Operating Systems Basics Quiz

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Questions and Answers

What is meant by the degree of multiprogramming?

The number of tasks queued for execution.

The number of processes currently executing on the CPU.

The number of processes in memory simultaneously. (correct)

The number of CPU cores available.

Which of the following statements correctly describes multitasking?

It is only applicable to single-core processors.

It allows multiple programs to run completely at the same time.

It executes multiple processes by switching among them after a timeslice. (correct)

It creates a cloned instance of each program in memory.

What is the primary advantage of multiprogramming?

To allow a single process to monopolize CPU time.

To increase overall CPU utilization. (correct)

To decrease user interaction with processes.

To minimize the number of processes in memory.

How does a process differ from a program?

A process is a program in execution, whereas a program is a passive entity. Signup and view all the answers

What is the purpose of the Process Control Block (PCB)?

To store data needed to start or restart a process. Signup and view all the answers

Which of the following states indicates that a process has finished execution?

Terminated Signup and view all the answers

What indicates that the stack and heap sections of memory can change size during execution?

They can grow and shrink dynamically without overlapping. Signup and view all the answers

Which is true about the CPU scheduling goal?

To maximize CPU usage and quickly dispatch processes. Signup and view all the answers

Which section of process memory is primarily used for global variables?

Data section Signup and view all the answers

In which state does a process wait for an event to occur, such as I/O completion?

Waiting Signup and view all the answers

What is true about how many processes can run on a processor core at any given time?

Only one process can be executing on a core at a time. Signup and view all the answers

What does the CPU scheduler primarily select from?

Processes in the ready queue. Signup and view all the answers

What advantage do threads offer in a multicore system?

They can execute several CPU-intensive tasks in parallel. Signup and view all the answers

Which statement accurately reflects a characteristic of threads?

Each thread has its own Program Counter and stack. Signup and view all the answers

What is a primary disadvantage of threads sharing the same address space?

It can cause issues with thread synchronization. Signup and view all the answers

In which scenario would a thread likely be utilized?

When an application needs to perform multiple tasks simultaneously. Signup and view all the answers

What does it mean that threads are lightweight processes?

They have their own ID but share resources with other threads. Signup and view all the answers

What is the main responsibility of a dispatcher in process scheduling?

Switching the CPU core to another process Signup and view all the answers

Which of the following statements about context switch time is true?

Context switch time represents pure overhead with no useful work performed. Signup and view all the answers

In a tree of processes, which of these statements is correct?

Parent and children processes execute concurrently by default. Signup and view all the answers

Which of the following best describes process termination?

It results in the removal of the process from all queues. Signup and view all the answers

What must occur when a CPU switches to a new process?

The state of the old process must be saved. Signup and view all the answers

Which of the following is NOT a resource typically required by a child process?

Execution of parent processes Signup and view all the answers

What is a key factor that influences the length of context switch time?

Memory speed and number of registers to copy. Signup and view all the answers

Which process always has a PID of 1 in a Linux system?

The systemd process Signup and view all the answers

What is the consequence of a parent process terminating if certain operating systems do not allow child processes to exist independently?

No child processes can continue, leading to cascading termination. Signup and view all the answers

Which system call is used for a process to request its deletion when it completes its work normally?

exit() Signup and view all the answers

What scenario could lead to a process experiencing a fatal error?

The process attempts to access nonexistent memory. Signup and view all the answers

Which of the following best describes the nature of multithreaded applications?

Applications can execute more than one task simultaneously using multiple threads. Signup and view all the answers

What is the role of resource allocation in parent-child process relationships?

The parent may partition its resources or allow shared resources among children. Signup and view all the answers

In which situation would a process execute an error exit voluntarily?

The user provides a command that references a nonexistent file. Signup and view all the answers

What is a potential reason for a parent process to terminate one of its child processes?

The task assigned to the child is no longer needed. Signup and view all the answers

Which function in Win32 is equivalent to the UNIX kill system call for terminating a process?

TerminateProcess() Signup and view all the answers

Study Notes

Operating Systems Course Information

Course title: Operating Systems
Course code: 24CSC1031
Instructor: Wessam El-Behaidy
Main text reference: Operating System Concepts, Abraham Silberschatz, 10th Edition

Multiprogramming

Idea: The operating system keeps multiple processes in memory at once.
Degree of multiprogramming: The number of processes currently in memory.
System behavior: The OS switches between processes to improve CPU utilization and user satisfaction.
Key advantage: Increased CPU utilization.
Further advantage: Improved user satisfaction.

Multitasking/Timesharing

Description: A logical extension of multiprogramming.
CPU behavior: The CPU switches between multiple processes frequently using time slices.
Result: Provides users with a faster response time.

Process Concept

Definition: A program in execution.
Program state: Passive entity stored on a disk (executable file).
Process state: Active entity loaded to memory.
Program-Process conversion: Occurs when the executable file is loaded to memory.

Process Structure

Multiple processes per program: The same program may have several processes running.
Separate Resources: Processes have separate data sections.
Process environment: A process can be an environment for other code like a JVM

Process in Memory

Text section: Executable code.
Data section: Global variables.
Stack: Temporary data (function parameters, return addresses, local variables).
Heap: Memory dynamically allocated during runtime.
Fixed size: Text and data sections have fixed sizes.
Dynamic size: Stack and heap dynamically change size during runtime; they never overlap.

Process States

New: Process being created.
Ready: Waiting to be assigned to a processor.
Running: Instructions being executed.
Waiting: Waiting for an event to occur.
Terminated: Process has finished execution.
Important information: Only one process can run on a processor core at once. Multiple processes can exist in ready and waiting states.

Process Control Block (PCB)

Description: Data structure representing a process in the operating system.
Components: Process state, process number (PID), program counter, CPU registers, memory limits, scheduling information, scheduling queue pointers, list of open files.
Purpose: Serves as a repository for the data needed to start or restart a process.

Process Scheduling

Function: The CPU scheduler selects processes from the ready queue and allocates a CPU core to one of them.
Goals: Maximize CPU utilization and quickly switch between processes.
Queues:
Ready queue: Processes in memory, ready for execution.
Wait queue: Processes waiting for an event (e.g., input/output).

Context Switching

Description: Switching the CPU from one process to another.
Saving and loading process state: The old process's state needs to be saved and new process state loaded.
Dispatcher: The dispatcher is responsible for context-switching.
Overhead: Time spent doing context switching is overhead meaning it does not perform the tasks

Operations on Processes

Process creation: One process creates other processes.
Process termination: When a process finishes or needs to be killed.

Process Creation

Method: A process creates other processes, forming a process tree.
Parent and child process: A parent may have multiple children, but a child only one parent.
Concurrent execution: Parent and child processes often execute concurrently.
Waiting for child: Parent process may wait till the child completes.

Process Termination

Common reasons: Normal exit, error exit, fatal error, kill by an another process.
Cascating termination: When a process terminates, child processes also terminates.

Threads

Lightweight Processes: Threads share the same address space with other threads in the same process.
Sharing: Threads share code, data, heap sections, OS resources.
Multiple threads per process: A process can have multiple threads, enabling multiple tasks at once.

Examples of Multithreaded Applications

Photo thumbnails: Creating thumbnails for large collections of images (each image in a different thread, thus faster).
Web browser (One thread for browsing, another for retrieving data).
Word processor (One thread for displaying text, another for processing).

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Description

Test your knowledge on fundamental concepts of operating systems in this quiz. Questions cover topics such as multiprogramming, process management, CPU scheduling, and thread characteristics. Ideal for students studying computer science or preparing for exams.