Operating Systems Concepts Quiz

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the primary role of an operating system?

To manage computer hardware only

To perform calculations for user programs

To execute user programs exclusively

To serve as an intermediary between user and hardware (correct)

Which goal of an operating system focuses on improving user problem-solving?

Executing user programs efficiently

Making calculations faster

Providing security for applications

Simplifying the problem-solving process for users (correct)

Which statement accurately describes the abstraction provided by an operating system?

It allows direct hardware access for all applications.

It completely hides the hardware from the user.

It functions solely for resource management and nothing else.

It simplifies complex operations for application programs. (correct)

Which of the following is NOT a goal of an operating system?

Enhancing hardware performance Signup and view all the answers

What aspect does an operating system abstract for application programs?

The complexities of hardware functions Signup and view all the answers

What is the primary purpose of an interrupt in computing?

To allow hardware to communicate with the CPU. Signup and view all the answers

How do hardware devices typically send signals to the CPU?

Via the system bus. Signup and view all the answers

When can hardware triggers an interrupt?

At any time. Signup and view all the answers

What is classified as a system program?

A program that ships with the operating system but is not part of the kernel Signup and view all the answers

What component is primarily responsible for processing interrupts?

The CPU. Signup and view all the answers

Which of the following best describes middleware?

Software frameworks that provide additional services to application developers Signup and view all the answers

Which of the following describes an interrupt?

A temporary interruption of the CPU's current operation. Signup and view all the answers

What role does a device driver play in an operating system?

It facilitates communication between the operating system and the device controller Signup and view all the answers

In a computer system organization, how are CPUs and device controllers connected?

Via a common bus that provides access to shared memory Signup and view all the answers

Which statement accurately describes application programs?

They encompass all programs not associated with the operating system Signup and view all the answers

What is the primary purpose of the timer in process management?

To prevent infinite loops and resource hogging Signup and view all the answers

What occurs when the counter set by the operating system reaches zero?

An interrupt is generated Signup and view all the answers

What is a characteristic of privileged instructions in kernel mode?

They are exclusive to kernel mode and control critical operations Signup and view all the answers

What happens during a transition from user mode to kernel mode?

Certain privileged instructions can be executed Signup and view all the answers

What defines a process in the context of operating systems?

An instance of a program in execution Signup and view all the answers

Which of the following services is primarily responsible for file manipulation?

File management Signup and view all the answers

What type of service allows users to send messages and browse web pages?

Communications Signup and view all the answers

Which of the following best describes application programs?

They do not pertain to the system and are user-executed. Signup and view all the answers

What is the purpose of system services related to status information?

To provide detailed system performance and logging. Signup and view all the answers

Why are application programs considered operating system specific?

They depend on unique system calls and file formats of each OS. Signup and view all the answers

Which of the following is NOT a function of background services?

User interface display Signup and view all the answers

What is included in programming language support services?

Compilers and interpreters Signup and view all the answers

What distinguishes absolute loaders from overlay-loaders?

They load executable files into memory without modification. Signup and view all the answers

What is the primary function of process management in an operating system?

Creating and deleting both user and system processes Signup and view all the answers

In a single-threaded process, how many program counters are present?

One shared program counter Signup and view all the answers

What does effective memory management in an operating system primarily involve?

Deciding which processes and data to move in and out of memory Signup and view all the answers

Which layer of storage hierarchy requires explicit movement of data between levels?

Disk to memory Signup and view all the answers

What is the purpose of caching in an operating system?

To improve performance by temporarily storing data in faster storage Signup and view all the answers

What does spooling refer to in the I/O subsystem?

Overlapping output of one job with input of other jobs Signup and view all the answers

Which of the following best describes virtualization?

Executing multiple operating systems on a single hardware platform Signup and view all the answers

Which component is involved in managing cache data for efficient storage utilization?

Cache replacement policies Signup and view all the answers

In which situation is cache coherency critical?

In a multiprocessor environment accessing shared data Signup and view all the answers

What is one of the roles of the file-system management in an OS?

To organize files into directories and control access Signup and view all the answers

Study Notes

Introduction to Operating Systems

Saudi Electronic University offers an Operating Systems course.
The course is part of the College of Computing and Informatics.
The module includes Chapters 1 (Introduction) and 2 (Operating-System Services).

Course Content

Operating system functions
Computer system organization, architecture, and operations
Resource management
Virtualization
Computing environments
Operating-system services
User and operating-system interface
System calls and services

Learning Outcomes

Describe computer system organization and role.
Define computer system components, including multiprocessor systems.
Explain user and kernel mode transitions.
Identify operating system services and system calls.

What is an Operating System?

An operating system acts as an intermediary between a computer user and the hardware.
Its objectives include executing user programs and simplifying user problems.
It provides an abstraction layer for applications, making the hardware more user-friendly and efficient.

Computer System Structure

Users (people, machines, other computers) interact with application programs.
Application programs depend on the operating system.
The operating system manages the computer hardware.

Operating System Definition

No universally accepted definition of an operating system exists.
A good approximation is "everything a vendor ships when you order an operating system", but this description varies widely.
"The one program running at all times on the computer" is the kernel. However, other system programs and application software are part of the operating system, but not the kernel.

Computer System Organization

A computer system consists of one or more CPUs (central processing units).
These are connected via device controllers that provide shared memory access.
Each operating system has device drivers supporting each device controller facilitating communication.

I/O Operations Overview

I/O operations are requested by a program.
The device driver loads suitable registers within a device controller.
The controller determines the action (e.g., reading input).
Data is transferred from the device to a local buffer and to the controller.
The controller then notifies the operating system of completion, often through interrupts.
The driver then handles the result, potentially returning data or a completion status.

Interrupts

Hardware signals interrupts to the CPU via the system bus, frequently during I/O operations.
Interrupts are also critical for operating system and hardware interactions.
Each computer design has its own interrupt mechanism but with common core functions.
The OS saves CPU state during an interrupt.
The OS determines which interrupt occurred.
Separate segments of code handle different types of interrupts.

Computer System Operation

I/O devices and CPUs operate concurrently.
Each device controller has a local buffer.
Device controllers use drivers to handle communication, memory transfers, and I/O from devices.
A device controller informs the CPU of completion using interrupts.

Common Functions of Interrupts

Interrupts transfer control to an interrupt service routine usually through an interrupt vector.
The vector contains the addresses of various interrupt service routines.
Interrupt architecture saves the address of interrupted instruction, providing a return point.
A trap (or exception) is a software-generated interrupt cause by an error or a user request.
An operating system is interrupt-driven.

I/O Structure

The operating system returns control to the user program only upon I/O completion.
The CPU idles during I/O waiting.
At most one I/O request is outstanding at any time to avoid conflicts or contention.
The operating system returns to user programs without waiting for I/O completion through system calls.
I/O devices have status tables recording details like type, address, and status.
The operating system can reference these details to maintain information on I/O devices.

Computer Startup (Booting)

A bootstrap program loads at power-up or reboot (e.g. from ROM, EPROM) and is known as firmware.
The program initializes system aspects.
The bootstrap program loads the operating system kernel and initiates its execution.

Storage Structure

Main memory (RAM) directly accessible by CPU (volatile).
Secondary storage (non-volatile) offers large storage capacity.

Storage Structure (Cont.)

Hard Disk Drives (HDD) use magnetic platters.
Disk surfaces are logically segmented into tracks and sectors.
A disk controller manages interactions with the computer.
Increasingly popular non-volatile memory (NVM) devices (e.g., SSDs) offer speed improvements.

Storage Hierarchy

Storage systems are organized hierarchically based on speed and cost.
Information is frequently cached (copied) to faster storage (e.g., memory) for quicker access.
Device drivers manage I/O communication between controllers and kernel.
These drivers ensure consistent interface handling.

Storage-Device Hierarchy

The figure shows a hierarchy ranging from smaller, faster storage (registers, cache) to larger, slower storage (magnetic tapes).

How a Modern Computer Works

The CPU executes instructions from memory, managing various processes.
It manages I/O by way of the I/O controller and the device.

Direct Memory Access (DMA)

DMA allows high-speed I/O devices to communicate with memory without CPU intervention.
Only one interrupt is generated per block, rather than per byte transferred.

Operating-System Operations

The bootstrap program loads the OS kernel.
The kernel loads system daemons.
Hardware and software interrupts are handled by the kernel.
Software errors (e.g., division by zero) and other process problems are managed by the kernel.

Multiprogramming (Batch Systems)

Single-user systems cannot always keep the CPU and I/O devices busy.
Multiprogramming organizes multiple jobs, keeping the CPU occupied at all times.
A subset of jobs are kept in memory and scheduled (the CPU switches to a different job when necessary— for example, when waiting for I/O).

Multitasking extends batch systems, allowing users to interact with active jobs while running.
Response time, or time to a user input or output, is kept under a second.
The CPU frequently switches between jobs (often faster).
Processes are switched in or out of memory/storage (swapping).
Processes don’t need to be entirely loaded (virtual memory). Memory space is allocated for active jobs in RAM and other parts of the system.

Memory Layout for Multiprogrammed Systems

The layout shows how memory partitions can have the operating system as well as multiple user jobs allocated.

Dual-Mode Operation

Dual-mode operation (user mode, kernel mode) helps the OS protect itself and other system components.
Mode bit (hardware) defines user or kernel mode.
Only privileged instructions can execute in Kernel mode.
System calls change mode to kernel and return from call resets it to user mode.

Transition from User to Kernel Mode

A system call transition (invoking a system call from a program in user mode) into kernel mode is depicted.

Timer

A timer prevents infinite loops and resources being seized.
The timer generates interrupts after a specified period, allowing OS to regain control and to terminate programs when necessary.
Physical clock decrements a counter kept by the OS.
When it reaches zero, the OS is notified of need to regain control.

Process Management

A process is a program in execution.
Processes need resources (CPU, memory, I/O, files).
Process termination reclaims allocated resources.
Processes have a program counter, specifying the next instruction or next action to be taken.
Processes run sequentially.
Multi-threading has multiple program counters.
Many processes can run concurrently (multiplexed among CPUs).

Process Management Activities

The OS creates and deletes user and system processes.
The OS suspends and resumes processes.
The OS provides mechanisms for process synchronization.
The OS provides mechanisms for process communication and deadlock handling.

Memory Management

Executing a program requires loading its instructions and data into memory.
Memory management determines what is in memory at any given moment.
Memory management optimizes CPU utilization and response to users.
Memory management activities involve keeping track of which parts of memory are being used by whom.
The OS decides which processes, or portions of processes, and their data are to be moved into or out of memory.

File-System Management

The OS provides a uniform logical view of information storage.
The OS abstracts physical device properties to logical storage units (files).
Each storage medium has a controller device, such as a disk drive or tape drive.
Varying properties of each medium include speed, capacity and rate of data transfer. Access methodology can vary (sequential, random, etc).
Files often organized into directories (folders).
The OS may manage access control for each file.

Caching

Caching is a crucial principle that operates at various levels (e.g., hardware, OS, software) within a computer system.
It involves temporarily copying data from slower to faster storage for faster access.
The cache is checked first; if data is found, it is retrieved from the faster storage (cache).
Cache management is important for system design and involves considerations of cache size and replacement policies.

Characteristics of Storage Types

A table showing typical size, technology, access time and bandwidth of different levels of computer storage (from registers, to cache to memory and to permanent storage like disks.

Migration of Data "A" from Disk to Register

Multitasking environments should care about using the most recent values from storage regardless of hierarchy location.
For multiprocessor environments, all CPUs need consistent data values stored in cache; appropriate coherency techniques are implemented in hardware.
Distributed environments are more complex, with several copies of data potentially extant.

I/O Subsystem

The I/O system hides hardware peculiarities from the user.
The OS manages I/O, through buffering, caching, and spooling, to efficiently and manage data transfer and utilization.
Device drivers manage storage devices (e.g., disk, tapes).
The general driver interfaces is available to developers.

Virtualization

Use cases for virtualization range from exploring compatibility between OSes to quality-assurance testing.
Laptops and desktops can run different OSes for compatibility testing or to develop and execute apps.
Virtualization allows OSes to run in a virtual machine.
This facilitates compatibility and efficient use of resources.

Virtualization (Cont.)

Virtualization (e.g., using software like VMware ESX) allows running multiple OSes on a single physical system.
If the host CPU differs from the guest OS, the emulated approach using interpretation (instead of native code) is the mechanism used.

Computing Environments- Virtualization

A visual diagram illustrating different levels of computing environments with virtual machines.
The different levels shows relationships between processes running, programming interfaces, system kernel, virtual machines, and the underlying compute platform (hardware).

Computer-System Architecture

Most systems use a general-purpose processor, supplemented by other specialized processors.
Multiprocessor (parallel) systems are increasingly common, offering increased performance, throughput, and reliability (graceful degradation)

Symmetric Multiprocessing Architecture

A graphic illustrating how processors work together to support multiprocessing (shared memory access across the different CPUs)

Dual-Core Design

A diagram illustrating how dual-core computer processing units, or CPUs, work together.

Computing Environments

A list of computing environments that are related to operation systems.

Traditional

Stand-alone general-purpose machines are becoming more common in systems sharing data via network (e.g. through internet).
Stand-alone machines are becoming networked/interconnected.

Client-Server Computing

Systems supplanted dumb terminals by smart PCs.
Many systems operate as servers to manage requests generated by client programs.
File-server systems provide storage, retrieval of data (files).
Compute-server systems support client requests for services (e.g., databases).

Cloud Computing

Cloud computing extends across networks, delivering computing, storage, and applications as services.
Concepts of virtualization and networked operations are core to cloud computing.
Many different types of cloud computing models support the logical extension of virtualization (e.g, Amazon EC2).
Cloud services are often categorized by: deployment method, service level, etc.).

Cloud Computing (Cont.)

Cloud environments usually include many traditional OSes supplemented by VM managers and cloud management tools.
Internet connectivity necessitates security measures such as firewalls and load balancers. Load balancing ensures a greater efficiency in handling traffic to the cloud platform.

Free and Open-Source Operating Systems

GNU/Linux and BSD UNIX (Mac OS X core) are prominent examples.
These are often preferred because of the source-code availability and absence of licensing fees.

Operating System Services

The OS provides an environment and set of functions (user interface, program execution, I/O operations, file-system manipulation, communications, error detection, and others) for programs and users.

Operating System Services (Cont.)

A detailed and comprehensive set of OS system functions and services are provided.