1What is the primary objective of an Operating System?
A.To replace the need for RAM
B.To make the hardware run faster
C.To provide an environment for a user to execute programs conveniently and efficiently
D.To compile source code into machine code
Correct Answer: To provide an environment for a user to execute programs conveniently and efficiently
Explanation:
An operating system acts as an intermediary between the user and the computer hardware, aiming to make the system convenient to use and efficient in operation.
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2Which bit in the PSW (Program Status Word) register distinguishes between User Mode and Supervisor (Kernel) Mode?
A.Mode bit
B.Flag bit
C.Status bit
D.Interrupt bit
Correct Answer: Mode bit
Explanation:
The mode bit is used in hardware to indicate the current mode: 0 for kernel/monitor mode and 1 for user mode.
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3Privileged instructions can only be executed in which mode?
A.Both User and Supervisor Mode
B.User Mode
C.I/O Mode
D.Supervisor Mode
Correct Answer: Supervisor Mode
Explanation:
Privileged instructions, which can cause harm if misused (like I/O control or memory management), are restricted to Supervisor (Kernel) Mode.
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4What is the main disadvantage of a Simple Batch System?
A.CPU remains idle during I/O operations
B.Complex user interface
C.Lack of security
D.High cost of implementation
Correct Answer: CPU remains idle during I/O operations
Explanation:
In simple batch systems, the CPU sits idle while a job performs I/O operations because only one job is processed at a time.
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5Which system concept increases CPU utilization by organizing jobs so that the CPU always has one to execute?
A.Distributed Processing
B.Batch Processing
C.Multiprogramming
D.Single-tasking
Correct Answer: Multiprogramming
Explanation:
Multiprogramming keeps several jobs in memory simultaneously. When one job waits for I/O, the OS switches to another job to keep the CPU busy.
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6What is the defining characteristic of a Time-Sharing System (Multitasking)?
A.It switches the CPU between jobs so frequently that users can interact with each program while it is running
B.It uses multiple CPUs
C.It executes jobs strictly sequentially
D.It is designed only for batch jobs
Correct Answer: It switches the CPU between jobs so frequently that users can interact with each program while it is running
Explanation:
Time-sharing is a logical extension of multiprogramming where the CPU switches jobs rapidly (time slicing), allowing for interactive use.
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7In a Symmetric Multiprocessing (SMP) system:
A.One master processor controls slave processors
B.Each processor runs an identical copy of the OS and they communicate
C.Only one processor handles I/O
D.Processors are located in different geographical locations
Correct Answer: Each processor runs an identical copy of the OS and they communicate
Explanation:
In SMP, all processors are peers; no single processor is the master. They all run copies of the OS and share memory.
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8What defines a Distributed Operating System?
A.A collection of independent computers that appears to its users as a single coherent system
B.A system running on a single powerful mainframe
C.A system designed for real-time constraints
D.A system with multiple CPUs sharing the same clock and memory
Correct Answer: A collection of independent computers that appears to its users as a single coherent system
Explanation:
Distributed systems consist of loosely coupled processors (each with its own memory and clock) communicating via a network.
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9Which of the following is a strict requirement for a Hard Real-Time Operating System (RTOS)?
A.Virtual memory management
B.High throughput for batch jobs
C.Guaranteed completion of critical tasks within a specific time constraint
D.User-friendly interface
Correct Answer: Guaranteed completion of critical tasks within a specific time constraint
Explanation:
Hard RTOS systems (e.g., pacemaker, missile control) fail if a task is not completed by its deadline.
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10What are 'Tightly Coupled' systems also known as?
A.Parallel Systems
B.Batch Systems
C.Personal Computer Systems
D.Distributed Systems
Correct Answer: Parallel Systems
Explanation:
Parallel systems (Multiprocessors) share the same memory and clock, making them tightly coupled, as opposed to distributed systems which are loosely coupled.
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11Which component acts as the interface between a running program and the Operating System?
A.Bus
B.Interrupt Vector
C.System Calls
D.BIOS
Correct Answer: System Calls
Explanation:
System calls provide the Interface between a process (running program) and the operating system to request services.
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12In the context of OS structure, what is a Microkernel?
A.A structure where the entire OS runs in kernel mode
B.A kernel that is very small in file size
C.A structure that moves as much functionality as possible from the kernel into user space
D.A kernel designed only for microcomputers
Correct Answer: A structure that moves as much functionality as possible from the kernel into user space
Explanation:
Microkernels minimize the kernel by moving non-essential components (like file systems or device drivers) to user space, communicating via message passing.
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13What is the 'Bootstrap Program'?
A.The program that initializes the OS during computer startup
B.A program to manage boots
C.The first user program to run
D.The shutdown sequence
Correct Answer: The program that initializes the OS during computer startup
Explanation:
Stored in ROM or EEPROM, the bootstrap program initializes all aspects of the system and loads the operating system kernel into memory.
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14Which of the following is NOT a primary function of an Operating System?
A.File Management
B.Process Management
C.Source Code Compilation
D.Memory Management
Correct Answer: Source Code Compilation
Explanation:
Compiling source code is the function of a Compiler, not the Operating System. The OS manages resources like memory, processes, and files.
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15What is a Process?
A.A program in execution
B.A system call
C.A high-level language code
D.A program stored on the hard disk
Correct Answer: A program in execution
Explanation:
A program is a passive entity (file on disk), whereas a process is an active entity representing that program while it is running.
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16Which data structure does the OS use to store all information about a specific process?
A.Process Control Block (PCB)
B.Page Table
C.Interrupt Vector Table
D.File Control Block
Correct Answer: Process Control Block (PCB)
Explanation:
The PCB (also called Task Control Block) serves as the repository for any information that may vary from process to process (registers, state, ID, etc.).
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17Which of the following is NOT contained in a Process Control Block (PCB)?
A.Process State
B.Source code of the program
C.Program Counter
D.CPU Registers
Correct Answer: Source code of the program
Explanation:
The PCB contains execution data (state, registers, counters, memory limits) but does not contain the static source code.
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18When a process switches from the 'Running' state to the 'Ready' state, what is the likely cause?
A.Process termination
B.Waiting for user input
C.An interrupt occurs (e.g., time quantum expiry)
D.I/O completion
Correct Answer: An interrupt occurs (e.g., time quantum expiry)
Explanation:
A switch from Running to Ready usually happens when the scheduler stops the process to let another run (preemption) or a time slice expires.
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19What state is a process in when it is waiting for some event to occur (such as an I/O completion)?
A.Waiting (or Blocked)
B.Ready
C.New
D.Running
Correct Answer: Waiting (or Blocked)
Explanation:
A process enters the Waiting state when it cannot proceed until an external event, like an I/O operation, is finished.
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20The mechanism of saving the state of the old process and loading the saved state of the new process is called:
A.Process Creation
B.Swapping
C.Context Switch
D.Context Saving
Correct Answer: Context Switch
Explanation:
Context Switching is the process of storing the state of the current process so that it can be resumed later and restoring the state of the next process.
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21What is a significant downside of Context Switching?
A.It creates deadlocks
B.It decreases the number of processes
C.It is purely overhead; the system does no useful work while switching
D.It requires user intervention
Correct Answer: It is purely overhead; the system does no useful work while switching
Explanation:
Context switching takes CPU time to save and load registers/maps. During this transition, no user applications are executing.
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22Which system call is typically used in Unix/Linux systems to create a new process?
A.create()
B.start()
C.fork()
D.new()
Correct Answer: fork()
Explanation:
fork() is the standard system call in Unix-like operating systems to create a new process, which is a copy of the parent.
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23What is a 'Zombie' process?
A.A virus process
B.A process that has terminated, but its parent has not yet called wait()
C.A process running indefinitely
D.A process that consumes all CPU resources
Correct Answer: A process that has terminated, but its parent has not yet called wait()
Explanation:
A zombie is a process that has completed execution but still has an entry in the process table because the parent hasn't retrieved its exit status.
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24What happens to a child process if its parent terminates without invoking wait(), and the OS does not cascade termination?
A.It becomes a Zombie process
B.It is terminated immediately
C.It stops executing but remains in memory
D.It becomes an Orphan process
Correct Answer: It becomes an Orphan process
Explanation:
An orphan process is a child process whose parent has finished or terminated. In Unix, these are usually adopted by the init process.
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25Two processes are 'Cooperating' if:
A.One process can affect or be affected by the other process
B.They are both in the Ready queue
C.They have different Process IDs
D.They share the same CPU
Correct Answer: One process can affect or be affected by the other process
Explanation:
Cooperating processes share data or states. Independent processes do not affect one another.
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26Which of the following is NOT a reason for providing an environment for cooperating processes?
A.Hardware Protection
B.Information Sharing
C.Modularity
D.Computation Speedup
Correct Answer: Hardware Protection
Explanation:
Information sharing, speedup (via parallelism), and modularity are benefits of cooperating processes. Hardware protection is an OS function, not a reason for cooperation.
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27Which method allows processes to communicate by exchanging messages without sharing the same address space?
A.Virtual Memory
B.Shared Memory
C.Direct Memory Access
D.Message Passing
Correct Answer: Message Passing
Explanation:
Message passing (IPC) allows processes to communicate and synchronize actions via a message queue or channel, without accessing the same memory block.
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28In the Producer-Consumer problem using Shared Memory, what is the 'Producer' doing?
A.Consuming data from the buffer
B.Managing the memory allocation
C.Deleting the buffer
D.Generating data and placing it into the buffer
Correct Answer: Generating data and placing it into the buffer
Explanation:
The Producer process creates information/items and puts them into a shared buffer, while the Consumer retrieves them.
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29Which scheduler controls the degree of multiprogramming?
A.Long-term Scheduler
B.I/O Scheduler
C.Short-term Scheduler
D.Medium-term Scheduler
Correct Answer: Long-term Scheduler
Explanation:
The Long-term scheduler (Job scheduler) selects which processes are brought into the ready queue (memory), thus determining how many processes are in memory.
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30The Short-term Scheduler (CPU Scheduler) is responsible for:
A.Selecting which process should be executed next and allocating the CPU
B.Handling swap space
C.Creating the PCB
D.Moving processes from disk to memory
Correct Answer: Selecting which process should be executed next and allocating the CPU
Explanation:
The short-term scheduler selects from the processes that are ready to execute and allocates the CPU to one of them. It runs very frequently.
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31What action does the Medium-term Scheduler typically perform?
A.Swapping processes in and out of memory
B.Shutting down the system
C.Assigning PIDs
D.Creating new processes
Correct Answer: Swapping processes in and out of memory
Explanation:
The Medium-term scheduler removes processes from memory (swapping out) to reduce contention and reintroduces them later (swapping in).
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32In Direct Communication (Message Passing), how must processes be addressed?
A.Explicitly naming the recipient or sender
B.Broadcasting to all
C.Implicitly
D.Using a mailbox ID
Correct Answer: Explicitly naming the recipient or sender
Explanation:
In direct communication, send(P, message) sends a message to process P, requiring the explicit name of the process.
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33Which of the following refers to the number of processes completed per time unit?
A.Turnaround time
B.Waiting time
C.Response time
D.Throughput
Correct Answer: Throughput
Explanation:
Throughput is a measure of work done, specifically the number of processes that complete execution per time unit.
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34The 'exec()' system call is used to:
A.Wait for a child process
B.Exit the process
C.Replace the process's memory space with a new program
D.Create a new process
Correct Answer: Replace the process's memory space with a new program
Explanation:
exec() loads a new binary file into memory, destroying the old code image and replacing it with the new one, effectively running a new program within the same process.
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35Which type of operating system is typically used in embedded devices like washing machines or microwaves?
A.Network OS
B.Distributed OS
C.Batch OS
D.Real-Time OS (or Embedded OS)
Correct Answer: Real-Time OS (or Embedded OS)
Explanation:
Embedded devices usually require specific timing and resource constraints, often utilizing RTOS or specialized embedded OS versions.
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36What is the 'Kernel' of an Operating System?
A.The central core of the OS that manages resources and hardware
B.The shell that the user interacts with
C.The application software layer
D.The file system structure
Correct Answer: The central core of the OS that manages resources and hardware
Explanation:
The kernel is the one program running at all times on the computer; it manages input/output requests from software and translates them into data processing instructions for the CPU.
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37A process control block (PCB) is also known as:
A.I/O Control Block
B.Task Control Block
C.File Control Block
D.Memory Control Block
Correct Answer: Task Control Block
Explanation:
PCB and Task Control Block (TCB) are terms often used interchangeably to describe the data structure storing process information.
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38In Indirect Communication (Message Passing), messages are sent to and received from:
A.Registers
B.The Stack
C.Mailboxes (or Ports)
D.The Heap
Correct Answer: Mailboxes (or Ports)
Explanation:
In indirect communication, messages are not sent directly to a process but to a mailbox or port, which can be viewed as an object into which messages can be placed.
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39What constitutes the 'state' of a process?
A.Only the program code
B.The current activity of the process
C.The user who owns the process
D.The file name on the disk
Correct Answer: The current activity of the process
Explanation:
The state is defined by the current activity, such as New, Ready, Running, Waiting, or Terminated.
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40Which operation allows a parent process to synchronize its execution with the termination of a child process?
A.wait()
B.fork()
C.signal()
D.exit()
Correct Answer: wait()
Explanation:
The wait() system call suspends execution of the calling process until one of its children terminates.
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41What is a Clustered System?
A.A batch processing system
B.A single processor system
C.A mainframe
D.Two or more individual systems gathered together to perform computational tasks
Correct Answer: Two or more individual systems gathered together to perform computational tasks
Explanation:
Clustered systems gather multiple CPUs (usually individual systems) to work together, often sharing storage and linked via a LAN, to provide high availability.
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42During a Context Switch, where is the context of the old process saved?
A.In its Process Control Block (PCB)
B.In the CPU registers
C.In the secondary storage
D.In the new process's stack
Correct Answer: In its Process Control Block (PCB)
Explanation:
The OS saves the current state (registers, PC, etc.) into the PCB of the process being swapped out so it can be restored later.
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43Which command interpreter typically runs when a user logs in on a Unix system?
A.The Compiler
B.The Kernel
C.The Shell
D.The Loader
Correct Answer: The Shell
Explanation:
The Shell (e.g., Bash, sh) is the command interpreter that acts as the interface between the user and the operating system.
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44Which of the following is an example of a System Call used for File Management?
A.fork()
B.open()
C.wait()
D.time()
Correct Answer: open()
Explanation:
open() is a system call used to open a file. fork and wait are for process control, and time is for information maintenance.
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45In the evolution of Operating Systems, what replaced vacuum tubes?
A.Relays
B.Transistors
C.Integrated Circuits
D.Large Scale Integration
Correct Answer: Transistors
Explanation:
The second generation of computers (and OS evolution) moved from vacuum tubes to transistors, which were smaller, faster, and more reliable.
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46What does 'Program Counter' in the PCB indicate?
A.The total memory used
B.The number of programs running
C.The address of the next instruction to be executed
D.The time the process has been running
Correct Answer: The address of the next instruction to be executed
Explanation:
The Program Counter (PC) holds the memory address of the next instruction the process is scheduled to execute.
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47Synchronous Message Passing is also known as:
A.Rendezvous
B.Interrupt driven
C.Non-blocking
D.Polled
Correct Answer: Rendezvous
Explanation:
In synchronous message passing, the sender must wait for the receiver to accept the message (blocking send/receive), effectively synchronizing them at a 'rendezvous' point.
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48Which queue holds the processes that are residing in main memory and are ready and waiting to execute?
A.Job Queue
B.Ready Queue
C.Device Queue
D.Waiting Queue
Correct Answer: Ready Queue
Explanation:
The Ready Queue contains all processes that are in memory and ready to run, waiting only for the CPU to be assigned.
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49The transition from 'New' to 'Ready' state is approved by:
A.Short-term scheduler
B.Dispatcher
C.Long-term scheduler
D.User
Correct Answer: Long-term scheduler
Explanation:
The Long-term scheduler admits new processes into the system (memory), moving them from the 'New' state (creation) to the 'Ready' queue.
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50What is the primary advantage of Shared Memory over Message Passing for IPC?
A.No synchronization required
B.Works across networks
C.Easier to implement in distributed systems
D.Faster communication as it avoids system calls for data access
Correct Answer: Faster communication as it avoids system calls for data access
Explanation:
Once the shared memory region is established, accesses are treated as routine memory accesses, avoiding the kernel intervention required in message passing.