpose, basic syntax, provide a simple example, and highlight useful options. Encourage hands-on practice.

• 2.3.1 Help Commands:

o man <command>: Manual pages. Comprehensive documentation.

 Example: man ls (press q to quit).

 Fact: Man pages are typically categorized into 8 sections (e.g., 1 for commands, 2 for system calls).

o info <command>: GNU info documentation. More structured and hyperlinked than man pages.

 Example: info ls (navigate with arrow keys, q to quit).

o <command> --help / help <builtin_command>: Brief usage summary. For most external commands, command --help works. For shell built-ins (like cd), use help.

 Example: ls --help, help cd.

o whatis <command>: One-line description from man pages.

 Example: whatis ls.

o apropos <keyword>: Search man pages by keyword. Useful when you don't know the exact command name.

 Example: apropos directory.

• 2.3.2 Basic Directory Navigation & File Management:

o pwd: Print Working Directory. Shows your current location.

 Example: pwd (Output: /home/user).

o ls: List directory contents.

 Syntax: ls [options] [file...]

 Examples:

 ls: List files in current directory.

 ls -l: Long listing format (permissions, owner, size, date).

 ls -a: List all files, including hidden files (start with .).

 ls -lh: Long listing, human-readable sizes.

 ls -F: Append indicator (*/@/=|) to entries.

o cd: Change Directory.

 Examples:

 cd /home/user/documents: Go to specific path.

 cd ..: Go up one level.

 cd ~: Go to home directory.

 cd -: Go to the previous directory.

 cd: Go to home directory (same as cd ~).

o mkdir <directory_name>: Make Directory.

 Example: mkdir my_new_folder

 Option: mkdir -p a/b/c (creates parent directories if they don't exist).

o rmdir <directory_name>: Remove Empty Directory.

 Example: rmdir empty_folder

o cat <filename>: Concatenate and display file content.

 Example: cat my_document.txt

 Usage: Often used to view small text files.

o mv <source> <destination>: Move or rename files/directories.

 Examples:

 mv file.txt new_file.txt: Rename file.

 mv file.txt /home/user/documents/: Move file to another directory.

 mv folder1 folder2: Rename folder1 to folder2.

o cp <source> <destination>: Copy files/directories.

 Examples:

 cp file.txt copy_of_file.txt: Copy a file.

 cp -r folder1 /home/user/backup/: Recursively copy a directory and its contents.

 Option: -i (interactive, prompt before overwrite).

o rm <file_or_directory>: Remove files/directories. (Use with caution!)

 Examples:

 rm old_file.txt: Remove a file.

 rm -r old_folder: Recursively remove a directory and its contents.

 rm -f unwanted_file.txt: Force removal (no prompt).

 rm -rf /path/to/critical_data: DANGER! This command can permanently delete data without warning. Emphasize extreme caution.

o file <filename>: Determine file type.

 Example: file my_script.sh, file my_image.jpg.

• 2.3.3 System Information & Utility Commands:

o date: Display or set the system date and time.

 Example: date (Output: Mon Jun 16 15:16:42 IST 2025).

o cal: Display a calendar.

 Example: cal, cal 2025, cal 6 2025.

o echo <text>: Display a line of text.

 Example: echo "Hello, World!"

 Usage: Useful for displaying messages in scripts, showing variable values (echo $PATH).

o bc: Arbitrary precision calculator language.

 Example: Type bc then 10/3, sqrt(2). Type quit to exit.

o who: Show who is logged on.

 Example: who (Output: username tty1 2025-06-16 15:10).

o whoami: Print effective userid.

 Example: whoami (Output: username).

o hostname: Print or set system hostname.

 Example: hostname (Output: mycomputer).

o uname: Print system information.

 Example: uname -a (All information: kernel name, nodename, kernel release, kernel version, machine hardware name, operating system).

o tty: Print the file name of the terminal connected to standard input.

 Example: tty (Output: /dev/pts/0).

o alias: Create or display aliases. Shortcuts for longer commands.

 Examples:

 alias ll='ls -lh' (creates an alias ll for ls -lh).

 alias (shows all defined aliases).

 unalias ll (removes the alias).

 Fact: Aliases are typically stored in shell configuration files (.bashrc, .zshrc) for persistence.

________________________________________

Part 3: Vi Editor (Approx. 2 Hours)

Objective: To learn the basics of the Vi text editor, including its modes and how to perform basic file operations and script execution.

________________________________________

3.1 Vi Basics: (0.5 Hour)

• What is Vi/Vim?

o Vi (Visual Editor): A powerful, screen-oriented text editor. One of the oldest and most widely used text editors on Unix-like systems.

o Vim (Vi Improved): A highly popular and enhanced version of Vi, providing more features and extensibility. (Often, when people say "Vi," they mean Vim).

• Why Learn Vi?

o Ubiquitous: Available on virtually every Unix/Linux system, even minimal installations. Essential for server administration.

o Efficient: Designed for keyboard-only operation, enabling very fast editing once mastered.

o Powerful: Supports complex text manipulation, macros, scripting.

• Starting Vi:

o vi <filename>: Opens filename for editing. If filename doesn't exist, it creates a new empty file.

o vi: Opens an empty buffer (you'll need to save with a filename later).

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3.2 Three Modes of Vi Editor: (1 Hour)

• Key Concept: Vi is modal, meaning its behavior changes based on the current mode. Understanding modes is fundamental.

• 3.2.1 Command Mode (Normal Mode):

o Default mode when you open Vi.

o Purpose: For navigation, deletion, copying, pasting, and issuing commands.

o Cannot type text directly in this mode.

o Entering from other modes: Press Esc.

o Common Commands:

 Navigation:

 h, j, k, l: Move cursor (left, down, up, right).

 w: Move to the start of the next word.

 b: Move to the start of the previous word.

 0 (zero): Move to the beginning of the line.

 $: Move to the end of the line.

 G: Go to the last line of the file.

 gg: Go to the first line of the file.

 :[line_number]: Go to a specific line number (e.g., :5 to go to line 5).

 Deletion:

 x: Delete character under cursor.

 dd: Delete the current line.

 dw: Delete from cursor to end of word.

 d$: Delete from cursor to end of line.

 d^ (or d0): Delete from cursor to beginning of line.

 D: Delete from cursor to end of line (same as d$).

 Copying (Yank) & Pasting (Put):

 yy: Yank (copy) the current line.

 yw: Yank word.

 p: Put (paste) after the cursor/line.

 P: Put (paste) before the cursor/line.

 Undo/Redo:

 u: Undo last change.

 Ctrl+r: Redo (Vim specific, Vi might not have it).

• 3.2.2 Insert Mode:

o Purpose: To insert or type text into the file.

o Entering from Command Mode:

 i: Insert before the cursor.

 I: Insert at the beginning of the current line.

 a: Append (insert) after the cursor.

 A: Append (insert) at the end of the current line.

 o: Open (insert) a new line below the current line.

 O: Open (insert) a new line above the current line.

o Exiting to Command Mode: Press Esc.

o Example: After typing i, you can type anything. Press Esc to stop inserting.

• 3.2.3 Last Line Mode (Ex Mode / Command-Line Mode):

o Purpose: For file operations (save, quit), search and replace, setting editor options.

o Entering from Command Mode: Press : (colon) or / (forward slash for search).

o Common Commands (prefixed with :):

 Saving & Quitting:

 :w: Write (save) the file.

 :q: Quit (if no changes, or changes saved).

 :wq: Write and quit.

 :x: Write and quit (only if changes were made).

 :q!: Quit without saving (discard changes).

 :w!: Force write (e.g., if file is read-only).

 Search:

 /pattern: Search forward for pattern.

 ?pattern: Search backward for pattern.

 n: Go to the next match.

 N: Go to the previous match.

 Set Options:

 :set nu: Display line numbers.

 :set nonu: Hide line numbers.

 :set autoindent: Enable auto-indentation.

 :set paste: Paste mode (useful when pasting code).

 Running Shell Commands (briefly):

 :!ls: Run an external shell command (ls) and return to Vi.

• Diagram Idea: A state transition diagram showing the three modes and the key commands to move between them (e.g., Esc from Insert to Command, i/a/o from Command to Insert, : from Command to Last Line).

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3.3 How to Write, Save, Execute a Shell Script in Vi Editor: (0.5 Hour)

• Step-by-Step Example:

1. Open Vi to create a new script:

Bash

vi my_first_script.sh

2. Enter Insert Mode: Press i.

3. Write the script content:

 Add the shebang line (essential for execution): #!/bin/bash

 Add comments: # This is my first shell script

 Add commands:

Bash

#!/bin/bash

# This is my first shell script

echo "Hello from my script!"

ls -l

pwd

4. Exit Insert Mode: Press Esc.

5. Save and Quit: Type :wq and press Enter. (Alternatively, :x).

6. Make the script executable:

 After quitting Vi, use the chmod command in your terminal:

Bash

chmod +x my_first_script.sh

 Explanation: chmod changes file permissions. +x adds execute permission.

7. Execute the script:

 From your terminal, in the same directory as the script:

Bash

./my_first_script.sh

 Explanation: ./ tells the shell to look for the executable in the current directory.

• Expected Output:

• Hello from my script!

• total X

• -rwxrwxr-x 1 user user Y Jun 16 15:30 my_first_script.sh

• ... (other files in the directory) ...

• /home/user

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General Considerations for the 12-Hour Unit:

• Hands-on Practice: Emphasize that the Linux commands and Vi editor sections require significant hands-on time. Theory alone is insufficient.

• Live Demonstrations: Crucial for all command-line and editor topics.

• Troubleshooting: Be prepared to help students with common errors (e.g., "command not found," "permission denied," getting stuck in Vi).

• Repetition and Reinforcement: Linux commands should be practiced regularly.

• Further Reading: Encourage students to consult the suggested textbooks for deeper dives into each topic.

• Interactive Learning: Use questions and small tasks during the lectures to keep students engaged.

This detailed outline should serve as an excellent foundation for building out your 12-hour UNIT-I curriculum. Remember to integrate actual diagrams and conduct practical sessions to maximize learning.

Sources

Generate Audio Overview

Okay, here's a detailed content outline for UNIT-II, focusing on Processes, CPU Scheduling, Process Synchronization, and relevant Linux commands, designed for a 12-hour duration. I'll integrate examples, facts, and figures where appropriate.

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UNIT-II: Processes, CPU Scheduling, and Process Synchronization

No. of Hours: 12

Chapter/Book Reference: TB1 [Chapters 3, 5, 6]; TB2 [Chapter 9]

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Part 1: Processes (Approx. 3 Hours)

Objective: To understand the concept of a process, its lifecycle, and how the operating system manages processes.

• 2.1 Process Concept (1.5 Hours)

o Definition: A process is a program in execution. It is an active entity, whereas a program is a passive entity (like a file stored on disk).

 Fact: The concept of a "process" was formalized in the early 1960s, a fundamental shift from simple batch jobs.

o Process vs. Program:

 Program: Static, set of instructions, stored on disk.

 Process: Dynamic, instance of a program being executed, active entity in memory.

 Analogy: A program is like a recipe; a process is like a chef actively cooking that recipe. Many chefs can cook the same recipe simultaneously.

o Process State: A process goes through various states during its lifetime.

 Diagram Idea: A clear state transition diagram:

 New: The process is being created.

 Running: Instructions are being executed on the CPU.

 Waiting (Blocked): The process is waiting for some event to occur (e.g., I/O completion, a signal).

 Ready: The process is waiting to be assigned to a processor (ready to run, just needs CPU).

 Terminated: The process has finished execution.

 Explanation: Elaborate on the transitions (e.g., dispatch from Ready to Running, interrupt from Running to Ready, I/O wait from Running to Waiting, I/O completion from Waiting to Ready).

o Process Control Block (PCB): A data structure maintained by the OS for each process. It contains all the information needed to manage the process.

 Contents of a PCB (Examples):

 Process State: (New, Ready, Running, etc.)

 Program Counter: Address of the next instruction to be executed.

 CPU Registers: Values of general-purpose registers, stack pointers, etc.

 CPU Scheduling Information: Process priority, pointers to scheduling queues.

 Memory-Management Information: Base/limit registers, page tables, segment tables.

 Accounting Information: CPU usage, real time used, time limits, process ID (PID).

 I/O Status Information: List of open files, list of I/O devices allocated.

 Diagram Idea: A block diagram representing a PCB with fields.

 Fact: PCBs are crucial for context switching, allowing the OS to save and restore the state of processes.

• 2.2 Process Scheduling (1 Hour)

o Purpose: To maximize CPU utilization and provide fair access to the CPU for all processes.

o Scheduling Queues:

 Job Queue: All processes in the system.

 Ready Queue: Processes residing in main memory, ready and waiting to execute.

 Device Queues: Processes waiting for a particular I/O device.

 Diagram Idea: Flowchart showing processes moving between job queue, ready queue, and device queues.

o Schedulers:

 Long-Term Scheduler (Job Scheduler): Selects processes from the job queue and loads them into memory for execution (controls degree of multiprogramming). Less frequent.

 Short-Term Scheduler (CPU Scheduler): Selects processes from the ready queue and allocates the CPU to one of them. Very frequent (milliseconds).

 Medium-Term Scheduler (Optional): Swaps processes in and out of memory to reduce the degree of multiprogramming or improve the mix of processes. Used in time-sharing systems.

o Context Switch:

 Definition: The process of saving the state of the current running process and loading the state of the next process to run.

 Steps:

1. Save the CPU state (registers, program counter) of the current process into its PCB.

2. Load the CPU state from the PCB of the new process.

 Overhead: Context switch is pure overhead; no useful work is done during this time.

 Fact: Context switch times vary by CPU and OS, but typically range from a few microseconds to hundreds of microseconds. A typical context switch on modern systems might take 1-10 microseconds.

• 2.3 Operations on Processes (0.5 Hour)

o Process Creation:

 Parent-Child Relationship: A process can create new processes (children).

 Resource Sharing: Parent and child can share all, subset, or none of resources.

 Execution: Parent can continue concurrently with child, or wait for child to terminate.

 Address Space: Child can be a duplicate of parent, or have a new program loaded into it.

 UNIX Example: fork() system call creates a child process (duplicate of parent); exec() system call replaces the child's program with a new one.

o Process Termination:

 Normal Exit: Process finishes its last instruction and asks the OS to terminate it.

 Abnormal Termination:

 By Parent: Parent process terminates child (e.g., child exceeds resource usage, task no longer needed).

 By OS: If an error occurs (e.g., division by zero, invalid memory access), or if the OS needs to terminate processes for resource management.

 exit() system call: Used by a process to terminate itself.

 wait() system call: Used by a parent to wait for a child to terminate.

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Part 2: CPU Scheduling (Approx. 4 Hours)

Objective: To understand the fundamental concepts of CPU scheduling, various scheduling criteria, and common scheduling algorithms.

• 2.4 Basic Concepts (1 Hour)

o CPU-I/O Burst Cycle: Processes alternate between CPU bursts (computations) and I/O bursts (waiting for I/O). CPU-bound jobs have long CPU bursts, I/O-bound jobs have many short CPU bursts.

 Diagram Idea: A graph showing alternating CPU and I/O bursts.

o CPU Scheduler (Short-Term Scheduler): Selects from processes in memory that are ready to execute, and allocates the CPU to one of them.

o Dispatcher: The module that gives control of the CPU to the process selected by the short-term scheduler. It performs:

 Context switching.

 Switching to user mode.

 Jumping to the proper location in the user program to restart that program.

o Dispatch Latency: The time taken by the dispatcher to stop one process and start another running.

o Preemptive vs. Non-Preemptive Scheduling:

 Non-Preemptive: Once the CPU is allocated to a process, it holds the CPU until it voluntarily releases it (e.g., by terminating or switching to the waiting state).

 Preemptive: The CPU can be taken away from a process even if it is still running, typically after a fixed time quantum or if a higher-priority process becomes ready.

 Fact: Most modern operating systems use preemptive scheduling for better responsiveness, especially in time-sharing systems.

• 2.5 Scheduling Criteria (0.5 Hour)

o CPU Utilization: Keep the CPU as busy as possible (range 0-100%).

 Fact: For a real system, CPU utilization typically ranges from 40% (lightly loaded) to 90% (heavily loaded).

o Throughput: The number of processes completed per unit time.

o Turnaround Time: The total time from submission to completion (sum of waiting, ready, execution, and I/O times).

o Waiting Time: The total time a process spends in the ready queue.

o Response Time: The time from submission of a request until the first response is produced (for interactive systems).

o Fairness: Each process should get a fair share of the CPU.

• 2.6 Scheduling Algorithms (2.5 Hours)

o Assumptions for Examples: Typically, we'll assume processes arrive at time 0 unless specified, and non-preemptive execution for simplicity first, then introduce preemption. Gantt charts are essential here.

o 2.6.1 First-Come, First-Served (FCFS) Scheduling:

 Principle: Processes are executed in the order they arrive in the ready queue.

 Type: Non-preemptive.

 Example: | Process | Burst Time | | :------ | :--------- | | P1 | 24 | | P2 | 3 | | P3 | 3 | Gantt Chart: P1 (0-24) -> P2 (24-27) -> P3 (27-30) Calculations: * P1: Wait=0, Turnaround=24 * P2: Wait=24, Turnaround=27 * P3: Wait=27, Turnaround=30 * Avg Waiting Time: (0+24+27)/3 = 17 * Avg Turnaround Time: (24+27+30)/3 = 27

 Convoy Effect: Short processes stuck behind long processes, leading to increased average waiting time.

 Benefits: Simple to implement.

 Drawbacks: High average waiting time, poor for time-sharing systems.

o 2.6.2 Shortest-Job-First (SJF) Scheduling:

 Principle: The CPU is allocated to the process with the smallest next CPU burst.

 Types:

 Non-Preemptive SJF: Once a process starts, it runs to completion.

 Preemptive SJF (Shortest-Remaining-Time-First, SRTF): If a new process arrives with a shorter remaining burst time than the currently executing process, the current process is preempted.

 Example (Non-Preemptive): | Process | Arrival Time | Burst Time | | :------ | :----------- | :--------- | | P1 | 0 | 7 | | P2 | 2 | 4 | | P3 | 4 | 1 | | P4 | 5 | 4 | Gantt Chart: P1 (0-7) -> P3 (7-8) -> P2 (8-12) -> P4 (12-16) (assuming P1 starts as only option, then P3 is shortest after P1 finishes) Calculations and comparison to FCFS to show improvement.

 Example (Preemptive - SRTF): | Process | Arrival Time | Burst Time | | :------ | :----------- | :--------- | | P1 | 0 | 8 | | P2 | 1 | 4 | | P3 | 2 | 9 | | P4 | 3 | 5 | Gantt Chart: P1(0-1) -> P2(1-5) -> P4(5-10) -> P1(10-17) -> P3(17-26) Calculations: (Detailed step-by-step calculation of waiting/turnaround times).

 Benefits: Optimal - gives the minimum average waiting time for a given set of processes.

 Drawbacks: Cannot be implemented in practice as CPU burst times are not known in advance (predictive mechanisms are used). Starvation for long jobs.

o 2.6.3 Priority Scheduling:

 Principle: Each process is assigned a priority, and the CPU is allocated to the process with the highest priority.

 Type: Can be preemptive or non-preemptive.

 Problem: Starvation/Indefinite blocking (low-priority processes may never execute).

 Solution: Aging - gradually increasing the priority of processes that wait for a long time.

 Example: | Process | Burst Time | Priority (1=Highest) | | :------ | :--------- | :------------------- | | P1 | 10 | 3 | | P2 | 1 | 1 | | P3 | 2 | 4 | | P4 | 1 | 5 | | P5 | 5 | 2 | Gantt Chart (Non-Preemptive, all arrive at 0): P2 (0-1) -> P5 (1-6) -> P1 (6-16) -> P3 (16-18) -> P4 (18-19) Calculations.

o 2.6.4 Round-Robin (RR) Scheduling:

 Principle: Designed for time-sharing systems. Each process gets a small unit of CPU time, called a time quantum (or time slice). If the process doesn't complete within the quantum, it's preempted and added to the end of the ready queue.

 Type: Preemptive.

 Time Quantum:

 Too large: Behaves like FCFS.

 Too small: High context-switching overhead.

 Fact: Typical time quanta range from 10 to 100 milliseconds. Context switch time is usually less than 1% of the time quantum.

 Example: | Process | Burst Time | | :------ | :--------- | | P1 | 24 | | P2 | 3 | | P3 | 3 | Time Quantum = 4 ms Gantt Chart: P1(0-4) -> P2(4-7) -> P3(7-10) -> P1(10-14) -> P1(14-18) -> P1(18-22) -> P1(22-24) Calculations (Waiting and Turnaround times).

 Benefits: Good response time, fair for interactive systems.

 Drawbacks: Higher average turnaround time than SJF, higher context switching overhead.

o 2.6.5 Multilevel Queue Scheduling (Brief Mention):

 Concept: Divides the ready queue into multiple separate queues (e.g., foreground interactive, background batch). Each queue has its own scheduling algorithm.

 Example: Interactive processes might use RR, batch processes might use FCFS.

 Inter-queue scheduling: Fixed-priority preemptive scheduling between queues, or time slicing between queues.

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Part 3: Process Synchronization (Approx. 3 Hours)

Objective: To understand the critical-section problem and how semaphores can be used to solve it.

• 2.7 Background (1 Hour)

o Concurrent Access to Shared Data: When multiple processes or threads access and manipulate the same shared data concurrently, the outcome of the execution depends on the order of access. This can lead to incorrect results.

o Race Condition: A situation where several processes access and manipulate shared data concurrently and the final outcome depends on the particular order in which the access takes place.

 Example: counter++ and counter-- operations on a shared variable counter.

 counter++ is usually: register1 = counter; register1 = register1 + 1; counter = register1;

 counter-- is usually: register2 = counter; register2 = register2 - 1; counter = register2;

 Scenario (Initial counter=5):

1. P1 executes register1 = counter (register1=5).

2. P2 executes register2 = counter (register2=5).

3. P1 executes register1 = register1 + 1 (register1=6).

4. P2 executes register2 = register2 - 1 (register2=4).

5. P1 executes counter = register1 (counter=6).

6. P2 executes counter = register2 (counter=4). Final counter is 4 instead of 5.

 Diagram Idea: Flowchart showing interleaving of instructions leading to an incorrect result.

o Critical Section: A segment of code where the shared resources are accessed.

o Critical-Section Problem: Designing a protocol to ensure that when one process is executing in its critical section, no other process can be executing in its critical section.

• 2.8 The Critical-Section Problem (1 Hour)

o Requirements for a Solution:

 Mutual Exclusion: If process Pi is executing in its critical section, then no other processes can be executing in their critical sections.

 Progress: If no process is executing in its critical section and some processes want to enter their critical sections, then only those processes that are not executing in their remainder section can participate in deciding which will enter its critical section next, and this selection cannot be postponed indefinitely.

 Bounded Waiting: There exists a limit on the number of times that other processes are allowed to enter their critical sections after a process has made a request to enter its critical section and before that request is granted.

o Peterson's Solution (For two processes):

 Variables: int turn;, boolean flag[2];

 Code for Pi:

do {

flag[i] = TRUE;

turn = j;

while (flag[j] && turn == j); // Busy waiting

// Critical Section

flag[i] = FALSE;

// Remainder Section

} while (TRUE);

 Explanation: How it satisfies Mutual Exclusion, Progress, and Bounded Waiting.

 Drawbacks: Busy waiting (processor time wasted), limited to two processes, complex for many processes.

• 2.9 Semaphores (1 Hour)

o Definition: A synchronization tool that provides a more sophisticated way for processes to synchronize their activities. A semaphore S is an integer variable that, apart from initialization, is accessed only through two standard atomic operations: wait() and signal().

 wait(S) (or P):

 wait(S) {

 while (S <= 0); // busy wait

 S--;

 }

 signal(S) (or V):

 signal(S) {

 S++;

 }

 Atomicity: The wait() and signal() operations must be indivisible.

o Types of Semaphores:

 Counting Semaphores: Integer value can range over an unrestricted domain. Used to control access to a resource with multiple instances.

 Binary Semaphores (Mutex Locks): Integer value can range only between 0 and 1. Used to enforce mutual exclusion (like a lock). Functionally equivalent to mutex locks.

o Semaphore Solution to Critical Section Problem:

 Shared Variable: semaphore mutex; (initialized to 1)

 Code for Process Pi:

do {

wait(mutex);

// Critical Section

signal(mutex);

// Remainder Section

} while (TRUE);

 Explanation: How wait(mutex) ensures only one process enters, and signal(mutex) releases the lock.

o Drawbacks of Semaphores:

 Busy Waiting (Spinlock): If the critical section is small, busy waiting can be more efficient. For larger critical sections, it's wasteful.

 Priority Inversion (briefly): A lower-priority process holds a lock needed by a higher-priority process.

 Deadlock and Starvation: Incorrect use of semaphores can lead to these problems.

o Implementing Semaphores (without busy waiting):

 Instead of busy waiting, processes can block themselves (go to waiting state) if the semaphore value is not positive.

 The semaphore structure typically includes an integer value and a list of processes waiting for that semaphore.

 block() and wakeup() operations.

 Fact: This "blocking semaphore" implementation is what is generally used in modern OS kernels.

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Part 4: Process Related Commands in Linux (Approx. 2 Hours)

Objective: To introduce practical Linux commands for viewing and managing processes, and a conceptual overview of related system calls.

• 2.10 Process Related Commands in Linux (1.5 Hours)

o ps: Process Status. Displays information about current processes.

 Common Options:

 ps: Processes owned by the current user.

 ps -e: All processes on the system.

 ps -f: Full format listing (UID, PID, PPID, C, STIME, TTY, TIME, CMD).

 ps aux: BSD-style, showing all users' processes. (Often combined with grep for specific processes, e.g., ps aux | grep firefox).

 Output Columns Explained: PID, PPID, UID, CMD, TTY, STAT, START, TIME, %CPU, %MEM.

 Example: ps -ef | head -n 10

o top: Display Linux processes. Provides a dynamic, real-time view of running processes.

 Interactive Features: Sorting by CPU/memory, killing processes (k), renice (r), quitting (q).

 Output Explained: Load average, tasks summary, CPU states, memory usage, process list (PID, USER, PR, NI, VIRT, RES, SHR, S, %CPU, %MEM, TIME+, COMMAND).

 Example: Just top

o pstree: Display a tree structure of processes. Shows parent-child relationships.

 Example: pstree, pstree -p (show PIDs).

 Fact: The initial process (ancestor of all processes) typically has PID 1 (systemd or init).

o nice: Run a command with modified scheduling priority. nice allows you to set the niceness value (which influences priority).

 Niceness Values: Range from -20 (highest priority, least nice) to 19 (lowest priority, most nice). Default is 0.

 Syntax: nice -n <niceness_value> <command>

 Example:

 nice -n 10 sleep 60 &: Run sleep with lower priority.

 nice -n -5 my_cpu_bound_app: Run my_cpu_bound_app with slightly higher priority (requires root for negative nice values).

o renice: Alter the priority of running processes.

 Syntax: renice <niceness_value> -p <pid>

 Example:

 renice 5 -p 12345: Change process 12345's niceness to 5.

 sudo renice -10 -p 54321: Increase priority of process 54321 (requires sudo).

 Fact: nice and renice modify the "nice value" which affects the dynamic priority of a process in Linux's scheduling algorithm (e.g., Completely Fair Scheduler - CFS).

• 2.11 Process Related System Calls (Conceptual Overview) (0.5 Hour)

o System Calls: The programmatic interface to the services provided by the operating system.

o fork():

 Purpose: Creates a new process by duplicating the calling process. The child process is an exact copy of the parent.

 Return Values: Returns 0 to the child process, the PID of the child to the parent process, and -1 on error.

 Fact: On Linux, fork() is implemented using "copy-on-write" pages for efficiency.

o exec() (family of calls like execlp, execvp):

 Purpose: Replaces the current process's image (code, data, stack) with a new program. It does not create a new process; it transforms the current one.

 Example: A shell calls fork() to create a child, then the child calls exec() to load and run the command typed by the user.

o wait() / waitpid():

 Purpose: A parent process uses these to wait for a child process to terminate. This prevents "zombie processes" (terminated processes whose parent hasn't yet collected their exit status).

o exit():

 Purpose: Terminates the calling process normally. Returns an exit status to the parent process.

o kill():

 Purpose: Sends a signal to a process or process group. Can be used to terminate processes (e.g., kill -9 <PID> for a forceful termination).

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Teaching Methodology and Additional Notes:

• Diagrams are critical: For process states, scheduling queues, PCB, CPU-I/O burst cycle, and the critical section problem (race condition illustration, Peterson's solution, semaphore usage).

• Gantt Charts: Absolutely essential for explaining CPU scheduling algorithms. Spend time on drawing and calculating for each.

• Examples: Provide multiple numerical examples for scheduling algorithms. Work them out step-by-step.

• Interactive Demos: For Linux commands, a live terminal demonstration is invaluable. Have students follow along.

• Conceptual vs. Practical: Differentiate between the theoretical concept of a process/synchronization mechanism and its practical implementation or command-line interaction in Linux.

• Case Studies/Real-world Relevance: Briefly discuss how these concepts apply in real operating systems (e.g., how the Linux kernel implements scheduling, what kind of synchronization mechanisms browsers use).

• Problem Solving: Assign small problems for students to calculate waiting times, draw Gantt charts, or debug simple synchronization scenarios.

• Complexity: Acknowledge that process synchronization is a complex topic and that semaphores are a foundational but not the only solution (briefly mention mutexes, monitors if time allows, but stick to syllabus focus on semaphores).

This detailed outline covers the core requirements for UNIT-II, providing enough depth for a 12-hour module in a BCA program. Remember to supplement with engaging visuals and plenty of hands-on practice for the Linux commands.

It appears you've requested content for both UNIT-III and UNIT-IV. Due to the extensive nature of both units, I will provide a detailed outline with examples, facts, and figures for UNIT-III (Memory Management, Virtual Memory, Deadlocks) first.

Once you confirm, I can then proceed with UNIT-IV. This allows for a more manageable and detailed response for each complex topic.

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UNIT-III: Memory Management, Virtual Memory, and Deadlocks

No. of Hours: 12

Chapter/Book Reference: TB1 [Chapters 7, 8, 9]

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Part 1: Memory Management (Approx. 4 Hours)

Objective: To understand how the operating system manages main memory, allocates it to processes, and the different memory organization schemes.

• 3.1 Background (1 Hour)

o Main Memory (RAM): A large array of words or bytes, each with its own address. Volatile storage.

 Fact: RAM access times are typically in nanoseconds (e.g., 10-100 ns). Hard disk access times are in milliseconds (e.g., 5-10 ms) – a difference of 100,000 to 1,000,000 times! This speed difference makes memory management critical.

o CPU and Memory Interaction: CPU fetches instructions and data from memory. Memory Management Unit (MMU) is a hardware device that maps virtual to physical addresses.

o Binding of Instructions and Data to Memory:

 Compile Time: If memory location known a priori, absolute code can be generated. (e.g., MS-DOS .COM programs). Not flexible.

 Load Time: If memory location is not known at compile time, relocatable code is generated. Binding done at load time.

 Execution Time: Most common. Binding delayed until run time. Required if process can be moved during execution (swapping). Requires hardware support (MMU).

o Logical versus Physical Address Space:

 Logical Address (Virtual Address): Address generated by the CPU.

 Physical Address: Address seen by the memory unit (actual address on RAM).

 Memory-Management Unit (MMU): Hardware device that maps logical to physical addresses at run time.

 Diagram Idea: A diagram showing CPU generating a logical address, passing it to MMU, and MMU translating it to a physical address which then accesses RAM.

• 3.2 Swapping (0.5 Hour)

o Concept: A process can be temporarily swapped out of main memory to a backing store (e.g., fast disk) and then swapped back into main memory for continued execution.

o Purpose: Allows total physical memory of all processes to exceed actual physical memory. Used to implement multiprogramming with variable memory allocation.

o Backing Store: A fast disk large enough to accommodate copies of all memory images for all users, and provides direct access to these memory images.

o Roll Out, Roll In: Swapping variant used for priority-based scheduling; lower-priority process is swapped out to allow a higher-priority process to be loaded.

o Diagram Idea: Processes moving between RAM and backing store.

• 3.3 Contiguous Allocation (1 Hour)

o Concept: Each process is contained in a single, contiguous block of memory.

o Memory Protection: Achieved using a base register (holds the smallest physical address) and a limit register (holds the range of logical addresses). Every logical address must be within the limit, and is translated by adding the base address.

 Diagram Idea: A segment of memory with base and limit registers.

o Memory Allocation Strategies:

 First-Fit: Allocate the first hole that is big enough. (Fast).

 Best-Fit: Allocate the smallest hole that is big enough. (Produces smallest leftover hole, but searches entire list).

 Worst-Fit: Allocate the largest hole. (Produces largest leftover hole, which might be useful, but searches entire list).

 Example: Suppose holes are 10KB, 20KB, 4KB, 18KB. Process needs 12KB.

 First-Fit: Allocates 20KB hole.

 Best-Fit: Allocates 18KB hole.

 Worst-Fit: Allocates 20KB hole.

o Fragmentation:

 External Fragmentation: Total memory space exists to satisfy a request, but it is not contiguous.

 Internal Fragmentation: Allocated memory may be slightly larger than requested memory; this difference is wasted (e.g., fixed-size blocks).

 Compaction: Shuffle memory contents to place all free memory together in one large block. Costly.

• 3.4 Segmentation (0.75 Hour)

o Concept: A memory-management scheme that supports a user view of memory. A program is a collection of segments (e.g., code, data, stack, subroutines). Each segment has a name and a length.

o Logical Address: Composed of a (segment-number, offset).

o Segmentation Hardware: Uses a segment table to map 2D logical addresses to 1D physical addresses. Each entry in the segment table has a base (starting physical address) and limit (length of segment).

 Diagram Idea: CPU generating (segment, offset), MMU using segment table to get physical address.

o Advantages:

 Supports user view of memory.

 Allows programs to be broken into logical units.

 Simplifies handling of growing data structures.

 Supports shared code segments.

o Disadvantages: External fragmentation (though less severe than pure contiguous allocation).

• 3.5 Paging (0.75 Hour)

o Concept: Divides physical memory into fixed-size blocks called frames, and logical memory into blocks of the same size called pages.

o Purpose: Solves the problem of external fragmentation by allowing a process's physical address space to be non-contiguous.

o Logical Address: Composed of a (page-number, offset).

o Paging Hardware: Uses a page table to map logical page numbers to physical frame numbers. The offset remains the same.

 Diagram Idea: CPU generating (page #, offset), MMU using page table to get (frame #, offset) for physical address.

o Advantages:

 No external fragmentation.

 Efficient memory utilization.

 Simplifies memory allocation.

o Disadvantages:

 Internal fragmentation (last page of a process might not be fully utilized).

 Overhead of page table (can be large for 64-bit systems; solutions include multilevel paging, TLBs).

 Translation Lookaside Buffer (TLB): A small, fast hardware cache for page table entries.

 Fact: TLB hit rates typically range from 90% to 99%. A 99% hit rate with a 20ns TLB access time and 100ns memory access time means effective access time is 0.99 * 20 + 0.01 * (20 + 100) = 19.8 + 1.2 = 21ns. Without TLB, it would be 20 + 100 = 120ns.

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Part 2: Virtual Memory (Approx. 4 Hours)

Objective: To understand the concept of virtual memory, its implementation through demand paging, and page replacement algorithms.

• 3.6 Demand Paging (1 Hour)

o Concept: Only load pages into memory as they are needed (on demand). Pages not currently in use are kept on secondary storage (swap space).

o Benefits:

 Allows programs to be larger than physical memory.

 More processes can run concurrently (increased degree of multiprogramming).

 Less I/O needed to load/swap processes initially.

o Page Fault: An event that occurs when a program tries to access a page that is not currently in main memory.

 Page Fault Handling Steps:

1. Check internal table (for process) to determine if the reference was valid.

2. If invalid, terminate process.

3. If valid but page not in memory:

 Find a free frame.

 Schedule a disk operation to read the desired page into the newly allocated frame.

 Reset page table entry, set validation bit.

 Restart the instruction that caused the page fault.

 Diagram Idea: Flowchart of page fault handling.

• 3.7 Performance of Demand Paging (1 Hour)

o Effective Access Time (EAT): The average time taken to access memory in a demand-paged system.

 EAT = (1 - p) * ma + p * page_fault_time

 p: page-fault rate (0 <= p <= 1)

 ma: memory access time (e.g., 100 ns)

 page_fault_time: time to handle a page fault (can be milliseconds, e.g., 8 ms = 8,000,000 ns). This includes disk latency, transfer time, and CPU overhead.

 Example Calculation:

 Memory access time = 100 ns.

 Average page-fault service time = 8 ms = 8,000,000 ns.

 If page-fault rate p = 0.001 (1 fault per 1000 accesses):

 EAT = (1 - 0.001) * 100 + 0.001 * 8,000,000

 EAT = 0.999 * 100 + 8000 = 99.9 + 8000 = 8099.9 ns (approx 8.1 microseconds).

 Discussion: Even a very low page fault rate can drastically increase EAT due to disk access times. This emphasizes the importance of minimizing page faults.

o Reference String: A sequence of page numbers referenced by a program over time. Used to evaluate page replacement algorithms.

 Example: 1, 2, 3, 4, 1, 2, 5, 1, 2, 3, 4, 5

• 3.8 Page Replacement (1 Hour)

o Concept: When a page fault occurs and no free frame is available, the OS must select a page in memory to replace (swap out) with the new page.

o Goal: To minimize the number of page faults.

o Modified (Dirty) Bit: A bit in the page table entry that indicates whether the page has been modified since it was loaded. If dirty, it must be written back to disk before being replaced. If not dirty, it can just be overwritten.

• 3.9 Page-Replacement Algorithms (0.75 Hour)

o Common Algorithms (with examples using a reference string and a fixed number of frames, e.g., 3 frames):

 First-In, First-Out (FIFO): Replaces the page that has been in memory the longest.

 Example: Reference string 7,0,1,2,0,3,0,4,2,3,0,3,2,1,2,0,1,7,0,1 (3 frames)

 Trace and count page faults.

 Belady's Anomaly: Increasing the number of frames can sometimes lead to more page faults with FIFO.

 Optimal Page Replacement (OPT or MIN): Replaces the page that will not be used for the longest period of time.

 Example: Same reference string.

 Trace and count page faults.

 Fact: This is an ideal algorithm and cannot be implemented in practice (requires knowing the future). Used as a benchmark.

 Least Recently Used (LRU): Replaces the page that has not been used for the longest period of time.

 Example: Same reference string.

 Trace and count page faults.

 Implementation: Requires hardware support (counters or stack of page numbers). Expensive to implement perfectly.

 Approximation Algorithms (Briefly): Discussing practical approximations like:

 Second-Chance (Clock) Algorithm: Uses a reference bit; gives pages a "second chance" before replacement.

 Least Frequently Used (LFU): Replaces page with smallest count.

 Most Frequently Used (MFU): Replaces page with largest count (less common).

• 3.10 Allocation of Frames (0.25 Hour)

o Minimum Number of Frames: Determined by the instruction set architecture (e.g., if an instruction can access multiple memory locations, it needs enough frames to hold all of them).

o Allocation Policies:

 Fixed Allocation: Each process gets a fixed number of frames (e.g., equal share, or proportional to process size).

 Priority Allocation: Processes with higher priority get more frames.

o Global vs. Local Replacement:

 Global Replacement: A process can select a replacement frame from the set of all frames in the system (more common, higher throughput).

 Local Replacement: A process selects a replacement frame only from its own allocated frames (less susceptible to one process's bad behavior).

• 3.11 Thrashing (0.5 Hour)

o Concept: A situation where a process spends more time paging (swapping pages in and out) than executing instructions. Occurs when a process does not have enough frames to hold its actively used pages (its working set).

o Causes: High degree of multiprogramming, insufficient physical memory for the collective working sets of all processes.

o Symptoms: Low CPU utilization, high page fault rate, increased disk activity.

o Working Set Model: The set of pages that a process is actively using at a given time. If Sum(working_set_sizes) > total_frames, thrashing is likely.

o Solving Thrashing:

 Provide more frames.

 Reduce the degree of multiprogramming (suspend/swap out some processes).

 Implement a working-set based page replacement algorithm.

 Pre-paging.

o Diagram Idea: Graph showing CPU utilization dropping significantly as degree of multiprogramming increases beyond an optimal point, illustrating thrashing.

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Part 3: Deadlocks (Approx. 4 Hours)

Objective: To understand the concept of deadlocks, conditions for their occurrence, and various methods to handle them.

• 3.12 System Model (0.5 Hour)

o Resources: Resources are entities used by processes. Can be hardware (CPU cycles, memory, I/O devices) or software (files, locks, semaphores).

o Resource Types: Each resource type has a certain number of identical instances (e.g., 3 printers, 1 CPU).

o Process Uses Resources in Sequence:

1. Request: Process requests a resource.

2. Use: Process uses the resource.

3. Release: Process releases the resource.

o Example: A system with two printers and two processes. P1 needs printer 1, then printer 2. P2 needs printer 2, then printer 1.

• 3.13 Deadlock Characterization (1 Hour)

o Definition: A set of blocked processes, each holding a resource and waiting to acquire a resource held by another process in the set.

o Necessary Conditions for Deadlock (all four must hold simultaneously):

1. Mutual Exclusion: At least one resource must be held in a non-sharable mode (only one process can use it at a time).

2. Hold and Wait: A process must be holding at least one resource and waiting to acquire additional resources held by other processes.

3. No Preemption: A resource can only be released voluntarily by the process holding it, after that process has completed its task.

4. Circular Wait: A set of processes {P0,P1,…,Pn} exists such that P0 is waiting for a resource held by P1, P1 is waiting for a resource held by P2, ..., Pn is waiting for a resource held by P0.

o Resource-Allocation Graph: A directed graph used to describe deadlocks.

 Nodes: Processes (circles), Resource types (squares).

 Edges:

 Request Edge: Directed edge from process to resource type (Pi→Rj).

 Assignment Edge: Directed edge from resource type to process (Rj→Pi).

 Diagram Idea: Examples of graphs with and without deadlocks, and a graph showing a circular wait.

 Fact: If the graph has no cycles, then no deadlock. If the graph has a cycle:

 If only one instance per resource type, then deadlock exists.

 If multiple instances per resource type, then deadlock may exist.

• 3.14 Methods for Handling Deadlocks (0.5 Hour)

o Options:

0. Deadlock Prevention: Ensure that at least one of the four necessary conditions cannot hold.

1. Deadlock Avoidance: Give the OS enough information so it can avoid deadlocks by making careful resource allocation decisions.

2. Deadlock Detection and Recovery: Allow deadlocks to occur, detect them, and then recover.

3. Ignore the Problem: Assume deadlocks never occur (used by most OSes, including Linux and Windows, for simplicity and performance, relying on user diligence and rare occurrence).

• 3.15 Deadlock Prevention (1 Hour)

o Breaking Mutual Exclusion:

 Make resources sharable (e.g., read-only files). Not always possible (e.g., printers).

o Breaking Hold and Wait:

 Option 1: Process requests all resources it needs at once. If all available, granted; otherwise, wait.

 Disadvantages: Low resource utilization, possible starvation.

 Option 2: Process must release all held resources before requesting new ones.

 Disadvantages: May need to repeatedly acquire and release same resources.

o Breaking No Preemption:

 If a process holding resources requests another that cannot be immediately allocated, it must release all currently held resources.

 Preempted resources are added to the list of resources for which the process is waiting.

 Only practical for resources whose state can be easily saved and restored (e.g., CPU registers, not printers).

o Breaking Circular Wait:

 Impose a total ordering of all resource types. Processes must request resources in increasing order of enumeration.

 Example: Resources R1, R2, R3. Order: R1 < R2 < R3.

 A process requesting R2 cannot then request R1.

 Advantages: Simple to implement.

 Disadvantages: May lead to low resource utilization, hard to define the optimal ordering.

• 3.16 Deadlock Avoidance (0.5 Hour)

o Concept: The OS requires prior information about the resources a process will request and release. It then dynamically checks if granting a request would lead to an unsafe state.

o Safe State: A state is safe if there exists a safe sequence of all processes such that for each process Pi, the resources that Pi can still request can be satisfied by currently available resources plus resources held by all Pj (where j < i).

o Unsafe State: A state that is not safe. An unsafe state may lead to deadlock, but not necessarily.

o Fact: Deadlock avoidance is less restrictive than prevention.

o Banker's Algorithm (Dijkstra):

 Purpose: For a single instance of each resource type, or multiple instances.

 Data Structures:

 Available: Vector of length m (number of resource types).

 Max: n x m matrix (max demand of each process).

 Allocation: n x m matrix (current allocation to each process).

 Need: n x m matrix (Max - Allocation).

 Safety Algorithm: Determines if the current state is safe.

 Resource-Request Algorithm: Determines if a request can be safely granted.

 Example: Provide a simple numerical example of Banker's Algorithm with a few processes and resource types to illustrate finding a safe sequence.

 Drawbacks: Requires prior knowledge of max resource needs, processes don't always release resources when done, number of processes is not fixed, resources can fail.

• 3.17 Deadlock Detection (0.5 Hour)

o Concept: Allow deadlocks to occur, then periodically run an algorithm to detect if a deadlock has occurred.

o Detection Algorithm: Similar to the safety algorithm in Banker's, but uses Current Allocation and Remaining Request to find if any process can complete. If no process can complete, and there are blocked processes, then a deadlock exists.

o Fact: Detection involves overhead. Frequency depends on how often deadlocks are expected and how quickly recovery is needed.

o When to run detection? Every resource request, or periodically, or when CPU utilization drops below a threshold.

• 3.18 Recovery from Deadlock (0.5 Hour)

o Once a deadlock is detected, a recovery mechanism is needed.

o Process Termination:

 Terminate all deadlocked processes: Simple but drastic.

 Terminate one process at a time until deadlock is eliminated: More efficient, but requires identifying which process to terminate.

 Selection Criteria: Priority, how long process has computed, resources used, resources needed, process interactive or batch.

o Resource Preemption:

 Select a victim: Which resources to preempt from which process.

 Rollback: Return the process to some safe state and restart it from that state. Difficult to implement accurately.

 Starvation: Ensure that the same process is not always picked as a victim.

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General Considerations for UNIT-III:

• Complexity: These are highly conceptual and often challenging topics. Break them down, use clear analogies.

• Visual Aids: Diagrams are absolutely essential for Memory Management (MMU, fragmentation, segmentation, paging, TLB) and Deadlocks (resource-allocation graphs).

• Numerical Examples: Critical for Paging (EAT, page replacement algorithms) and Deadlocks (Banker's Algorithm, detection). Work through them step-by-step.

• Interaction: Encourage students to draw diagrams and work through examples themselves.

• Real-world Context: Briefly mention how these concepts are applied in modern OS (e.g., Linux uses demand paging, specific scheduling algorithms, often ignores deadlocks in general systems, but critical systems might use avoidance).

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Please let me know if you'd like me to proceed with the detailed content for UNIT-IV (Information Management and Linux File Security)!