Operating Systems: Fundamentals and Types, Slides of Operating Systems

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Chapter 1: Introduction

Chapter 1: Introduction

► Roadmap:-------

► What Operating Systems Do? ► Operating-System Structure ► Operating-System Operations ► Process Management ► Memory Management ► Storage Management ► Protection and Security ► Types of Operating system ► Window vs Linux

What is an Operating System?

◈ A program that acts as an intermediary between a user of a

computer and the computer hardware

◈ Operating system goals:

Execute user programs and make solving user problems easier Make the computer system convenient to use Use the computer hardware in an efficient manner

What is an Operating System?

◈ An operating system (OS) is the interface between user

and computer hardware.

◈ It manages the hardware attached to the computer system.

◈ An operating system is a system software.

◈ Operating system perform various task regarding

computer system like memory management, controlling

peripheral devices such as disk drives and printers,

handling input and output, file management etc.

Computer System Structure

◈ Computer system can be divided into four components:

Hardware – provides basic computing resources ◈ CPU, memory, I/O devices Operating system ◈ Controls and coordinates use of hardware among various applications and users Application programs – define the ways in which the system resources are used to solve the computing problems of the users ◈ Word processors, compilers, web browsers, database systems, video games Users ◈ People, machines, other computers

Operating System Definition

◈ OS is a resource allocator

Manages all resources

Decides between conflicting requests for efficient and fair resource use

◈ OS is a control program

Controls execution of programs to prevent errors and improper use of the computer

4.Device Management This function of operating system is used to manage different devices that are connected with the computer system. An operating system interact with hardware device through specified device drivers.

5.File Management An operating system manages the files and directories of computer system. A file can be defined as a collection of information or data that is store in the memory of computer system. An operating system allow us to create, delete, save, edit files in a computer system.

Basic functions of operating systems

Process Management

► A process is a program in execution. It is a unit of work within the system. Program is apassive entity , process is anactive entity.

► Process needs resources to accomplish its task ► CPU, memory, I/O, files ► Initialization data

► Single-threaded process has one program counter specifying location of next instruction to execute ► Process executes instructions sequentially, one at a time, until completion

► Multi-threaded process has one program counter per thread

► Typically system has many processes, some user, some operating system running concurrently on one or more CPUs ► Concurrency by multiplexing the CPUs among the processes / threads

• A file is a collection of related information defined by its creator.
• Commonly , files represent programs (both source and object forms) and data.

► Files usually organized into directories ► Access control on most systems to determine who can access what ► OS activities include

► Creating and deleting files and directories

► Primitives to manipulate files and directories

► Mapping files onto secondary storage

► Backup files onto stable (non-volatile) storage media

File-System management

I/O Subsystem

◈ One purpose of OS is to hide peculiarities of hardware devices from the user

◈ I/O subsystem responsible for

Memory management of I/O including buffering (storing data temporarily while it is being transferred), caching (storing parts of data in faster storage for performance), spooling (the overlapping of output of one job with input of other jobs) General device-driver interface Drivers for specific hardware devices

- A device driver performs the following jobs −

• To accept request from the device independent software above to it.
• Interact with the device controller to take and give I/O and perform required error handling
• Making sure that the request is executed successfully - How a device driver handles a request is as follows: Suppose a request comes to read a block N.
• If the driver is idle at the time a request arrives, it starts carrying out the request immediately.
• Otherwise, if the driver is already busy with some other request, it places the new request in the queue of pending requests.

Device Drivers cont..

Protection and Security

► Protection – any mechanism for controlling access of processes or users to resources defined by the OS

► Security – defense of the system against internal and external attacks

► Huge range, including denial-of-service, worms, viruses, identity theft, theft of service

► Systems generally first distinguish among users, to determine who can do what ► User identities (user IDs , security IDs) include name and associated number, one per user ► User ID then associated with all files, processes of that user to determine access control ► Group identifier (group ID ) allows set of users to be defined and controls managed, then also associated with each process, file ► Privilege escalation allows user to change to effective ID with more rights

• The batch processing operating system is capable of

executing one job at a time.

• In batch processing operating system the jobs are

combined in form of batch and then these batches are

given to system as an input data.

• The job in batches are processed on first come first

serve basis.

• After execution of one job operating system fetches

another job from input data.

• There is no need of human interaction before fetching

the next job after completion of any job.

Batch processing operating system

Atul Choudhary - Operating System (Silberschatz, Galvin, Operating SystemConcepts) * 19

• The multi user operating system uses to use a

system by multiple users.

• In other word multi user operating system allows a

number of users to work simultaneously on a single

computer system.

• These types of operating systems are specially

designed for the multi user system.

• Examples of multi user operating systems includes

Unix, Linux, Windows 2000 and VM – 386.

Multi user operating system

Atul Choudhary - Operating System (Silberschatz, Galvin, Operating SystemConcepts) * 20