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[ Option B ]

The fork() System Call
The fork() system call in C is used to create a new process by duplicating the existing one.
After a fork() call, there are two processes running the same code, the parent process and the child process. Each process continues execution from the point where the fork() was called. So, if you call fork() multiple times, the number of processes increases exponentially.

There is no loop, and each fork() doubles the number of processes. Hence, total “Hello” prints = 2^{number of forks} 
Finally, 2² = 4.
 

[ Option C ]

A Race Condition occurs when two or more threads or processes try to access and modify the same shared resource (like an object) at the same time without proper synchronization. This leads to unpredictable and incorrect behavior.
For instance, if three threads attempt to share and modify a single object concurrently, and there is no mechanism to control access (like locks or mutex), a race condition occurs causing data corruption or inconsistent results.

[ Option D ]

The MacOS (formerly OS X) uses the XNU kernel, which is a hybrid kernel. This kernel architecture combines features from both the microkernel and monolithic kernel designs.

[ Option C ]

An Operating System (OS) is a system software that acts as an interface between the user and the computer hardware. It manages hardware resources and provides essential services for running applications.

[ Option B ]

The File System in an Operating System (OS) provides a way to store, organize, and manage files on storage devices. It allows the system to:

• Create and delete files.
• Organize files into directories and folders.
• Control access and provide protection from unauthorized users.
• Maintain metadata like file size, type, timestamps and permissions.

[ Option C ]

When a computer is powered on, the BIOS (Basic Input/Output System) is responsible for initializing hardware, performing system checks, and loading the operating system into main memory so that the computer can start functioning.

[ Option D ]

An OS has several key components, each responsible for managing a specific part of the computer:

1. The File System Manager is the component of an operating system responsible for managing files. It handles the creation, deletion, organization, access control, and storage allocation for files on storage devices.
2. The Memory Manager handles the management of system memory (RAM), allocating and deallocating space to processes.
3. The Process Manager controls processes, including their creation, scheduling, and termination.
4. The Device Driver acts as an interface between the operating system and hardware devices, managing device control and communication.

[ Option D ]

A Process is a program in execution. When a program is loaded into memory for execution, the OS assigns it various attributes to help manage and control it effectively. These attributes are part of the Process Control Block (PCB), which contains all the important information about a running process.

[ Option A ]

A Binary File stores data in machine-readable format using binary digits (bits), which are 0s and 1s. These digits represent the on and off states in digital circuits, making it a format that computers can directly read and process.

Unlike Text Files which store alphabets, numbers, and special characters in readable format, binary files store data in a very compact and efficient way using only 0s and 1s.

[ Option D ]

A SPOOLER is special system software used to manage and create a job queue. It stands for Simultaneous Peripheral Operations On-Line. The spooler collects jobs  and stores them in a queue (FIFO), then executes them one by one in order, ensuring efficient use of resources. The spooler ensures jobs are executed in the correct order without conflicts or loss.

[ Option B ]

NTFS (New Technology File System) is the main file system used by Windows operating systems to store and organize data on hard drives. It is more advanced than FAT and FAT32 because it supports features like file permissions, encryption, compression, and large storage sizes.
An NTFS volume layout is divided into several main components that define how data is stored and accessed:

There is no component called “Master bytes” in the NTFS layout.

[ Option C ]

A Deadlock is a situation in an operating system where two or more processes are waiting for each other indefinitely to release resources. For a deadlock to occur, four necessary conditions (Coffman’s conditions) must hold simultaneously.

Deadlock happens only when resources cannot be pre-empted. Therefore, Pre-emption itself is not a condition for deadlock. In fact, it helps prevent deadlock.

[ Option D ]

Swapping is a memory management technique used when the system’s main memory (RAM) becomes full. 
In a multitasking environment, several processes are loaded into memory, but sometimes there is not enough space for all of them. To handle this, the operating system temporarily moves some inactive processes from main memory to the hard disk (swap space). This process is called swapping out.

When the process is needed again, it is swapped back into memory, called swapping in. This allows the OS to manage limited memory more efficiently and ensures that active processes get enough memory to run.

[ Option C ]

A Thread is a lightweight unit of a process that allows multiple parts of a program to execute concurrently. There are two main types of threads.

1. User-Level Threads (ULTs).
2. Kernel-Level Threads (KLTs).

User-Level Threads (ULTs): 

• These threads are managed entirely by user-level thread libraries, not by the operating system kernel. 
• The thread creation, scheduling, and synchronization are handled in user space, which makes them faster and more efficient since no system calls are needed.
• If one user-level thread is blocked, the entire process gets blocked because the kernel is unaware of individual threads.

Kernel-Level Threads (KLTs):

• These threads are managed directly by the operating system kernel. Each thread is known to the OS, and the kernel handles scheduling and management. 
• This allows true parallel execution on multiprocessor systems, as the OS can assign different threads to different CPUs. 
• Creating and switching between kernel threads is slower because it involves System Calls and more overhead.
   

[ Option C ]

The Program Counter (PC) is a special register in the CPU that stores the address of the next instruction to fetch and execute from memory.
After fetching the current instruction, the PC increments to point to the next instruction’s address unless modified by a jump or branch instruction.
This allows the CPU to execute the sequence of instructions in order and supports control flow changes.

[ Option A ]

System Calls are special functions provided by the OS that allow user programs to request services from the kernel, such as process creation, file handling, or communication. 
In process management, three important system calls are fork(), wait(), and exec(), each serving a specific purpose in process control.

[ Option D ]

Operating systems handle a variety of errors that may arise during process execution or hardware interaction.
Lack of paper in printer, the OS detects and handles this by notifying the user or pausing the printing process until paper is available.
Connection failure in the network, the OS manages network errors by detecting connection failures, reporting issues, and attempting reconnections or switching to backup networks.
Power failure, the OS can handle power failures by initiating safe shutdown procedures, saving unsaved data, and preserving system integrity through battery backups or power management features.

[ Option B ]

Multithreading OS refers to operating systems that support multiple threads within a single process to improve efficiency. Basically, multithreading is a feature of modern OS.
Multiprogramming OS allows multiple programs to run on a computer at the same time by managing CPU time effectively.
Multitasking OS lets users run multiple applications simultaneously by rapidly switching between tasks.

[ Option A ]

Round Robin (RR) is a preemptive CPU scheduling algorithm used in operating systems.

• In RR, each process is assigned a fixed time slice (quantum) for execution.
• If a process does not finish in its time quantum, it is preempted and moved to the end of the ready queue, allowing the next process to execute.
• This ensures fair CPU allocation among all processes and is commonly used in time-sharing systems.

CPU Scheduling is the method by which an operating system decides which process in the ready queue will get the CPU next. The main goal is to maximize CPU utilization, minimize waiting time, and ensure fair access to processes. The CPU scheduling mainly two types:

1. Preemptive Scheduling : The CPU can be taken away from a running process if a higher-priority process arrives or its time quantum expires.
   • Examples:
   • Round Robin (RR).
   • Shortest Remaining Time First (SRTF).
   • Priority Scheduling (Preemptive).
2. Non-Preemptive Scheduling : Once a process starts execution, it cannot be interrupted until it finishes or voluntarily yields the CPU.
   • Examples:
   • First-Come, First-Served (FCFS).
   • Shortest Job Next (SJN) / Shortest Job First (SJF).
   • Priority Scheduling (Non-Preemptive).

[ Option D ]

In memory management, different techniques are used to load and manage processes in main memory.

• In Simple Segmentation, a process is divided into segments like code, data, and stack, and all of them are loaded into dynamic memory partitions, which do not have to be next to each other.
• In Virtual Memory Paging, a process is divided into fixed-size pages, but not all pages are loaded at once, only the needed pages are brought into memory later.
• In Virtual Memory Segmentation, a process is divided into segments, and only the required ones are loaded when needed, similar to virtual paging.
• In Simple Paging, all the pages of a process are loaded into available frames, even if those frames are not contiguous.

[ Option B ]

FIFO (First In First Out) is a scheduling or data handling method where the first process or item that enters the queue is the first one to be processed or removed. It works much like a queue where the earliest request is served before others.

[ Option D ]

In an Operating System (OS), a process is a program in execution. Each process moves through various states during its life cycle, from creation to termination. Typically, a process can exist in five main states.

[ Option B ]

The /proc file system in Linux is a virtual file system that provides information about the system’s processes and kernel in real time. It does not exist on the disk like regular files, instead, it resides in kernel memory and is generated dynamically when accessed.
The /proc directory contains files and folders that represent system information such as CPU usage, memory details, running processes, and kernel parameters.

[ Option C ]

When a process fails, most operating systems record the error information in a log file. This log file serves as a permanent record to help system administrators, developers, and support personnel diagnose and troubleshoot problems.

By recording details such as the time of failure, type of error, and sometimes even a memory dump, log files help developers and administrators trace the cause of the failure. This approach provides a reliable and centralized way to analyze problems and ensure system stability.

[ Option B ]

The Kernel is the core part of an operating system that permanently resides in main memory (RAM).

• It manages system resources, CPU scheduling, memory management, I/O operations, and communication between hardware and software.
• All other parts of the OS rely on the kernel to perform basic functions and ensure smooth operation of the system.

[ Option C ]

An INI file (initialization file (.ini)) in Windows 95 is a plain text configuration file used to store settings and configuration data for the operating system and applications. These files are organized into sections containing key-value pairs and are readable and editable using any text editor like Notepad.