5 Chapter 05 Operating Systems

65

Chapter -05

Operating Systems (OS)

Source: http://internetdblog.blogspot.com/2012/01/what-i-operating-system.html

Management Information Systems Page 66

Chapter 5 Operating Systems

5.1 Introduction to Operating Systems (OS)

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 usually

require an operating system to function.1

Operating Systems (abbreviated as "OS") is the program that, after being initially loaded into

the computer by a boot program, manages all the other programs in a computer. The other

programs are called applications or application programs. The application programs make

use of the operating system by making requests for services through a defined application

program interface (API). In addition, users can interact directly with the operating system

through a user interface such as a command language or a graphical user interface (GUI).

Figure 5.1 http://en.wikipedia.org/wiki/Process_management_%28computing%29

The operating systems (OS) consists of the master system of programs that manage the basic

operations of the computer, This program provide resource management services of many

kinds, handling such matters as running and storing programs and processing data.2

Time-sharing operating systems schedule tasks for efficient use of the system and may also

include accounting for cost allocation of processor time, mass storage, printing, and other

resources.3 For hardware functions such as input and output and memory allocation, the

operating system acts as an intermediary between programs and the computer hardware,

although the application code is usually executed directly by the hardware and will

frequently make a system call to an OS function or be interrupted by it. Operating systems

can be found on almost any device that contains a computerfrom cellular phones and video game consoles to supercomputers and web servers. Examples of popular modern operating

systems include Android, BSD, iOS, Linux, Mac OS X, Microsoft Windows, 4 Windows

Phone, and IBM z/OS. All these, except Windows and z/OS, share roots in UNIX.

An operating systems is similar to a government. The components of computer system are its

hardware, software, and data. The operating system provides the means for the proper use of

these resources in the operation of the computer systems. Like a government, the operating

systems performs no useful function by itself. It simply provides an environment within



which other programs can do useful work. An operating systems is an important part of

almost every computer systems. We can say that an operating system is a control program.

5.2 What is Operating System (OS)? Write importance of Operating Systems (OS).

An Operating System is a computer program that manages the resources of a computer. It

accepts keyboard or mouse inputs from users and displays the results of the actions and

allows the user to run applications, or communicate with other computers via networked

connections.

The operating system is the most important program that runs on a computer. Every general-

purpose computer must have an operating system to run other programs. Operating systems

perform basic tasks, such as recognizing input from the keyboard, sending output to the

display screen, keeping track of files and directories on the disk, and controlling peripheral

devices such as disk drives and printers. Importances of Operating Systems are follows:

1. It moderates the relationship between the computer and its peripherals

2. It helps in the management of files,- copying, deleting, moving of files from one storage

location to the other.

3. It encourages the memory for its efficient usage and thus adding the speed of the

computer.

4. It manages the activities of the processor in terms of job execution according to the

priority of arrival, of jobs

5. It informs the user of nay hardware or software error

6. It makes communication between the computer and the user or the operator possible.

Figure 5.2 http://en.wikipedia.org/wiki/Process_management_%28computing%29

We can view an operating system as a resource allocator. An operating system (OS) is a software

program, but it is different from word processing program, spreadsheets, and all the other

software programs on your computer. It is the master control program.

a) The operating system provides the means for the proper use of these resources in the

operating of the computer systems.

b) It is similar to a government.

c) It simply provides an environment within which other programs can do useful work.



d) We can view an operating system as a resource allocator.

e) The fundamentals goal of computer systems is to execution user programs to make

solving user problems easier.

f) The secondary goal is efficient operation of the computer systems.

5.3 Define Operating Systems. Write functions of Operating Systems (OS). Explain.

An operating system is a group of computer programs that coordinates all the activities among

computer hardware devices. It is the first program loaded into the computer by a boot program

and remains in memory at all times.

The basic functions of an operating system are:

i. Booting the computer ii. Coordinate processing

iii. Manage the use of RAM (main memory) iv. Allocates use of peripheral devices v. Checks all equipments and display error messages.

vi. Manages files stored on disk. (save) vii. Manages files open from disk. (open)

Figure 5.3 http://en.wikipedia.org/wiki/Operating_system#BSD_and_its_descendants



Booting the computer

The process of starting or restarting the computer is known as booting. A cold boot is when you

turn on a computer that has been turned off completely. A warm boot is the process of using the

operating system to restart the computer.

Performs basic computer tasks

The operating system performs basic computer tasks, such as managing the various peripheral

devices such as the mouse, keyboard and printers. For example, most operating systems now are

plug and play which means a device such as a printer will automatically be detected and

configured without any user intervention.

Provides a user interface

A user interacts with software through the user interface. The two main types of user interfaces

are: command line and a graphical user interface (GUI). With a command line interface, the user

interacts with the operating system by typing commands to perform specific tasks. An example

of a command line interface is DOS (disk operating system). With a graphical user interface, the

user interacts with the operating system by using a mouse to access windows, icons, and menus.

An example of a graphical user interface is Windows Vista or Windows 7.

The operating system is responsible for providing a consistent application program interface

(API) which is important as it allows a software developer to write an application on one

computer and know that it will run on another computer of the same type even if the amount of

memory or amount of storage is different on the two machines.

Handles system resources

The operating system also handles system resources such as the computer's memory and sharing

of the central processing unit (CPU) time by various applications or peripheral devices. Programs

and input methods are constantly competing for the attention of the CPU and demand memory,

storage and input/output bandwidth. The operating system ensures that each application gets the

necessary resources it needs in order to maximize the functionality of the overall system.

Provides file management

The operating system also handles the organization and tracking of files and directories (folders)

saved or retrieved from a computer disk. The file management system allows the user to perform

such tasks as creating files and directories, renaming files, coping and moving files, and deleting

files. The operating system keeps track of where files are located on the hard drive through the

type of file system. The type two main types of file system are File Allocation table (FAT) or

New Technology File system (NTFS).

5.4 Write different types of File System. Explain.



In computing, a file system is used to control how information is stored and retrieved. Without a

file system, information placed in a storage area would be one large body of information with no

way to tell where one piece of information stops and the next begins.

By separating the information into individual pieces, and giving each piece a name, the

information is easily separated and identified. Taking its name from the way paper based

information systems are named, each piece of information is called a "file". The structure and

logic rules used to manage the groups of information and their names is called a "file system".

There are many different kinds of file systems. Each one has different structure and logic. Each

one has different properties of speed, flexibility, security, size and more. Some file systems have

been designed to be used for specific applications. For example the ISO 9660 file system is

designed specifically for optical disks.

File systems can be used on many different kinds of storage devices. Each storage device uses a

different kind of media. The most common storage device in use today is a hard drive whose

media is a disc that has been coated with a magnetic film. The film has ones and zeros 'written'

on it sending electrical pulses to a magnetic "read-write" head. Other media that are used are

magnetic tape, optical disc, and flash memory. In some cases, the computer's main memory

(RAM) is used to create a temporary file system for short term use.

File systems are used to implement type of data store to store, retrieve and update a set of files.

"File system" refers to either the abstract data structures used to define files, or the actual

software or firmware components that implement the abstract ideas.

File Allocation table (FAT) uses the file allocation table which records, which clusters are used

and unused and where files are located within the clusters.

NTFS is a file system introduced by Microsoft and it has a number of advantages over the

previous file system, named FAT32 (File Allocation Table).

One major advantage of NTFS is that it includes features to improve reliablity. For example, the

new technology file system includes fault tolerance, which automatically repairs hard drive

errors without displaying error messages. It also keeps detailed transaction logs, which tracks

hard drive errors. This can help prevent hard disk failures and makes it possible to recover files if

the hard drive does fail.

Some file systems are used on local data storage devices; others provide file access via a network

protocol (e.g. NFS, SMB, or 9P clients). Some file systems are "virtual", in that the "files"

supplied are computed on request (e.g. procfs) or are merely a mapping into a different file

system used as a backing store. The file system manages access to both the content of files and

the metadata about those files. It is responsible for arranging storage space; reliability, efficiency,

and tuning with regard to the physical storage medium are important design considerations.

Types of file system are:

File Allocation table (FAT)

New Technology file system (NTFS)



NTFS also allows permissions (such as read, write, and execute) to be set for individual

directories and files.

Figure 5.4 http://en.wikipedia.org/wiki/Operating_system#

Time-sharing operating systems schedule tasks for efficient use of the system and may also

include accounting for cost allocation of processor time, mass storage, printing, and other

resources.

For hardware functions such as input and output and memory allocation, the operating system

acts as an intermediary between programs and the computer hardware, although the application

code is usually executed directly by the hardware and will frequently make a system call to an

OS function or be interrupted by it. Operating systems can be found on almost any device that

contains a computerfrom cellular phones and video game consoles to supercomputers and web servers.

Examples of popular modern operating systems include Android, BSD, iOS, Linux, Mac OS X,

Microsoft Windows, Windows Phone, and IBM z/OS. All these, except Windows and z/OS,

share roots in UNIX.

5.5 Write different types of Operating Systems.

There are different types of operating systems has been using in the world like:-

a) Real-time Operating Systems b) Multi-user Operating Systems c) Multi-tasking Operating Systems d) Time Sharing Operating Systems



e) Distributed operating Systems

Figure 5.5 http://en.wikipedia.org/wiki/Operating_system#Components

a) Real-time operating systems

A real-time operating system is a multitasking operating system that aims at executing real-time

applications. Real-time operating systems often use specialized scheduling algorithms so that

they can achieve a deterministic nature of behavior. The main objective of real-time operating

systems is their quick and predictable response to events. They have an event-driven or time-

sharing design and often aspects of both. An event-driven system switches between tasks based

on their priorities or external events while time-sharing operating systems switch tasks based on

clock interrupts.5

b) Multi-user operating systems

A multi-user operating system allows multiple users to access a computer system at the same

time. Time-sharing systems and Internet servers can be classified as multi-user systems as they

enable multiple-user access to a computer through the sharing of time. Single-user operating

systems have only one user but may allow multiple programs to run at the same time.

c) Multi-tasking vs. Single tasking operating systems

A multi-tasking operating system allows more than one program to be running at a time, from

the point of view of human time scales. A single-tasking system has only one running program.

Multi-tasking can be of two types: pre-emptive or co-operative. In pre-emptive multitasking, the

operating system slices the CPU time and dedicates one slot to each of the programs. Unix-like

operating systems such as Solaris and Linux support pre-emptive multitasking, as does Amiga

OS. Cooperative multitasking is achieved by relying on each process to give time to the other

processes in a defined manner. 16-bit versions of Microsoft Windows used cooperative multi-

tasking. 32-bit versions, both Windows NT and Win9x, used pre-emptive multi-tasking. Mac OS

prior to OS X used to support cooperative multitasking.



d) Time sharing operating systems

Time sharing is a logical extension of multiprogramming. Multiple jobs are executed by the CPU

switching between them, but the switches occur so frequently that the users may interact with each

program while it is running.

The time sharing systems were developed to provide interactive use of a computer system at a

reasonable cost. A time-sharing opening system uses CPU scheduling and multiprogramming to provide

each user with a small portion of a time shared computer. Each user has at least one separate program

in memory. A program that is loaded onto memory and is executing is commonly referred to as a

process.

f) Distributed operating systems

A distributed operating system manages a group of independent computers and makes them appear to

be a single computer. The development of networked computers that could be linked and communicate

with each other gave rise to distributed computing. Distributed computations are carried out on more

than one machine. When computers in a group work in cooperation, they make a distributed system.

There is a variety of reason for building distributed systems, the major ones being these:

a) Resource sharing

b) Computation speedup

c) Reliability

d) Communication

5.6 History of Operating Systems

Early computers were built to perform a series of single tasks, like a calculator. Operating

systems did not exist in their modern and more complex forms until the early 1960s. Basic

operating system features were developed in the 1950s, such as resident monitor functions that

could automatically run different programs in succession to speed up processing. Hardware

features were added that enabled use of runtime libraries, interrupts, and parallel processing.

When personal computers became popular in the 1980s, operating systems were made for them

similar in concept to those used on larger computers.6



Figure 5.6 http://en.wikipedia.org/wiki/Operating_system#Components

In the 1940s, the earliest electronic digital systems had no operating systems. Electronic systems

of this time were programmed on rows of mechanical switches or by jumper wires on plug

boards. These were special-purpose systems that, for example, generated ballistics tables for the

military or controlled the printing of payroll checks from data on punched paper cards. After

programmable general purpose computers were invented, machine languages (consisting of

strings of the binary digits 0 and 1 on punched paper tape) were introduced that sped up the

programming process.

5.7 Write different types of Operating Systems (OS) with examples.

World most popular Operating Systems are:

1. Windows (Desktop Operating Systems) 2. Unix (Server Operating Systems) 3. Mac/OS (Apple computer Operating Systems) 4. iPhone : Mobile Operating Systems:

1. Windows: (Desktop Operating Systems)

Example: Windows 95, Windows 2000, Windows 2003, Windows XP, Vista, Windows 7, and 8 etc.

Microsoft Windows is a series of graphical user interface (GUI) operating systems developed,

marketed, and sold by Microsoft. Microsoft introduced an operating environment named

Windows on November 20, 1985 as a graphical operating system shell for MS-DOS in response

to the growing interest in graphical user interfaces (GUI). Microsoft Windows came to dominate

the world's personal computer market with over 90% market share, overtaking Mac OS, which

had been introduced in 1984.

As of September 2013, the most recent versions of Windows for personal computers, mobile

devices, server computers and embedded devices are respectively Windows 8, Windows Phone

8, Windows Server 2012 and Windows Embedded 8.



Windows XP

The next major version of Windows, Windows XP, was released on October 25, 2001. The

introduction of Windows XP aimed to unify the consumer-oriented Windows 9x series with the

architecture introduced by Windows NT, a change which Microsoft promised would provide

better performance over its DOS-based predecessors. Windows XP would also introduce a

redesigned user interface (including an updated Start menu and a "task-oriented" Windows

Explorer), streamlined multimedia and networking features, Internet Explorer 6, integration with

Microsoft's .NET Passport services, modes to help provide compatibility with software designed

for previous versions of Windows, and Remote Assistance functionality.

Windows Vista, 7 and 8

After a lengthy development process, Windows Vista was released on November 30, 2006 for

volume licensing and January 30, 2007 for consumers. It contained a number of new features,

from a redesigned shell and user interface to significant technical changes, with a particular

focus on security features. It was available in a number of different editions, and has been subject

to some criticism. Vista's server counterpart, Windows Server 2008 was released in early 2008.

On July 22, 2009, Windows 7 and Windows Server 2008 R2 were released as RTM (release to

manufacturing) while the former was released to the public 3 months later on October 22, 2009.



Unlike its predecessor, Windows Vista, which introduced a large number of new features,

Windows 7 was intended to be a more focused, incremental upgrade to the Windows line, with

the goal of being compatible with applications and hardware with which Windows Vista was

already compatible. Windows 7 has multi-touch support, a redesigned Windows shell with an

updated taskbar, a home networking system called Home Group, and performance

improvements.

Windows 8, the successor to Windows 7, was released generally on October 28, 2012. A number

of significant changes were made on Windows 8, including the introduction of a user interface

based around Microsoft's Metro design language with optimizations for touch-based devices

such as tablets and all-in-one PCs. These changes include the Start screen, which uses large tiles

that are more convenient for touch interactions and allow for the display of continually updated

information, and a new class of apps which are designed primarily for use on touch-based

devices. Other changes include increased integration with cloud services and other online

platforms (such as social networks and Microsoft's own SkyDrive and Xbox Live services), the

Windows Store service for software distribution, and a new variant known as Windows RT for

use on devices that utilize the ARM architecture.

2. UNIX: (Server Operating Systems)

Example: Linux, Fedora Linux, Red hat Linux, HP-Unix, and IBM-UX etc.

Figure 5.7 http://en.wikipedia.org/wiki/UNIX

UNIX was originally written in assembly language. Ken Thompson wrote B, mainly based on

BCPL, based on his experience in the MULTICS project. B was replaced by C, and Unix,

rewritten in C, developed into a large, complex family of inter-related operating systems which

have been influential in every modern operating system.

The UNIX-like family is a diverse group of operating systems, with several major sub-categories

including System V, BSD, and Linux. The name "UNIX" is a trademark of The Open Group

which licenses it for use with any operating system that has been shown to conform to their

definitions. "UNIX-like" is commonly used to refer to the large set of operating systems which

resemble the original UNIX.



Unix-like systems run on a wide variety of computer architectures. They are used heavily for

servers in business, as well as workstations in academic and engineering environments. Free

UNIX variants, such as Linux and BSD, are popular in these areas.

Four operating systems are certified by the Open Group (holder of the Unix trademark) as Unix.

HP's HP-UX and IBM's AIX are both descendants of the original System V Unix and are

designed to run only on their respective vendor's hardware. In contrast, Sun Microsystems's

Solaris Operating System can run on multiple types of hardware, including x86 and Sparc

servers, and PCs. Apple's Mac OS X, a replacement for Apple's earlier (non-Unix) Mac OS, is a

hybrid kernel-based BSD variant derived from Next STEP, Mach, and FreeBSD.

Unix interoperability was sought by establishing the POSIX standard. The POSIX standard can

be applied to any operating system, although it was originally created for various Unix variants.

What is Linux?

Linux is, in simplest terms, an operating system. It is the software on a computer that enables

applications and the computer operator to access the devices on the computer to perform desired

functions. The operating system (OS) relays instructions from an application to, for instance, the

computer's processor. The processor performs the instructed task, then sends the results back to

the application via the operating system. Explained in these terms, Linux is very similar to other

operating systems, such as Windows and OS X.

But something sets Linux apart from these operating systems. The Linux operating system

represented a $25 billion ecosystem in 2008. Since its inception in 1991, Linux has grown to

become a force in computing, powering everything from the New York Stock Exchange to

mobile phones to supercomputers to consumer devices.

As an open operating system, Linux is developed collaboratively, meaning no one company is

solely responsible for its development or ongoing support. Companies participating in the Linux

economy share research and development costs with their partners and competitors. This

spreading of development burden amongst individuals and companies has resulted in a large and

efficient ecosystem and unheralded software innovation.

Over 1,000 developers, from at least 100 different companies, contribute to every kernel release.

In the past two years alone, over 3,200 developers from 200 companies have contributed to the

kernel--which is just one small piece of a Linux distribution.

3. Mac/OS

Example: Apple computer Operating Systems (Macintosh/OS)

Mac OS is a series of graphical user interface-based operating systems developed by Apple Inc.

for their Macintosh line of computer systems. The original version was the integral and unnamed

system software first introduced in 1984 with the original Macintosh, and referred to simply as

the "System" software. The System was renamed to Mac OS in 1996 with version 7.6. The

System is credited with popularizing the graphical user interface concept.



Mac OS releases have existed in two major series. Up to major revision 9, from 1984 to 2000, it

is historically known as Classic Mac OS. Major revision 10 (revisioned minorly, such as 10.0

through 10.9), from 2001 to present, has had the brand name of Mac OS X and now OS X. Both

series share a general interface design and some shared application frameworks for

compatibility, but also have deeply different architectures.

4. iPhone : Mobile Operating Systems:

Example : iPhone, RIM, Windows, Palm, Android, and Hiptop.

An abbreviated list of some of the popular electronic devices Linux is used on today includes:

Dell Inspiron Mini 9 and 12

Garmin Nuvi 860, 880, and 5000

Google Android Dev Phone 1

HP Mini 1000

Lenovo IdeaPad S9

Figure 5.8http://en.wikipedia.org/wiki/UNIX



Questions

1. Define Operating Systems (OS).

2. What are the differences among Windows, UNIX, and MAC/OS? Explain.

3. Discuss the functions of Operating Systems (OS). in MIS.

4. Explain the role of Operating Systems (OS) in MIS

5. Mention the importance of Operating Systems (OS).

6. How would you like to define Operating Systems (OS)? What are the functions of Time sharing, Real- time and Multitasking operating systems ?

7. Write different examples of Operating Systems. Write different types of Operating Systems (OS).

Explain.

8. Write functions of Operating Systems (OS). Explain.

9. What are Operating Systems? Write functions of Operating Systems (OS) with example.

Reference

1 http://en.wikipedia.org/wiki/System_software

2 Hutchinson, et. el (2003), Computer and Information Systems, USA: IRWIN. p.197

3 http://en.wikipedia.org/wiki/Time-sharing

4 "Operating System Market Share". Net Applications. Hansen, Per Brinch, ed. (2001). Classic Operating Systems. Springer.

5 http://en.wikipedia.org/wiki/Real-time_operating_system

6 http://en.wikipedia.org/wiki/Operating_system#Types_of_operating_systems

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5 Chapter 05 Operating Systems