PRESENTED BY:1.RAHMAN, MAHMUDA (13-22990-1)2. ZAMAN, MARDIA (12-23072-3)3. MONIJA, SAYEDA SHIPARIN (13-23072-1)

WELCOME to OurPresentation on Operating System & its Components…….

WHAT IS AN OPERATING SYSTEM? Its is a collection of software

that manages computer hardware resources and provides common services for computer programs.

A vital component of the system and operates all other program software in a computer system.

It was developed for better computer usage and providing better platform to the users application.

CLASSIFICATION OF OS Multi-user: Allows two or

more users to run programs at the same time.

Multiprocessing: Supports running a program on more than one CPU.

Multitasking: Allows more than one program to run concurrently.

Multithreading: Allows different parts of a single program to run concurrently.

Real time: Responds to input instantly. General-purpose operating systems, such as DOS and UNIX, are not real-time. FIG 1: multi-user OS

FIG 2: multiprocessing OS

ROLE OF OPERATING SYSTEM Management of the processor - Scheduling algorithm. Management of the random access memory(RAM) – Virtual

memory.

Management of input/output - Peripheral administrators or input/output administrators.

Management of execution of applications - Allocating the resources required.

Management of authorizations - Security relating to execution of programmers.

File management - Reading and writing in the file system. - File access authorizations.

Information management - Provides a certain number .

BOOTSTRAP PROCESSBooting includes four main steps in computer

including power On.1. Turn on computer . 2. load the initial instructions from the ROM .3. detect the operating system in the Hard-disk.4. start the certain essential computer application

as per the default setting.

FIG 3: Bootstrap Steps

OS COMPONENTSThe operating system can be broken down into four

main parts. They are: Kernel Device Drivers User Interface System Utilities.

KERNEL: kernel handles User interface Memory management Program Execution or process management Device management. File management Data security

FIG 4: Kernel’s Operations

USER INTERFACE: Each operating system has a user interface, a program

that accepts requests from users (processes) and interprets them for the rest of the operating system.  The two most common forms of a user interface have historically been the command-line interface, where computer commands are typed out line-by-line, and the graphical user interface, where a visual environment (most commonly wimp) is present. A user interface in some operating systems, such as UNIX, is called a shell. In others, it is called a window to denote that it is menu driven and has a GUI (graphical user interface) component.

MEMORY MANAGER Memory management is the functionality of an

operating system which handles or manages primary memory. Memory management keeps track of each and every memory location either it is allocated to some process or it is free. It checks how much memory is to be allocated to processes. Operating systems can be divided into two broad categories of memory management: mono programming and multiprogramming.

FIG 5(a): mono programming FIG 5(b): multiprogramming

MULTIPROGRAMMING

Partitioning: In personal computers, a partition is a logical division of a hard disk created so that you can have different operating systems on the same hard disk or to create the appearance of having separate hard drives for file management, multiple users, or other purposes.

Paging:  paging is one of the memory management schemes by which a computer stores and retrieves data from the secondary storage for use in main memory

Demand paging :its a method of virtual memory management copies a disk page into physical memory only if an attempt is made to access it and that page is not already in memory (i.e., if a page fault occurs).

Demand segmentation: it is used when insufficient hardware to implement demand paging. Segment descriptor contains a valid bit to indicate whether the segment is currently in memory.

If segment is in main memory, access continues,

If not in memory, segment fault.

FIG 6 : multiprogramming

PROCESS MANAGER Process management is an integral part of any modern day operating system. It is

the second function of an operating system . The OS must allocate resources to processes, enable processes to share and exchange information, protect the resources of each process from other processes and enable synchronization among processes. The relationship between a program, a job and a process becomes clearer if we consider how a program becomes a job and how a job becomes a process

A program is a non-active set of instructions stored on disk.

A program becomes a job from the moment it is selected for execution until it has finished running and becomes a program again.

A process is a program in execution. It is a program that has started but has not finished.

Scheduler :To move a job or process from one state to another, the process manager uses two schedulers: the job scheduler and the process scheduler.

Process synchronization has two problematic situations: deadlock and starvation.

Deadlock: Deadlock occurs when the operating system does not put resource restrictions on processes.

Starvation: occurs when operating system puts too many resource restrictions on a process.

DEVICE MANGER FILE MANAGER

Keep tracks of all devices. Program responsible for this task is known as the I/O controller.

Decides which process gets the device when and for how much time.

Allocate the device in the efficient ways.

De-allocates devices

controls access to files. supervises the creation,

deletion, and modification of files.

controls the naming of files.

supervises the storage of files.

is responsible for archiving and backups.

DATA SECURITY A computer being secure depends ona number of technologies working properly. A modern operatingsystem provides access to a number of resources, which are available tosoftware running on the system, and to external devices like networks via the kernel. The operating systemmust be capable of distinguishing between requests which should be allowed to be Processed, and others which should not be processed. Inaddition to allow or disallow modelof security system with a high levelof security also offers auditingoptions.

Fig 7 : Data security system model

LINUXLinux is one of popular version of UNIX operating System. It is opensource as its source code is freely available. It is free to use. Linux

wasdesigned considering UNIX compatibility. It's functionality list is quitesimilar to that of UNIX. Linux Operating System has primarily three components: Kernel - Provides the required abstraction to hide low level hardware. System Utility - System Utility programs are responsible to do specialized, individual level tasks. System Library - libraries implements most of the functionalities of the operating system.

Fig 8: Linux OS Components

The booting process in Linux is quite different than windows except the

BIOS and MBR features. There are some basic steps in Linux operating

system while booting. The first process starting when you turn on your

computer is BIOS ( Basic Input Output System).

LINUX BOOTING STEPS

FIG 9: LINUX Booting Steps

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