Operating System Role and Services

23CSE2010 - Operating System

• Course has 3 credits
• It's a S.Y. (SEM-IV) class
• CA Marks are 50
• End Semester Marks are 50
• Academic year is 2024-2025 and Semester-IV

Unit-I INTRODUCTION TO OPERATING SYSTEMS

• Topics include the evolution of operating systems, OS definitions and overviews
• Also covers objectives, functions, and types of operating systems such as Batch, Multi-programming, Timesharing, and Real-time OS
• Functions, OS Structure (Monolithic, Microkernel, Layered, Client-Server), OS services (system calls, interrupt handling)
• System Programs, Kernel and user space, OS Generation, and System Boot are also covered
• Process definition, the process concept from system programmer's and OS views, including process states and Process Control Block (PCB)
• Process Creation and Termination (fork, exec, process hierarchy, exit, wait), Context switching
• Types of schedulers (long-term, short-term, medium-term), Scheduling algorithms- Preemptive vs. Non-Preemptive Scheduling (FCFS, SJF, RR, Priority Scheduling)

Unit-II PROCESS & THREAD MANAGEMENT

• Process definition, the process concept from system programmer's view of processes – operating system's views of processes, States,
• Process Control Block (PCB), Process Creation and Termination (fork, exec, process hierarchy, exit, wait), Context switching
• Types of schedulers (long-term, short-term, medium-term), Scheduling algorithms- Preemptive vs. Non-Preemptive Scheduling (FCFS, SJF, RR, Priority Scheduling
• Multilevel Queue Scheduling, Multi-Level Feedback Queue (MLFQ), Completely Fair Scheduler (CFS), Lottery Scheduling)
• Thread Management: Threads Concepts, Thread Models, Multithreading Models, Thread Issues, Thread Scheduling.

Unit-III PROCESS SYNCHRONIZATION AND DEADLOCKS

• Cooperating processes and Race Conditions
• The critical-section problem, Peterson's solution
• Semaphores
• Classic problems of synchronization, including Producer-Consumer, Dining-Philosophers, Readers and Writers, and Sleeping Barber problems
• Inter-process Communication (IPC) Overview, IPC System Examples, Communication in Client-Server Systems

Deadlock

• System Model
• Deadlock characterization
• Deadlock and Starvation
• Methods for Handling Deadlocks
• Resource Allocation Graphs
• Deadlock Prevention/Avoidance/Detection/Recovery

Unit-IV MEMORY & STORAGE MANAGEMENT

• Memory Management: Logical vs. physical address space, Contiguous Memory Allocation, Allocation Methods
• Fragmentation and Compaction
• Cache Memory
• Paging, Demand paging, Segmentation
• Virtual memory in modern OS
• Page Replacement Algorithms like FIFO, LRU, Second Chance, and OPT
• Thrashing and avoidance techniques

Storage Management

• File-System Structure
• Access Methods
• Disk Structure and Scheduling
• Free-Space and Swap space management

Unit-V Advance Operating System

• Distributed Operating Systems: System Architectures
• RTOS & Scheduling (Rate-monotonic scheduling, Earliest Deadline First)
• Virtualization and Operating-System Components
• Linux System: Design Principles, Process Management, and Scheduling
• Mobile OS - Android

What is an Operating System?

• OS components consist of a User Interface, Software Management component, and Hardware Management component
• The User Interface provides a platform for user interaction with hardware
• Software Management oversees software operations and interactions
• Hardware Management controls and allocates hardware resources

Characteristics of an Effective Operating System

• Resource Management: Coordinates and manages devices and files
• Scheduling: Prioritizes and manages task execution
• Security: Protects data and resources from unauthorized access
• Memory Management: Efficiently allocates and deallocates memory resources.
• Software Interaction: Seamless communication with various software applications

Evolution of Operating System

Includes the following generations:

• First Generation Computers (1940-1950)
• Second Generation Computers (1950-1960)
• Third Generation Computers (1960-1970)
• Fourth Generation Computers (1980- )
• Fifth Generation Computers (2000- )

First Generation Computers (1940-1950)

• Used vacuum tubes for circuitry; magnetic drums for memory
• Computers were huge, filling entire rooms
• Relied on machine language
• Operating systems didn't exist
• Used serial processing
• Devices like UNIVAC and ENIAC are examples

Advantage of First Generation Computers

• Was only electronic device

Disadvantage of First Generation Computers

• Large Size
• Vacuum tubes burn frequently
• Produce heat and high malfunctions

Second Generation Computers (1950-1960)

• Transistors replaced vacuum tubes
• Batch systems were used, creating a base for multitasking
• High-level programming languages (COBOL, FORTRAN) developed
• Batch processing submitted jobs in batches, loaded sequentially by an operator
• Job Control Language (JCL) introduced to manage jobs
• Programs executed without user interaction
• IBM 701 and IBM 7090 are examples of 2nd gen computers

Advantage of Second Generation Computers

• Much smaller in size
• Faster than the previous geneneration of computers

Disadvantage of Second Generation Computers

• Overheated and had maintanence problems

Third Generation Computers (1960-1970)

• Multiprogramming allowed multiple programs to run simultaneously, improving CPU utilization
• Time-sharing allowed multiple users to share computing resources interactively
• Operating systems like UNIX and OS/360 emerged
• Included file systems, device drivers, memory management

Fourth Generation Computers (1980-)

• Graphical User Interfaces (GUI's) made systems more user-friendly (e.g., Windows and macOS)
• Distributed systems introduced to connect multiple computers for resource sharing
• Networking capabilities supported communication over LAN

Fifth Generation Computers (2000-)

• Mobile and Embedded Systems: Operating systems optimized for mobile devices and IoT (e.g., Android, iOS)
• Virtualization and Cloud Computing: Virtual machines and cloud-based services became widespread
• Focus on data security and scalable architectures

Evolution Summary:

• 1st Gen: No OS, manual programming (ENIAC, UNIVAC)
• 2nd Gen: Batch systems, JCL (IBM 701, IBM 7090)
• 3rd Gen: Multiprogramming, time-sharing (UNIX, OS/360)
• 4th Gen: GUI, personal computing, networking (Windows 95, macOS)
• 5th Gen: Mobile systems, virtualization, cloud (Linux, Android, iOS)

Overview of Operating Systems

• Consists of Hardware, OS, System Software, and Applications
• Users interact with this software

Dividing the System

Consists of four components:

• Hardware: provides basic computing resources like CPU, memory, and I/O devices
• Operating System: controls and coordinates the use of hardware among applications and users, assigns jobs to hardware
• Application Programs: Defines system resource use to solve user problems and are ready-made packages
• Users: people, machines, and other computers

Advantages of Operating Systems

• Source of Computing
• Provides User-Friendly Interface
• Resource Sharing
• Involves No Coding Lines
• Data Protection
• Multitasking

Drawbacks of Operating Systems

• Frequent Updates
• Costs
• Learning Curve
• Resource Usage
• Security Vulnerabilities
• Dependancies
• Compatibility Issues

Services of OS

Includes:

• Process Management: Encompasses process scheduling and resource allocation
• Memory Management: Involves memory optimization and protection
• Resource Management: Manages memory allocation and CPU time distribution
• Security: Implements access controls and encryption
• Job Accounting: Includes time and resource tracking and monitoring
• Backup and Recovery: Data backup/recovery
• Virtualization: Multiple OS and Application Management
• Device Management: Managing printers and keyboards
• File Management; Creation/deletion of files

Functions for OS

• File management organizes the file system, including creation, deletion, and manipulation of files and directories
• Device management handles input/output devices, providing necessary drivers and interfaces for communication
• Networking establishes and manages network connections, handling protocols and sharing resources
• User interface enables user interaction, with GUI or CLI options
• Backup and recovery provides mechanisms for data backup and recovery after failures
• Virtualization allows multiple OS/applications to run on a single physical machine

Operating System Goals

• Robustness: Maintains performance under stress
• Convenience: Ensures user-friendliness and ease of use
• Scalability: Supports growth and increased demand
• Efficiency: Optimizes resource use and performance
• Reliability: Guarantees consistent and error-free operation
• Portability: Allows software to run on different systems

Types of Operating Systems

• Batch Operating System - Sequencing
• Multiprogramming Operating System - No ideal Time for CPU
• Time-sharing Operating System - Multitasting
• Distributed Operating System - Coordination
• Network Operating System - Connectivity
• Real-time Operating System - Timeliness
• Multiprocessing Operating System - Parallelism
• Embedded Operating Systems - Specialization

Batch System details

• System allows multiple users to use it, without direct communication among them
• Keeps users separate in "batches"
• Suited for functions needing separate parts of a common project
• Examples include payroll and bank statements
• Multiple users can share the batch systems, so that idle time of the batch is very low
• Large work may be managed repeatedly

Disadvantages of Batch Systems

• Operators should be familiar with batch systems
• Systems hard to debug
• Jobs wait if one fails
• Turnaround time can be high
• One failing job has knock-on effects

Multiprogramming Operating Systems

• Advanced version of batch, keeps CPU busy with multiple programs
• Each program needs execution ("CPU") time and input/output (I/O) time
• When one program waits for I/O, CPU switches to another
• Improves overall efficiency of system
• Windows, Linux, MacOS are examples

Advantages of Multiprogramming

• There is always a program to run
• Response time is faster
• Resources like I/O are better because multiple programs running better manage them
• The processor keeps working by switching to other tasks when one program waits for I/O
• Can handle both short and long tasks

Disadvantages of Multiprogramming

• No direct interaction between users/computer
• Complexity of managing all programs
• More memory needed to run programs
• Switching programs adds overhead, which can slow performance
• Deadlocks may occur

Time-sharing OS

• Each task given time to execute, to ensure everything works smoothly
• These Systems known as multitasking
• The time that each task gets to execute is called quantum.
• After this time interval is over OS switches over to the next task

Time Sharing Advantages

- Each task gets an equal opportunity.
- CPU idle time can be reduced.
- Resource Sharing between multiple users.
- Time-sharing allows users to work concurrently. Its reduce waiting time.

Time Sharing Disadvantages

- It has difficulty with consistency.
- A security and integrity problem with user programs and data.
- High Overhead because need for scheduling, context switching.

Distributed Operating Systems

• A collection of independent computers to achieve common goal by sharing resources, data, tasks by over the network
• The autonomous computers will communicate among each system by sharing resources and files
• Client-Server / Peer-to-Peer Systems

Key characteristics of Centrilized Systems

• Single point of Control, Scalability Issues, Failure, No Fault Tolerance, No Coordination and Communication, No Resource Sharing
• Performance degrades with increased loading
• Divided into layers, with Layer 0 being Hardware
• Functionality is separated into different layers
• Easy to implement and designed

Distributed OS Advantage

- Failure of one will affect the others
- Less load of host computer
- Computation that ensures since resources are being shared

Distributed OS Disadvantage

- Network shutdown halts communication
-  Language used in establishing distributed networks not well-defined
-  Systems are not reaily available and very expensive

Multiprocessing Operating System

• Memory Utilization
• Resource Sharing

Network Operating System

- Centralized management
- Resource sharing
- Scaleability, Security
- Remote Access

Disadvantages of Networking Operating Systems

- Complexity, Cost, Security Compatibility, Maintenaince

Embedded Operating Systems

- A combination of software and hardware
- Requires a real-time operation, to perform specific operations, with the advantage of a reactive operation

Advantages of Embedded Operating Systems

- Lower Costs, Small Sizes, and Effectiveness to due small power and being portable

Disadvatnages of Embedded Operating Systems

- Limited resources, limited flexibility with adaptabiltiy. Programming is difficult.
- Lack of Standardization and hardware depence

Real Time Operating System

• (RTOS) is design of responding to large number of events with the ability of multitasking and deadline management - Includes industrial control, telephone switching, flight control etc

Key Characteristics of RTOS

• Determinist Behavior, Stable and consistent with the multi-tasks through the use of prevention of data loss and prevention of data loss

Computer System Structure includes

• Simple structure, monolothic structure (the kernel), layered structure and microkernel structure

Simple Structure

• Used at the very beginning as it is an old Structurre and not well designed with an ex-MS-DOS • At Bottom BIOS DD, i.e. HW with a DD access for the hw • At the Top, there’s applicatiion Pragram Residencial System Program access while the hw interface and levels of functionality are not separate

Advantage of Simple Structure

• Simplity to develop with better application

Disadvantage

- Less secure and not abstract with no designed structutre.

Monolothic Structure

- Followed by Unix OS, the Ist User with the compiler interpretter
- 3rd System call at interface with the hw and the functionallitiies
- 5th Monolohitic structure

• This operating system works in the kernel space in the monolithic system • The monolithic kernel is quite fast as the services such as memory management, file management, process scheduling etc • A set of primitives or system calls implement all operating system services such as process management, concurrency, and memory management with Linux, BSDs, Solaris, DOS, OpenVMS

Monolothic Advantage

• Fast execution from accessing functions, while being quick massibly. Not to mention easy implementations

Monohtic disadvantages.

if the component system fails then the entire system crashes. which are complex, dificult to do.

The Kernal in Operating Systems

- Helps ensure everything works together smoothly and efficiently, and is the bridge between Software and Hardware
- Applications with processes to handle tasks like printers, keyboards, managing hardware functions and facilitating communications

Layered Structure

• Divide into nor of Layers to create user friendly • Hardware is Broken down, implemented desgn, and ex widows •Layered Structure is a type of system structure in which the different services of the operating system are split into various layers. Where each layer has a specific well-defined task to perform. It was created to improve the preexisting •structure like the Monolithic structure ( UNIX ) and the Simple structure (MS-DOS ) with EXampkes like Windows NT operating

Adventages and Disadvatnages

• Easy Modularity; the debugging updaing is high. and well easy to deisgn and defined is more complex and comes off as slower in execution

User modes of Kernal

• When the computer system executes on behalf of a user application, the syster in user modeswitches to kernel mode •At system boot time, the hardware starts in kernel mode user modewhen interefered •The system always switches, which can cause •In Monolithic OS and Small strutrure with less coding

Micokernal

• Main function to allow for client server messages and passaging to a user

kernal adbantages and diadvatnages

• Allows to operate to be Portable between platforms, smaller, with each part successfuly • easy to add and be kept •It may be cost and not effeciently structured with the chance that if kerna fail, it will crash everything

OS services by user and Interup handling.

A system call is a way for a user program to interface with the operating system. The program requests several services, and the OS responds by invoking a series of system calls to satisfy the. A system call can be written in assembly language or a high-level language like C or Pascal. System calls are predefined functions that the operating system may directly invoke if a high-level language is used.

Process Types

• Proccess control, flile management, deice and information with communications

  • An interrupt is a signal emitted by hardware or software when a process or an event needs immediate attention. • hardware or software when a process or an event needs immediate attention

Hardware System Types

• Maskable and  Non-Maskable Interrupts to get user system
• system calls with the operation of Divide be Zero
• Interrupt in OS with communication
• Interrupt in OS with user request for the type of memory

The Boot and Functionallity

• The booting process loads the OS from storage into RAM, enabling the computer to operate

• What is Power-On Self-Test (POST) Booting?
• is the initial diagnostic process performed during a computer, with functional components. If issues to arise, it will load OS and boot from there.

Explore the essential role of operating systems in device management and data preservation. Understand how OS services support file organization and user interaction. Learn about the crucial services that enable file sharing across devices and more.