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(1) GUI stands for .
--> Graphical User Interface.

(2) Queue at Ticket window is example of __________ type of scheduling algorithm.
--> FCFS (First-Come, First-Served).

(3) What is the full form of PCB?
--> Process Control Block.

(1) Explain Context Switching.
--> Context switching is the procedure of storing the state (or context) of an active process or thread so that it can be paused and later resumed from the exact point it was stopped. This mechanism enables multiple processes to share a single CPU efficiently, making multitasking possible in operating systems. The state of the process is saved in its Process Control Block (PCB).

(1) Explain SJF with suitable example.
--> * EXPLANATION:

- Shortest Job First (SJF) is a scheduling algorithm in which the process with the smallest execution time (burst time) is selected for execution next.

- It can be either preemptive (Shortest Remaining Time First) or non-preemptive.

- SJF is highly efficient as it minimizes the average waiting time for the batch of processes.

 * EXAMPLE (Non-preemptive):
   Suppose we have 4 processes arriving at time 0 with different burst times:
   
   Process | Burst Time
   --------------------
      P1   |     6
      P2   |     8
      P3   |     7
      P4   |     3

   Order of Execution (based on shortest burst time):
   1st: P4 (Burst time 3)
   2nd: P1 (Burst time 6)
   3rd: P3 (Burst time 7)
   4th: P2 (Burst time 8)

   Gantt Chart Representation:
   | P4 |  P1  |   P3   |    P2    |
   0    3      9        16         24

   Calculation of Waiting Time:
   Wait time for P4 = 0
   Wait time for P1 = 3
   Wait time for P3 = 9
   Wait time for P2 = 16
   Average Waiting Time = (0 + 3 + 9 + 16) / 4 = 28 / 4 = 7 units

OR

(1) Define an Operating System.
--> An Operating System (OS) is system software that manages computer hardware, software resources, and provides common services for computer programs. It acts as an intermediary between the user and the computer hardware.

(2) When running process requires some input/output then it goes to _______ state.
--> waiting (or blocked) state.

(3) What is Process?
--> A process is a program in execution. While a program is a passive entity (a file containing a list of instructions stored on disk), a process is an active entity with a program counter specifying the next instruction to execute and a set of associated resources.

(1) Explain Process state transition diagram in brief.
--> The process state transition diagram illustrates the lifecycle of a process as it moves through various states during its execution. The five primary states are:

1. New: The process is being created.
2. Ready: The process is waiting to be assigned to a processor.
3. Running: Instructions are being executed by the CPU.
4. Waiting (or Blocked): The process is waiting for some event to occur (such as an I/O completion or reception of a signal).
5. Terminated: The process has finished execution.

(1) Explain FCFS with suitable example.
--> * EXPLANATION:

- First-Come, First-Served (FCFS) is the simplest CPU scheduling algorithm. Processes are allocated the CPU in the exact order they arrive in the ready queue.

- It is a non-preemptive algorithm, meaning once a process gets the CPU, it keeps it until it terminates or requests I/O.

- While easy to implement using a FIFO (First-In-First-Out) queue, it can suffer from the "Convoy Effect," where short processes get stuck waiting for a long process to finish, increasing the average waiting time.

 * EXAMPLE:
   Suppose 3 processes arrive at time 0 in the order P1, P2, P3.
   
   Process | Burst Time
   --------------------
      P1   |     24
      P2   |     3
      P3   |     3

   Order of Execution: P1 -> P2 -> P3

   Gantt Chart Representation:
   |            P1            | P2 | P3 |
   0                          24   27   30

   Calculation of Waiting Time:
   Wait time for P1 = 0
   Wait time for P2 = 24
   Wait time for P3 = 27
   Average Waiting Time = (0 + 24 + 27) / 3 = 51 / 3 = 17 units

(1) Define deadlock.
--> A deadlock is a situation in an operating system where a set of processes are permanently blocked because each process is holding a resource and waiting to acquire a resource held by another process in the set.

(2) What is External fragmentation?
--> External fragmentation occurs when the total memory space available to satisfy a request is sufficient, but it is not contiguous (it is divided into small, separate blocks scattered throughout memory), preventing the allocation.

(3) Explain the concept of paging.
--> Paging is a memory management technique that allows the physical address space of a process to be non-contiguous. It divides physical memory into fixed-size blocks called "frames" and logical memory into blocks of the same size called "pages," simplifying memory allocation and avoiding external fragmentation.

(1) Explain deadlock prevention techniques.
--> Deadlock prevention ensures that a deadlock cannot occur by denying at least one of the four necessary conditions:
1. Mutual Exclusion: Use sharable resources whenever possible so processes don't have to wait.
2. Hold and Wait: Require processes to request all needed resources at once before execution.
3. No Preemption: Allow the OS to forcefully take away resources from a process if it requests another resource that is currently unavailable.
4. Circular Wait: Impose a strict numerical ordering on all resource types and require processes to request resources in increasing order.

(1) Describe contiguous and non-contiguous memory allocation.
--> * EXPLANATION:

1. Contiguous Memory Allocation:
- In this scheme, each process is allocated a single contiguous block of physical memory.
- It is simpler to implement and faster to execute because the entire process is in one location.
- Drawback: It suffers from external fragmentation, leaving unused holes in memory.

2. Non-Contiguous Memory Allocation:
- A process is divided into multiple parts, and these parts are placed in different, non-adjacent blocks of physical memory.
- It utilizes memory efficiently and solves the external fragmentation problem.
- Drawback: Slower access time and requires overhead for address translation (like page tables).
- Examples: Paging and Segmentation.

OR

(1) In Paging, we divide the programs into equal sized blocks called ________ and the main memory is Divided into equal sized blocks known as _________.
--> pages, frames.

(2) What is internal Fragmentation?
--> Internal fragmentation occurs when a memory block assigned to a process is larger than the memory requested by the process. The unused space within that allocated block is wasted and cannot be used by other processes.

(3) Full form of SMT ________________.
--> Simultaneous Multithreading.

(1) What is the difference between paging and segmentation?
-->
Paging: Divides logical memory into fixed-size blocks (pages). It is invisible to the user and is primarily a hardware mechanism used to avoid external fragmentation.
Segmentation: Divides logical memory into variable-size blocks (segments) based on the logical structure of the program (e.g., functions, arrays). It is visible to the user and makes handling growing data structures easier.

(1) Explain physical memory and Virtual Memory.
--> * EXPLANATION:

Physical Memory:
- Physical memory refers to the actual RAM (Random Access Memory) installed on the motherboard of the computer.
- It is volatile memory where currently running programs and data are stored for quick access by the CPU.
- The size of physical memory is strictly limited by the hardware installed.

Virtual Memory:
- Virtual memory is a memory management technique that creates an illusion for users of a very large (main) memory.
- The OS maps memory addresses used by a program (virtual addresses) into physical addresses in computer memory.
- It works by using a portion of secondary storage (like a hard drive or SSD) as an extension of physical RAM.
- When RAM is full, the OS moves data that hasn't been used recently to the disk (swapping/paging), freeing up RAM for active processes. This allows executing programs that are larger than the available physical memory.

(1) Who Developed Unix?
--> Unix was developed by Ken Thompson and Dennis Ritchie (along with others) at AT&T's Bell Labs in the late 1960s and early 1970s.

(2) What is the extension for a shell script file?
--> .sh

(3) Name any two Unix file system types.
--> 1. ext4 (Fourth Extended File System)
2. XFS (eXtended File System)

(1) Explain Different types of shells in Unix.
--> A shell is a command-line interpreter that provides an interface between the user and the kernel. Common types include:
1. Bourne Shell (sh): The original Unix shell, known for its speed and compactness.
2. C Shell (csh): Designed to have a syntax similar to the C programming language and introduced command history.
3. Korn Shell (ksh): Combines features of both the Bourne shell and C shell, offering better scripting capabilities.
4. Bourne Again Shell (bash): The default shell for most Linux distributions, an enhanced replacement for the Bourne shell.

(1) Write a short note on VI Editor.
--> * EXPLANATION:

- The vi (Visual) editor is a powerful, screen-oriented text editor originally created for the Unix operating system.
- It is universally available on almost all Unix and Linux systems.
- The vi editor operates entirely using the keyboard and is known for its efficiency once the commands are mastered.

- Modes of VI Editor:
1. Command Mode: This is the default mode when vi starts. Keystrokes are interpreted as commands (e.g., to copy, paste, delete lines, or navigate). You cannot type text in this mode.
2. Insert Mode: In this mode, text can be typed and inserted into the file. You enter this mode by pressing keys like 'i' (insert), 'a' (append), or 'o' (open new line).
3. Last Line (Command-line) Mode: Accessed by typing a colon ':' in command mode. Used for saving the file, exiting, or performing global substitutions.

- Basic Commands:
- `i` : Switch to Insert mode.
- `Esc` : Return to Command mode.
- `:wq` or `:x` : Save and quit.
- `:q!` : Quit without saving.

OR

(1) The Bourne shell written by?
--> Stephen Bourne.

(2) BASH Stands for____________.
--> Bourne Again SHell.

(3) How many Types of Permission in Linux?
--> Three main types: Read (r), Write (w), and Execute (x).

(1) Explain Following Command: - Cat - ls
-->
cat (concatenate): Used to read data from a file and output its contents to the terminal screen. It is frequently used to display the contents of short text files or combine multiple files together. (e.g., `cat filename.txt`)

ls (list): Used to list the files and directories contained within the current working directory. It provides various options like `-l` for a detailed long format or `-a` to show hidden files. (e.g., `ls -l`)

(1) Explain Pattern Matching command in Linux.
--> * EXPLANATION:

- In Linux, the primary command used for pattern matching is grep (Global Regular Expression Print).
- The `grep` command searches through files or standard input for lines containing a match to a specified string or regular expression pattern.
- When it finds a matching line, it prints that line to the standard output (the terminal screen) by default.

- Basic Syntax:
`grep [options] pattern [file_name]`

- Common Options:
- `-i` : Ignores case sensitivity (matches both uppercase and lowercase).
- `-v` : Inverts the match (prints lines that do NOT match the pattern).
- `-c` : Counts the number of matching lines instead of printing them.
- `-n` : Displays the matched lines along with their line numbers.

 * EXAMPLES:
   1. Search for the word "error" in a file named syslog.txt:
      grep "error" syslog.txt

   2. Search for "failed" case-insensitively in auth.log:
      grep -i "failed" auth.log

(1) What is Shell Variables?
--> Shell variables are character strings to which we assign a value. The value assigned can be a number, text, filename, or any other type of data. They are used by the shell to store information temporarily during the execution of a script or session.

(2) Name two shell keywords.
--> 1. if
2. for

(3) Explain test command.
--> The test command in Linux/Unix is used to evaluate conditional expressions, such as checking file types, file permissions, and comparing strings or numbers. It returns an exit status of 0 if the expression is true, and 1 if it is false. It is often used inside if statements.

(1) Explain Positional Parameters.
--> Positional parameters are special variables in shell scripting that hold the arguments passed to a script or a function when it is executed.

They are represented by numbers: $1 is the first argument, $2 is the second, and so on up to $9. The variable $0 holds the name of the script itself, and $# holds the total number of arguments passed.

(1) Write a shell script to Display a Digital Clock.
--> * EXPLANATION:

- To create a digital clock in a shell script, we use an infinite while loop.
- Inside the loop, the clear command is used to clear the terminal screen so the clock updates in the same spot.
- The date +%T command retrieves the current system time in HH:MM:SS format.
- The sleep 1 command pauses the loop for one second before refreshing, creating the ticking effect.

 * SCRIPT CODE:
   #!/bin/bash
   
   # Infinite loop to keep the clock running
   while true
   do
       # Clear the screen
       clear
       
       # Print the current time in HH:MM:SS format
       echo "======================="
       echo "     DIGITAL CLOCK     "
       echo "======================="
       date +%T
       echo "======================="
       
       # Pause the script for 1 second
       sleep 1
   done

OR

(1) Which directory contains system configuration files processors?
--> The /etc directory contains all the system-wide configuration files in a Unix/Linux operating system.

(2) How many Types of Looping Structure in Linux?
--> There are three main types of looping structures in Linux shell scripting:
1. for loop
2. while loop
3. until loop

(3) What is system variable?
--> System variables (also known as Environment Variables) are predefined variables created and maintained by the operating system or the shell itself. They are used to configure the computing environment and are typically written in uppercase (e.g., $HOME, $PATH, $USER).

(1) Explain decision statements in UNIX.
--> Decision statements (or conditional statements) in UNIX allow a script to execute different blocks of code based on certain conditions. The two primary decision statements are:
1. if-else statements: Evaluates a condition and executes a block of code if the condition is true. An optional else or elif block handles false conditions.
2. case statement: A multi-way branching statement that compares a variable against several patterns and executes the corresponding block of code when a match is found. It is an efficient alternative to multiple if-elif statements.

(1) Explain Nano Editor.
--> * EXPLANATION:

- Nano is a simple, lightweight, and user-friendly command-line text editor for Unix-like operating systems.
- Unlike the vi editor, which has multiple modes (command, insert), nano is a "modeless" editor, meaning you can start typing text immediately upon opening it.
- It is highly favored by beginners because it displays an on-screen menu of available keyboard shortcuts at the bottom of the terminal window.

- Key Features:
- Syntax highlighting for various programming languages.
- Search and replace functionality.
- Auto-indentation and word wrapping.

- Basic Shortcuts (Uses the Ctrl key, represented by ^):
- ^O (Ctrl + O): Save the file (Write Out).
- ^X (Ctrl + X): Exit the editor.
- ^W (Ctrl + W): Search for a string (Where Is).
- ^K (Ctrl + K): Cut a line of text.
- ^U (Ctrl + U): Paste (Uncut) a line of text.

(1) GPL Stands For ____________.
--> General Public License (or GNU General Public License).

(2) Write syntax to add user to particular group.
--> usermod -aG group_name user_name

(3) The UFW is an acronym for _________.
--> Uncomplicated Firewall.

(1) Explain the difference between LILO and GRUB.
-->
LILO (LInux LOader): An older bootloader that does not understand file systems. It relies on mapping the physical block locations of the kernel on the hard drive. If you update the kernel or change its location, you must reinstall LILO to update the block map.

GRUB (GRand Unified Bootloader): A modern, more advanced bootloader that understands file systems. It can read the kernel file directly from the filesystem without needing physical block locations. It also provides an interactive command-line interface for troubleshooting during boot.

(1) Explain the installation and configuration of a Samba server.
--> * EXPLANATION:

- Samba is a software suite that allows Linux/Unix machines to seamlessly share files and printers with Windows systems over a network using the SMB/CIFS protocol.

Installation Steps (Debian/Ubuntu-based):
1. Update the package list: sudo apt update
2. Install the Samba package: sudo apt install samba

Configuration Steps:
1. The main configuration file is located at /etc/samba/smb.conf.
2. Open the file in an editor (e.g., nano or vi): sudo nano /etc/samba/smb.conf
3. Add a new directory share at the bottom of the file:

      [SharedFolder]
      path = /home/username/shared
      available = yes
      valid users = username
      read only = no
      browsable = yes
      public = yes
      writable = yes

4. Save and exit the file.
5. Create a Samba password for the user: sudo smbpasswd -a username
6. Restart the Samba service to apply changes: sudo systemctl restart smbd

OR

(1) Full form Of UFW _____________.
--> Uncomplicated Firewall.

(2) Wine stands for __________.
--> Wine Is Not an Emulator.

(3) List the Special three section of the smb.conf file.
--> The three special sections are: [global], [homes], and [printers].

(1) Explain firewall and how to enable firewall in Linux.
--> A firewall is a network security system that monitors and controls incoming and outgoing network traffic based on predetermined security rules. It establishes a barrier between a trusted internal network and an untrusted external network (like the Internet).

In Linux (specifically Ubuntu/Debian), you can enable the Uncomplicated Firewall (UFW) using the command line:
sudo ufw enable
To check its status, use:
sudo ufw status

(1) Describe the installation and working of an Apache server in Linux.
--> * EXPLANATION:

- Apache HTTP Server is one of the most widely used open-source web servers in the world. It delivers web content (HTML pages, multimedia) through the internet.

Installation (Debian/Ubuntu-based):
1. Update repositories: sudo apt update
2. Install Apache: sudo apt install apache2
3. Start the service: sudo systemctl start apache2
4. Enable it to run on boot: sudo systemctl enable apache2

Working of Apache:
- Once installed, Apache continuously runs in the background as a daemon process.
- It listens for incoming HTTP (Port 80) and HTTPS (Port 443) requests from client web browsers.
- When a request is received, Apache processes it, locates the requested file (usually located in the default root directory /var/www/html/), and sends the file back to the client's browser over the network.
- Configuration files, like /etc/apache2/apache2.conf, allow administrators to set up virtual hosts, manage access controls, and load dynamic modules (like PHP support).
[Image of Apache Web Server working architecture diagram]

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Thursday, 12 March 2026

OS | PAPER

(1) GUI stands for .
--> Graphical User Interface.

(2) Queue at Ticket window is example of __________ type of scheduling algorithm.
--> FCFS (First-Come, First-Served).

(3) What is the full form of PCB?
--> Process Control Block.

 * EXAMPLE (Non-preemptive):
   Suppose we have 4 processes arriving at time 0 with different burst times:
   
   Process | Burst Time
   --------------------
      P1   |     6
      P2   |     8
      P3   |     7
      P4   |     3

   Order of Execution (based on shortest burst time):
   1st: P4 (Burst time 3)
   2nd: P1 (Burst time 6)
   3rd: P3 (Burst time 7)
   4th: P2 (Burst time 8)

   Gantt Chart Representation:
   | P4 |  P1  |   P3   |    P2    |
   0    3      9        16         24

   Calculation of Waiting Time:
   Wait time for P4 = 0
   Wait time for P1 = 3
   Wait time for P3 = 9
   Wait time for P2 = 16
   Average Waiting Time = (0 + 3 + 9 + 16) / 4 = 28 / 4 = 7 units

OR

(2) When running process requires some input/output then it goes to _______ state.
--> waiting (or blocked) state.

 * EXAMPLE:
   Suppose 3 processes arrive at time 0 in the order P1, P2, P3.
   
   Process | Burst Time
   --------------------
      P1   |     24
      P2   |     3
      P3   |     3

   Order of Execution: P1 -> P2 -> P3

   Gantt Chart Representation:
   |            P1            | P2 | P3 |
   0                          24   27   30

   Calculation of Waiting Time:
   Wait time for P1 = 0
   Wait time for P2 = 24
   Wait time for P3 = 27
   Average Waiting Time = (0 + 24 + 27) / 3 = 51 / 3 = 17 units

OR

(1) In Paging, we divide the programs into equal sized blocks called ________ and the main memory is Divided into equal sized blocks known as _________.
--> pages, frames.

(3) Full form of SMT ________________.
--> Simultaneous Multithreading.

(1) Who Developed Unix?
--> Unix was developed by Ken Thompson and Dennis Ritchie (along with others) at AT&T's Bell Labs in the late 1960s and early 1970s.

(2) What is the extension for a shell script file?
--> .sh

(3) Name any two Unix file system types.
--> 1. ext4 (Fourth Extended File System)
2. XFS (eXtended File System)

OR

(1) The Bourne shell written by?
--> Stephen Bourne.

(2) BASH Stands for____________.
--> Bourne Again SHell.

(3) How many Types of Permission in Linux?
--> Three main types: Read (r), Write (w), and Execute (x).

 * EXAMPLES:
   1. Search for the word "error" in a file named syslog.txt:
      grep "error" syslog.txt

   2. Search for "failed" case-insensitively in auth.log:
      grep -i "failed" auth.log

(2) Name two shell keywords.
--> 1. if
2. for

 * SCRIPT CODE:
   #!/bin/bash
   
   # Infinite loop to keep the clock running
   while true
   do
       # Clear the screen
       clear
       
       # Print the current time in HH:MM:SS format
       echo "======================="
       echo "     DIGITAL CLOCK     "
       echo "======================="
       date +%T
       echo "======================="
       
       # Pause the script for 1 second
       sleep 1
   done

OR

(1) Which directory contains system configuration files processors?
--> The /etc directory contains all the system-wide configuration files in a Unix/Linux operating system.

(2) How many Types of Looping Structure in Linux?
--> There are three main types of looping structures in Linux shell scripting:
1. for loop
2. while loop
3. until loop

(1) GPL Stands For ____________.
--> General Public License (or GNU General Public License).

(2) Write syntax to add user to particular group.
--> usermod -aG group_name user_name

(3) The UFW is an acronym for _________.
--> Uncomplicated Firewall.

      [SharedFolder]
      path = /home/username/shared
      available = yes
      valid users = username
      read only = no
      browsable = yes
      public = yes
      writable = yes

4. Save and exit the file.
5. Create a Samba password for the user: sudo smbpasswd -a username
6. Restart the Samba service to apply changes: sudo systemctl restart smbd

OR

(1) Full form Of UFW _____________.
--> Uncomplicated Firewall.

(2) Wine stands for __________.
--> Wine Is Not an Emulator.

(3) List the Special three section of the smb.conf file.
--> The three special sections are: [global], [homes], and [printers].

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Thursday, 12 March 2026

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