Amity School of Engineering & Technology · 2016-07-18 · 10 The working of Operating System OS is...

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Operating SystemsTopic: Operating System Definition & its functions

ANIL SAROLIYA

Amity School of Engineering Technology

B.Tech.(CSE) & B.Tech (IT) 3rd Semester

Amity School of Engineering & Technology

B.Tech (CSE)/B.Tech(IT) 3rd Semester

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Text/ Reference Books



Text Books:

Silberschatz A. , Galvin P.B., Operating System Concepts, 7th ed. (2006), JohnWilley & Sons.INC

Milenekovic, Operating System Concepts, 4nd ed.(2002), McGraw Hill

Reference Books:

Stallings W., Operating System, 6th ed. (2009), Pearson

Gary N., Operating System, A Modern Perspection,3rd ed.(2000), Pearson Edu.

Tanenbaum A. S., Modern Operating System, 5th ed.(2006), PHI.

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Module I: Introduction to operating system

Operating system and function

Evolution of operating system:– Batch

– Interactive,

– multiprogramming,

– Time Sharing and Real Time System,

– multiprocessor system,

– Distributed system,

– System protection.

Operating System structure

Operating System Services

System Program and calls



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What is an Operating System?The collection of software which administers, maintains and

provides access to the resources of a computer system, is called

the Operating system.

It is the one of the type of system software

It is like a cop (policeman), it makes sure that different

program and users running at the same time do not interfere

with each other.

The operating system is also responsible for security, ensuring

that unauthorized users do not access the system.

Operating systems provide a software platform on top of which

other programs, called application programs, can run.



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Well known Example of Operating System:

Windows XP Professional (or Home) Edition,

Windows Vista,

Windows 2003(use to run the server),

Unix,

Linux,

Solaris,

Apple-Mac, etc.



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Operating system goals:

Execute user programs and make solving userproblems easier.

Make the computer system convenient to use.

How to use the computer hardware in an efficientmanner



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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 variousapplications and users

– Application programs – define the ways in which thesystem resources are used to solve the computingproblems of the users

• Word processors, compilers, web browsers, databasesystems, video games

– Users

• People, machines, other computers

Computer System Structure(contd..) : Four Components of a Computer System

Operating System

Computer

Hardware

User 1 User 2 User 3 User N

Compiler assembler Text editor Database

System

System and application programs

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Technical definition of OS

• Resource allocator – manages and allocatesresources.

• Control program – controls the execution of userprograms and operations of I/O devices .



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The working of Operating System

OS is a program that manages a computer's resources

and performs basic tasks. Some of the working of OS

are as follows:

Recognizing keyboard input

Sending output to the display screen or printer

Managing files and directories

Controlling peripheral devices

Allocating system resources to other programs running on

the computer



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The working of Operating System(continued..)

Figure: The working of Operating System



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Important Term:

Kernel

It is a program which runs every time till the machine(mostly in

computers) is in active mode

As compare to other application programs, kernel always lies inside the

Memory(RAM).

Interrupt

It is the signal to a processor indicating that an asynchronous event has

occurred. Here the current sequence of instructions is temporarily

suspended, and a sequence related to the interruption is started in its place.

or

Its purpose is to alert the operating system when any special event occurs so

that it can suspend its current activity and deal appropriately with the new

situation



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Important Term: Interrupt (continued..)

So, we can say, that, Interrupting is a mechanism by which other

modules (I/O, memory) may interrupt the normal sequencing of

the processor (CPU) .

Interrupts help to improve processor utilization.

Classes of interrupts:

Program Interrupt: generated by some condition that occurs as a result of an

instruction execution, such as arithmetic overflow, division by zero, attempt to

execute an illegal machine instruction, and reference outside a user’s allowed

memory space.

Timer Interrupt: Generated by a timer within the processor. This allows the

operating system to perform certain functions regularly.

I/O Interrupt: Generated by an I/O controller, to signal normal completion of

an operation or to signal a variety of error conditions.

H/W failure Interrupt: Generated by a failure, such as power, etc.



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Main Functions of an OS

OS

Command Interpretation

or

User Interface

Protection and Security

Device Management

File Management

Memory Management

Process Management

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Main Functions of an OS (continued…)

Process Management

As we know OS controls the execution of applications.

Application (software) is made up by set of programs.

A process (also called job) is a program in execution.

OS manages the processes (which are submitted to a computer

system) in a manner to minimize idle time of processors (CPUs,

I/O processors, etc.) of the system

– Create, execute, delete process

– Cancel or resume process, schedule process

– Synchronization,

– Communication,

– Deadlock handling



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Memory Management

Memory is important resource of a computer system that

must be properly managed for the overall system

performance.

Memory management module:

Keeps the track of parts of memory in use and parts not in use

Allocates(provides) memory to processes as needed and de-

allocates when no longer needed



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Memory Levels: CPU Accessing

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Main Functions of an OS (continued…): File Management

A file is a collection of related information. Every file has a name, its

data and attributes

File’s name uniquely identifies the file in the system and is used by its users to

access itself

File’s data is the available as contents found in the file

File’s attributes contain information such as

– date & time file creation,

– date & time of last access,

– date & time of last update,

– its current size,

– its protection features, etc.

File management module of an operating system takes care of file-

related activities such as:– structuring(type of the file),

– accessing,

– naming,

– sharing,

– and protection of files

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Device (I/O) Management

Manages and controls devices attached to computer

Handles devices by both hardware and software techniques

I/O Hardware: Ports, buses, device controllers for devices

Software (Device driver): OS communicates with I/O hardware via device

driver of device

Device Controller

Operates port, bus, device. Bridge between device and OS

Complexity of handling devices is abstracted and hidden in device

drivers of device



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Security deals with protecting the various resources and information

of a computer system against destruction and unauthorized access

External security: Deals with securing computer against external factors

such as fires, floods, earthquakes, stolen disks/tapes, etc. by maintaining

adequate backup, using security guards, allowing access to sensitive information

to only trusted employees/users, etc.

Internal security: Deals with user authentication, access control, and

cryptography mechanisms

User authentication: Deals with the problem of verifying the identity of a user

(person or program) before permitting access to the requested resource

Access Control: Once authenticated, access control mechanisms prohibit a

user/process from accessing those resources/information that he/she/it is not

authorized to access

Cryptography: Means of encrypting private information so that unauthorized

access cannot use information

Back-up of data : Took the extra copy of essential data on another place of

same or other storage device or media.

Main Functions of an OS (continued…): SECURITY

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Command Interpretation: It provides a set of commands

using which the user can give instructions to the computer for

getting some job done by it

Two types of user interfaces(for command interpretation) supported by

various operating systems are: Command-line interface: User gives instructions to the computer by

typing the commands (console mode)

Graphical User Interface (GUI): User gives commands to the system

by selecting icon or menu item displayed on the screen with the use of a

point-and-draw device



Thanks

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Amity School of Engineering & Technology · 2016-07-18 · 10 The working of Operating System OS is...

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