Introduction to Operating Systems

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Questions and Answers

What role does an operating system play between a user and computer hardware?

It enables direct access to hardware components.

It serves as an intermediary between the user and hardware. (correct)

It acts as a firewall to protect hardware.

It overrides user commands to optimize performance.

Which of the following is a goal of an operating system?

To execute user programs and alleviate user problems. (correct)

To replace hardware components for better performance.

To ensure security of user data exclusively.

To facilitate direct interactions between applications and hardware.

Which component of the computer system provides the basic computing resources?

Application programs

Hardware (correct)

Operating system

Users

What is the kernel in an operating system?

The active component of an OS that runs at all times. Signup and view all the answers

What is the primary function of the shell in an operating system?

To interact with application programs and execute commands. Signup and view all the answers

From the user's perspective, what is a primary design goal of an operating system?

To make resource monopolization easy for a single user. Signup and view all the answers

Which of the following best describes process management in operating systems?

It oversees the execution of programs while handling user inputs. Signup and view all the answers

What does the resource allocator in an operating system do?

Manages and assigns system resources to various programs. Signup and view all the answers

Which scenario allows a parent process to terminate a child process?

Parent is exiting. Signup and view all the answers

What does dispatch latency measure?

The time it takes to change from one process to another. Signup and view all the answers

Which of the following is a disadvantage of First-Come, First-Served (FCFS) scheduling?

One process can monopolize the CPU, leading to long waiting times. Signup and view all the answers

What is the key principle of Shortest-Job-First (SJF) scheduling?

It allocates the CPU to the process with the smallest next CPU burst time. Signup and view all the answers

Which scheduling criterion measures the time a process takes from submission to receiving the first response?

Response time Signup and view all the answers

Which of the following scheduling algorithms is designed to minimize average waiting time?

Shortest Job First Signup and view all the answers

What characterizes Shortest Remaining Time (SRT) scheduling?

It can preempt currently running processes if a shorter burst arrives. Signup and view all the answers

In the context of CPU scheduling, what does throughput represent?

The total number of processes that complete in a given time frame. Signup and view all the answers

What is a key difference between a program and a process?

A program is a static object while a process is a dynamic object. Signup and view all the answers

Which state indicates that a process is ready to run but waiting for CPU availability?

Ready State Signup and view all the answers

What does the program counter do?

It indicates the address of the next instruction to be executed. Signup and view all the answers

Which of the following best describes fragmentation in the heap?

Wasting of memory space leading to inefficiencies. Signup and view all the answers

Which one of the following is not included in a process?

Method libraries Signup and view all the answers

In which state is a process created?

New State Signup and view all the answers

Which of the following best characterizes a process?

It is an active entity that must progress sequentially. Signup and view all the answers

What happens when a process is in a blocked state?

It is waiting for some event like I/O completion. Signup and view all the answers

What is the primary aim of the approach that executes the process with the least remaining time first?

Minimize average waiting time Signup and view all the answers

In a preemptive priority scheduling system, what can happen to lower-priority processes?

They may experience indefinite blocking Signup and view all the answers

What is a crucial factor in the performance of Round-Robin scheduling?

The size of the time quantum Signup and view all the answers

What characterizes CPU-bound processes compared to I/O-bound processes?

Longer CPU bursts and shorter I/O bursts Signup and view all the answers

What does the ready queue contain?

Processes that are ready and waiting to execute Signup and view all the answers

Which of the following statements is true regarding CPU burst distribution?

It helps in understanding process completion Signup and view all the answers

Which of the following is a function of an Operating System?

Provide a user interface Signup and view all the answers

Which scheduling algorithm is specifically designed for time-sharing systems?

Round-Robin Scheduling Signup and view all the answers

What does the term 'multiprogramming' refer to in an OS?

Executing multiple processes simultaneously. Signup and view all the answers

Which process scheduling queue is responsible for handling processes that need to wait for a specific I/O device?

Device Queue Signup and view all the answers

What is the primary function of the Memory Management Unit (MMU)?

To translate logical addresses into physical addresses. Signup and view all the answers

Which of the following best describes the term 'thrashing' in an Operating System?

A situation where excessive paging occurs, causing high disk activity. Signup and view all the answers

Which type of process is created and executed by the system to perform specific tasks like printing or data transfer?

System process Signup and view all the answers

In the context of process scheduling, what does the term 'starvation' refer to?

A process that never gets CPU time due to scheduling policies. Signup and view all the answers

Which OS concept involves creating a virtual CPU for each process?

Time-sharing Signup and view all the answers

What is the primary function of the I/O buffer in an Operating System?

To hold data temporarily while it is being transferred. Signup and view all the answers

Study Notes

What is an Operating System?

An operating system is a program that functions as an intermediary between a user and the computer hardware.
It acts as a collection of system programs responsible for managing and coordinating all the operations of a computer system.
Examples of operating systems include UNIX, Mach, MS-DOS, MS-Windows, Windows/NT, Chicago, OS/2, MacOS, VMS, MVS, and VM.

Operating System Goals

Facilitate user program execution and make solving problems easier.
Provide a convenient and user-friendly interface.
Ensure efficient use of computer hardware resources.

Computer System Components

Hardware: Provides the fundamental computational resources (e.g., CPU, memory, I/O devices).
Operating System: Controls and coordinates the utilization of hardware among various applications and users.
Application Programs: Define the specific ways resources are used to solve user computing problems (e.g., compilers, databases, video games, business software).
Users: Individuals, machines, or other computers.

Operating System Definitions

Resource Allocator: Manages and allocates the system's resources.
Control Program: Controls the execution of user programs and manages I/O device operations.
Kernel: The core program that continuously runs, with all other programs considered applications.

OS Components

Kernel: The active part of the OS, constantly executing, and responsible for interacting with hardware. (Examples: device drivers, DLL files, system files).
Shell: Acts as a command interpreter, interacting with application programs. It executes instructions given to the OS, referred to as commands.

User and System Views of an OS

User View: The OS is designed for a single user to monopolize its resources, maximizing the user's workflow and providing ease of use.
System View: The OS is viewed as a control program managing user program execution, preventing errors and ensuring proper computer usage. Its primary focus is on I/O device operation and control.

Functions of an Operating System

Process Management:
- A process is a program in execution.
- The heap is used to allocate memory blocks of varying sizes during program execution.
- Fragmentation can occur in the heap as memory space is wasted, leading to inefficiencies.

Process Concept

A process encompasses more than just the program code itself (known as the text section).
It includes the current activity, represented by the program counter's value and the contents of the processor's registers.
It also includes the process stack (for temporary data like method parameters, return addresses, and local variables) and a data section containing global variables.
An operating system executes various types of programs:
- Batch system: Jobs
- Time-shared systems: User programs or tasks
A process, a program in execution, must proceed in a sequential manner.

Process Components

Program Counter: Indicates the address of the next instruction to be executed for that process.
CPU Registers: Varies based on computer architecture but contain relevant data for process execution.

Process State

New State: The process is being created.
Running State: The process is currently being executed by the CPU.
Blocked (or Waiting) State: The process is waiting for an event to occur, like I/O completion.
Ready State: The process is prepared to run and is waiting for CPU availability.
Terminated State: The process execution has completed.

Process and Program: The Difference

Program and process are essentially the same, but a process is a program in execution.
Program is static, while process is dynamic.
Program resides in secondary storage, while process is in main memory.
Program has unlimited lifespan, while process has limited duration.
Process is an 'active' entity, while program is 'passive'.
Program uses programming language, while process uses assembly language or machine language.

Parent-Child Process Termination

Parents can terminate child processes (abort).
Reasons include:
- Child exceeding allocated resources.
- Task of child no longer required.
- Parent exiting.
The OS prevents children from running if their parent terminates.
Cascading termination can occur.

Dispatcher

The module that hands control of the CPU to the process chosen by the short-term scheduler.
It involves context switching, transitioning to user mode, and jumping to the appropriate location in the user program to resume execution.

Dispatch Latency

The time required for the dispatcher to stop one process and start another.

Scheduling Criteria

CPU Utilization: Aiming to keep the CPU as busy as possible.
Throughput: Number of processes completing execution per unit of time.
Turnaround Time: Amount of time required to execute a process completely.
Waiting Time: Amount of time a process spends waiting in the ready queue.
Response Time: Time from request submission until the first response is generated (not necessarily output), relevant for time-sharing systems.

First-Come, First-Served Scheduling (FCFS)

The simplest CPU scheduling algorithm, allocating the CPU to the process that requests it first using a FIFO queue.
Easy to implement, but can result in long average waiting times, especially in time-sharing environments where one process might monopolize the CPU.

Shortest-Job-First Scheduling (SJF)

Assigns the CPU to the process with the shortest next CPU burst time.
Can be preemptive or non-preemptive.
Preemptive SJF allows a process with a shorter burst to interrupt the currently running one.
Optimal for minimizing average waiting time, but challenging due to the need to predict next CPU burst lengths accurately.

Shortest Remaining Time (SRT)

A preemptive version of SJF.
If a new process arrives with a shorter remaining CPU burst time than the executing process, the CPU switches to the new process.
Aims to minimize average waiting time by always executing the process with the least remaining time.

Priority Scheduling

Assigns the CPU based on process priority levels, with higher priority processes running before lower priority ones.
Can be preemptive (interrupts running processes for higher priority ones) or non-preemptive.
Potential for indefinite blocking or starvation of low-priority processes is a concern.

Round-Robin Scheduling (RR)

Primarily for time-sharing systems.
Each process receives a fixed time slice or 'quantum' for execution.
The ready queue is treated as a circular queue, and the CPU scheduler allocates the CPU for up to one quantum at a time, preventing any process from monopolizing the CPU.
Performance depends heavily on the time quantum size.

CPU Burst

The time a process spends executing on the CPU before completion or requiring I/O operations.
Processes alternate between CPU bursts and I/O bursts.
CPU-bound processes have longer bursts, while I/O-bound processes have shorter bursts.
Understanding burst distribution is crucial for effective CPU scheduling and optimizing system performance.

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Description

This quiz explores the fundamental concepts of operating systems, including their functions and goals. It covers the interaction between users and hardware, the components of computer systems, and examples of various operating systems. Test your understanding of how operating systems manage resources and facilitate user applications.