OPERATING SYSTEMS

- K.R.VASISTHA- 11EE01009- 2ND YEAR - SCHOOL OF ELECTRICAL SCIENCES- IIT BHUBANESHWAR

UNDER THE SUPERVISION OF DR. C.N.BHENDE-

WHAT IS AN OPERATING SYSTEM?

An operating system (OS) is a collection of software that manages computer hardware resources and provides common services for computer programs.

The operating system is a vital component of the system software in a computer system.

Application programs require an operating system to function.

It manages all other programs on the machine.

It is present in almost any device that has computational capabilities.

Examples of popular, modern operating systems include Android, BSD, iOS, Linux, Mac OS X, Microsoft Windows, IBM z/OS.

TYPES OF OPERATING SYSTEMS

1. Single user - single task. Ex:- mobile OS

2. Multi user – multi task. Ex:- Unix, Linux

3. Real time. Ex:-industrial systems,machinery

4. Single user – multi tasking. Ex:- Windows

5. Distributed. Ex:- networked computers

6. Embedded. Ex:- Windows CE, Minix 3

Which OS to use?

Operating systems provide a software platform on top of which other programs can run.

Application software is written to run on a specific OS, sometimes even on specific hardware.

So, one’s choice of OS depends on what type of programs he wants to run.

Most common OS’s are :- Windows, Mac OS X and Linux.

WHAT DOES AN OPERATING SYSTEM DO?

It performs basic tasks such as:

Recognising input from keyboard and mouse. Sending output to the monitor.

keeping track of files and directories on the disk.

Controlling peripheral devices such as disk drives and printers.

Time-sharing operating systems schedule tasks for efficient use of the system.

There are various functions that are needed to be performed by an OS.

Functions of an operating system

1. Memory management

2. User interface

3. Security

4. Networking

5. Program execution and interruption

6.Multitasking

7. File directories and drivers storage and management

Components of an operating system

1. Networking

2. Security

3. Kernel

4. User Interface

Components of an operating system

Networking :-Computers running different operating systems are able to share resources using either wired or wireless connections.

Security :-To verify the identity of a user, authentication is required which demands authorisation. Operating systems provide security through firewalls. Passwords and/or bio-metric/other data may be required for verification of identity.

Kernel

• A kernel connects the application software to the hardware of a computer.

• With the aid of the firmware and device drivers, the kernel provides the most basic level of control over all of the computer's hardware devices.

Program execution :-Executing an application program involves a process by the kernel which initiates execution of the application program which then interacts with the user and with hardware devices.

Modes :-CPUs have at least two modes: protected mode and supervisor mode.

• The use of virtual memory addressing (such as paging or segmentation) means that the kernel can choose what memory each program may use at any given time, allowing the operating system to use the same memory locations for multiple tasks.

Multitasking :-•  Since most computers can do at most one or two things at one time,

this is generally done via time-sharing, which means that each program uses a share of the computer's time to execute.

• An operating system kernel contains a piece of software called a scheduler which determines how much time each program will spend executing, and in which order execution control should be passed to programs.

Disk access and file systems :-• Access to data stored on disks is a central feature of all

operating systems. The specific way in which files are stored on a disk is called a file system.

• Partitioning of disk drives is key feature of modern OS. • A connected storage device can be accessed through a device driver.

Out of the in numerous files and directories in a system, an OS keeps the most used files/ directories as temporary or cache files for ready access thus reducing the time taken for the process and exerting less drain on system resources.

User interface

• The U.I is not generally a part of an OS but runs in a separate program called shell/grub.

• The two most common forms are

Command line interface

• Commands are typed line by line.

Graphical user interface

• Visual environment is present.

What happens when we power on a computer?

Bootstrap loader

• The bootstrap loader is a small program that has a single function: It loads the operating system into memory and allows it to begin operation.

• The bootstrap loader sets up the small driver programs that interface with and control the various hardware.

• It sets up the divisions of• memory• user information, and• applications.

• It establishes the data structures needed to communicate within and between the subsystems and applications of the computer.

• Then it turns control of the computer over to the operating system.

THANK

YOU