software definition

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Software Definition

Software is the name given to the computer programs that instruct the hardware

how to work. Software are the instructions in the form of programs which controlthe operation of a computer, together with the associated documentation. Without

software, the computer would do absolutely nothing.

System Software

System software is the background programs that control a computer system.

System Software acts as a mediator between application programs and the

computer system’s hardware, as well as between the PC and the user.

Types of System Software

There are two basic types of operating systems:

Single program and Multitasking.

A single program operating system allows only one program to run at a time. This

means that if you are working in a spreadsheet and want to write a memo, you

must shut down the spreadsheet application and open up a word processor. Thisis annoying, especially if you need to quote some data from the spreadsheet in

your memo! So new operating systems were designed that allowed multiple

programs to run at the same time.

The simplest form is multi-tasking. What this really means is that the programs

are taking turns with the processor. It allows a single user to have the

spreadsheet and the word processor open at the same time, and even more.

Now the user can see to copy data from one to the other. Much better!!

The computer must decide on how many time slices each program gets. The

active program gets the most. Next is programs that are doing things but which

aren't the foreground program. Last is programs that are open but aren't doing

anything. They need a little bit of time every now and then to see if they are

supposed to do something yet.



Functions of Operating System

Allocating System Resources

The operating system directs the traffic inside the computer, deciding what

resources will be used and for how long. Time in the CPU is divided into time slices which are measured in milliseconds.

Each task the CPU does is assigned a certain number of time slices. When time

expires, another task gets a turn. The first task must wait until it has another turn.

Since time slices are so small, you usually can't tell that any sharing is going on.

Tasks can be assigned priorities so that high priority (foreground) tasks get more

time slices than low priority (background) tasks.

Memory must be managed also by the operating system. All those rotating turns

of CPU use leave data waiting around in buffers. Care must be taken not to lose

data!! One way to help out the traffic jam is to use virtual memory. This includes

disk space as part of main memory. While it is slower to put data on a hard disk,

it increases the amount of data that can be held in memory at one time. When

the memory chips get full, some of the data is paged out to the hard disk. This is

called swapping. Windows uses a swap file for this purpose.

Flow control is also part of the operating system's responsibilities. The operating

system must manage all requests to read data from disks or tape and all writes to

these and to printers.

To speed up the output to printers, most operating systems now allow for print

spooling, where the data to be printed is first put in a file. This frees up the

processor for other work in between the times data is going to the printer. A

printer can only handle so much data at a time. Without print spooling you'd have

to wait for a print job to finish before you can do anything else. With it you can

request several print jobs and go on working. The print spool will hold all the

orders and process them in turn.



Monitoring System Activities

A user or administrator can check to see whether the computer or network is

getting overloaded. Changes could be made to the way tasks are allocated or

maybe a shopping trip is in order! System performance would include response

time ( how long it takes for the computer to respond when data is entered) and

CPU utilization (comparing the time the CPU is working to the time it is idle.)

Some system security is part of the operating system, though additional software

can add more security functions. For multiple users who are not all allowed

access to everything, there must be a logon or login procedure where the user

supplies a user name or ID and a secret password. An administrator must set

up the permissions list of who can have access to what programs and what data.

File and Disk Management

Keeping track of what files are where is a major job. If you can't find a file, it

doesn't help to know that it is safe and secure somewhere. So an operating

system comes with basic file management commands. A user needs to be able

to create directories for storing files. (Dumping everything in one pile soon

becomes the needle-in-the-haystack story.) A user needs to copy, move, delete,

and rename files. This is the category of operating system functions that the user

actually sees the most.

A more technical task is that of disk management. Under some operating

systems your hard disk can be divided up, or partitioned into several virtual disks.

The operating system treats each virtual disk as though it were a physically

separate disk. Managing several physical and/or virtual disks can get pretty

complex, especially if some of the disks are set up with different operating

systems. (Some folks are never satisfied with just one of anything!)



Features of Operating System

There are many types of Operating System. For example Solaris Operating

System. The features are:

SecuritySolaris 10 includes some of the world's most advanced security features, such as

Process and User Rights Management, Trusted Extensions for Mandatory Access

Control, the Cryptographic Framework and Secure By Default Networking that

allow you to safely deliver new solutions, consolidate with security and protect

mission-critical data.

Observability

The Solaris 10 release gives you observability into your system with tools such as

Solaris Dynamic Tracing (DTrace), which enables real-time application debugging

and optimization.

Performance

Solaris 10 delivers indisputable performance advantages for database, Web, and

Java technology-based services, as well as massive scalability, shattering world

records by delivering unbeatable price/performance advantages.

Networking

With its optimized network stack and support for today’s advanced network

computing protocols, Solaris 10 delivers high-performance networking to most

applications without modification.

Data Management

Solaris 10 offers dramatic advances in file system and volume management by

delivering virtually unlimited capacity and near-zero administration.

Availability

New Solaris 10 features, such as Predictive Self Healing, support automatic

diagnosis and recovery from hardware and application faults, maximizing system

uptime.



Types of Operating System

When you purchase a new computer or mobile device, it typically has an

operating system preinstalled. As new versions of the operating system are

released, users upgrade their existing computers and mobile devices to

incorporate features of the new version. Purchasing an operating system upgrade

usually costs less than purchasing the entire iperating system. There are 3 type

of operating system commonly used:

Stand-Alone Operating System

A stand-alone operating system is a complete operating system that works on a

desktop somputer, notebook computer, or mobile computing device. Somestand-alone operating systems are caled client operating systems because they

also work in conjunction with a server operating system. Client operating systems

can operate with or without a network. Other stand-alone operating systems

include networking capabilities, allowing the home and small business user to set

up a small network. Examples of currently used stand-alone operating systems

are Windows Vista, Mac OS C, UNIC and Linux.

Embedded Operating Systems

The operating system on most mobile devices and many consumer electronics,

called an embedded operating system, resides on ROM chip. Popular embedded

operating systems include Windows Embedded CE, Windows Mobile, Palm OS,

iPhone OS, BlackBerry, Embedded Linux and Symbiam OS.

Server Operating System

A server operating system is an operating system that is designed specifically to

support a network. A server operating system typically resides on a server. The

client computers on the network rely on the server for resources. Server operating

systems are designed specifically to support all sizes of networks, including

medium- to large-sezed businesses and Web servers. Examples of server

operating systems include Windows Server 2008, UNIX, Linux, Solaris and

NetWare.



Popular Operating Systems

The most popular microcomputer operating systems are DOS, Windows 3.x,

Windows 95, OS/2, Windows NT, and Macintosh System. UNIX is a popular

operating system that is available for microcomputers, minicomputers, and

mainframe computer systems. The following will show the details:

DOS

DOS stands for Disk Operating System. In the early 1980s, Microsoft got the right

to QDOS (Quick and Dirty Operating System) developed by a small company,

Seattle Computer, and then has been sold it under the name MS-DOS. Microsoft

licenses a version called PC-DOS to IBM (International Business Machines) for its

IBM personal computers, and its version, MS-DOS, to many other PC

manufacturers.

Advantages and Disadvantages

Advantages: DOS has many advantages. The advantages will be the reasons for

learning DOS. DOS is the most popular microcomputer operating system for IBM

computers and compatibles ever sold worldwide. It runs thousands of applications, and is easy to use. DOS is easy for novices to use, and many

publications and books are available for the operating system. DOS runs on low-

priced IBM computers and compatibles. DOS does not require an expensive

computer system while some others still do.

Disadvantages: DOS has some drawbacks, but there is no doubt that we will

continue to see DOS used in the 1990s. It will then slowly be replaced as the

dominant operating system. The hardware has evolved in significant ways. New

microcomputers have more capacity and faster electronics than the old IBM PC

and compatibles. This makes DOS an old operating system.

DOS has direct access to only 640 kilobytes of primary storage, although new

microcomputers have much more primary storage. This restriction is an inherent

limitation of DOS. Today's new software for word processing, graphics,

spreadsheets, and database management requires more primary storage. In

addition, DOS is a single tasking operating system. It can support only one user



and one program at a time.

Another disadvantage is that DOS has a character-based interface. A graphical

user interface is easier to the users than the character-based interface.

File Access Table(FAT)

DOS creates a FAT for each disk during formatting. Every sector on the disk is

represented by an entry in the FAT as part of a cluster. DOS looks for available

clusters when a file is enlarged or created. When DOS allocates files on a freshly

formatted disk, DOS uses the first cluster and sequences through a connected

series of clusters, leaving many never-used clusters at the end of FAT. When a

file is erased or shortened, DOS marks the released clusters in the FAT asavailable again. When a file is allocated more than one cluster, each cluster

points to the next cluster that contains more of the files. The pointer is the next

cluster number. The result is a chain of clusters that comprise the map of a file's

disk storage. Thus, FAT acts as a storage map and tells DOS exactly where to go

on the disk to get all parts of a file.

How Application Programs Run in DOS

When the user specifies the application software to work on, the RAM part of

memory is filled with that image of that software. For example, if the user wants to

use WordPerfect, the command is taken from the command line and the

corresponding software is loaded on to the RAM and it works like a word

processor.

Files on DOS Disks

The files on DOS disks have specific purposes. A COM file extension identifies a

command file. Command files are the names of external DOS commands. Files

with CPI extensions operate the display screen. A file with the DAT extension is a

data file. Files with BAT extension are batch files. AUTOEXEC.BAT is a special

batch file that runs automatically when a computer is started. EXE files are

executable program files. SYS files are system files. SYS files are used to add or

modify hardware support to the basic PC operation.



Windows 3.x

This is a graphics-based operating environment from Microsoft. This operating

system runs under DOS. Thus, it is usually called "DOS with windows." Windows

3.x allows multiple tasking, allowing users to open several applications

simultaneously and shift between them. Windows operating system is very similar

to the Macintosh desktop environment.

Windows 3.x is a major upgrade of Microsoft's earlier versions. It provides a DOS

extender that allows Windows 3.x applications to run in up to 16MB of memory. In

the Windows, users can run DOS applications and change data between them.

Modes

Windows 3.x has three different operating modes.

Real Mode: This mode is for computers with less than 1MB of memory. It uses

expanded memory if available, and does not use extended memory.

Standard Mode: This is a normal Windows 3.0 operating mode. It works with

extended memory (XMS). This mode allows users to use DOS applications in the

window environment by allowing users to switch between DOS applications and

windows applications. The mode also uses expanded memory (EMS) if available.

386 Enhanced Mode: This mode is the extension of Windows/386 version that

runs on 386 and higher CPUs. This mode allows multitasking of Windows and

standard DOS applications. It converts character-based programs (DOS

applications) to bit-mapped graphics (Windows applications). It activates

EMM386.SYS memory manager to use EMS memory.


Advantages: Windows allows multitasking capability and more primary memory.

Windows provides a memory manager to allow users to access more than 640KB

of conventional memory. Another benefit of it is that it has a dynamic data

exchange function. Dynamic data exchange allows one program (e.g., a word



processing program) to request data or information from other programs (e.g., a

spreadsheet program or a database program etc.) currently running and use

those information. A graphical user interface (GUI) against character- based

approach is another advantage. This allows users to use Windows environment

such as mouse, pointer, clicking, icon, or pull-down menu.

Disadvantages: Windows 3.x can handle multitasking, but it is really switching

between tasks. Windows 3.x is not a multithreaded operating system. This works

well for many applications, but for some information and data can be lost if

Windows does not get back to a task soon enough. There are many application

programs for Windows, but users frequently demand more powerful application

programs that exceed the capabilities of current Windows programs. The other

disadvantage is that Windows 3.x was not originally intended for networks and is

not very efficient in that environment although it has a network version, Windows

for Workgroup 3.11.

Windows 95

Windows 95 upgrades its earlier versions (Windows 3.x) in many ways. It has a

new 3-D interface. It is mostly a 32- bit system although it has 16-bit components

included for compatibility with Windows 3.x. Windows 95 does not need to have a

separate DOS. It integrates all DOS services. A Windows 95 system runs in

protected mode. This means that it speeds up the processors and provides more

safety.

Windows 95 serves two purposes: It will move developers to the Win32 API and

will ease the transition for users whose hardware is not yet ready to handle the

demands of Windows NT.

Windows 95 offers better preemptive multitasking. Although for most things,

cooperative multitasking is good. However, if users want to do several things

simultaneously, they are going to find that preemptive multitasking provides

smoother operation and better speed.

Because Windows 95 is based on Win32 and has borrowed some of NT's

features, some people are confused over which Windows to use. Windows 95 is

for anyone who has a lower capability computer that does not enable to use



Windows NT. Windows 95 is likely to perform better than NT as a desktop

system, especially when running older 16-bit Windows applications.


Advantages: This operating system provides compatibility with existing Windows

and DOS programs. It also offers compatibility with existing Windows and DOS

device drivers. It works as in standalone computer and in networked environment

for both desktop and mobile users. It supports Windows for Workgroups, Novell

and UNIX-style networks.

It is easier to learn and use, gives users better performance, has more capacity,

integrates applications better, connects better, and crashes less than itspredecessor, Windows 3.x.

Disadvantages: Windows 95 still has limits from 16-bit components retained for

backward compatibility with 16-bit application. It does not give much benefit to the

16-bit applications. To get benefits from Windows 95, users must upgrade their

applications to 32-bit versions that support OLE and can interact directly with

Windows 95's shell. It will cost users significantly.

Difference of 95 with Windows NT

Windows 95 has a different user interface with Windows NT. The interface of NT

is much better. Windows 95 uses a different model for device drivers than NT.

Thus, not all Windows 95 applications run on NT without modification, and vice

versa. Windows 95 is a mix of 16- and 32-bit application programming interface,

but NT is solely a 32-bit interface.

Windows NT (New Technology)

Window NT is a platform for 32-bit Windows applications. This is a powerful and

one of the most advanced operating systems available today.

Windows NT was originally designed with big-system features. Beginning with

version 3.5, Microsoft began repositioning Windows NT as a workstation and

server operating system. It also has a sophisticated multiuser security system, so



Windows NT performs excellently as a disk server. NT has support for network

services useful to applications like client/server database engines. Still, all the

features of Windows NT are suitable for use in demanding applications of desktop

users.


Advantages: Windows NT allows users to run all applications, including Windows

applications, from the command line. It has better speed. Windows NT does not

have arbitrary resource limits. Computer system reliability is improved by the

result of this. It has the familiar Windows 3.x-style user interface, so users do not

need to spend much time for learning. NT has a preemptive multitaskingcapability, and the users can multitask applications within their own memory

spaces. It has much more reliable networking capability than that provided by

Windows 3.x or Windows 95.

Disadvantages: Windows NT is a platform for 32-bit Windows applications. 32- bit

applications are not widely available yet. Still, 16-bit applications are prevailing in

the software market. This operating system requires much resource. Windows NT

workstation requires 12MB of memory when run on Intel 486/pentium computers

(It runs in 8MB, but Microsoft recommends 12MB for NT to run adequately).

Windows NT server requires 16MB. Windows NT system that is run on an RISC

workstation also demands 16MB of memory. The NT requires at least 70MB of

hard disk space only for the operating system. After all, this operating system

requires too much for normal microcomputer users

OS/2

OS/2 stands for Operating System 2. This is another operating systems for

powerful microcomputers and networking. OS/2 was designed to avoid some of

the most serious limitations of DOS. OS/2 runs in 4MB of memory, although it

runs well in an 8MB system. It requires about 30MB of hard disk space. OS/2

WARP, the window version of OS/2, performs reasonably well in 4MB system and

requires less disk space.



Users do not need to abandon DOS and Windows to try out OS/2. OS/2 provides

a dual boot feature that allows users to boot up in either DOS or OS/2. OS/2 uses

folders much like those on the Macintosh and on some UNIX GUIs.


Advantages: It is not affected by requirements of DOS and Windows that certain

device drivers live in the first 640KB of memory. Instead, OS/2 can load network

adapter drivers, multimedia interfaces, CD-ROM software or video drivers into

memory as required. While OS/2 works very nicely with the same FAT file system

used by DOS, its HPFS has a number of benefits. It is significantly faster, it allows

a long file name, and it supports disk drivers as large as 256 gigabytes.This operating system allows multitasking and dynamic data interchange. It also

provides common graphical user interface with mainframes, minicomputers, and

microcomputers by OS/2 WARP. OS/2 was developed to assist in the sharing of

data and programs among several microcomputers. OS/2 solidly supports Novell

Netware and TCP/IP. Most network interface cards are supported.

Disadvantages: OS/2 Shell or WARP is similar to Windows, but is not identical. It

may take users a while to adjust to some of the differences. The application

programs developed specifically for OS/2 are not as many as those for Windows,

although more and more application developers are going to converting and

developing programs for OS/2 thesedays.

UNIX

UNIX was originally developed in 1969 by K. Thompson, R. Canaday and D.

Ritchie for minicomputers in the Bell Laboratories in the USA owned and run by

AT& T. By the mid-1970s, UNIX had been introduced to University of California at

Berkeley by Thompson, then widespread into an academic world. Most computer

science departments of universities have been used UNIX. UNIX initially became

popular in industry because for many years AT& T licensed the system to

universities for a nominal fee. The effect of this was that UNIX was carried by

recent computer science and engineering graduates to their new places of



employment. Rapid commercialization of UNIX followed on from this. This rapid

commercialization caused the lack of standards. Many hardware and software

vendors developed their own versions.

After UNIX was widespread, it had been used by scientists and engineers. It is

because of its scientific and technical orientation. It is less well known with

business people. All that, however, is probably about to change. The reason is

that with the arrival of very powerful microcomputers using the newer chips such

as pentium and pentium-pro chips, UNIX has become a major player in the

microcomputer world. The difficulty of learning is also about to change because of

the graphical user interface.

This is a multiuser, multitasking operating system that runs on many different

computer systems from microcomputer to mainframe, because UNIX is written in

C programming language, which is a language designed for system-level

programming. UNIX is consisted of a kernel, the file system, the user interface.

The kernel is the heart of the operating system. The file system has a hierarchical

directory method for organizing files on the disk and the shell.


Advantages: UNIX is the portable operating system that can be used with many

different computers from mainframe to microcomputer. The other operating

systems such as DOS, Windows, Mac operating system, and OS/2 cannot be

used for other systems. One of many strong features of UNIX is multitasking.

UNIX allows users to run multiple programs simultaneously.

UNIX also shares it among multiple users. UNIX is not restrained by the computer

systems such as conventional memory as the DOS and OS/2 systems are. It can

accomplish many operations that were formerly performed on minicomputers or

mainframes. It is important, because industry can achieve the performance and

benefits of large computers from microcomputers by using UNIX.

Networking is another strong feature of a UNIX operating system. UNIX can be

connected through several different kinds of equipment. It can share files among

them.



Disadvantages: Although UNIX can do many things, it can be difficult for novice

microcomputer users to understand. This is a reason it has had a limited impact

to date. UNIX was a minicomputer operating system used by programmers and

computer science professionals some time before the rise of the microcomputer.

This means that it has certain qualities making it useful to programmers - many

supporting utility programs and documentation, for instance. Some of its features

make it difficult for end users.

Limited application programs are another disadvantage for UNIX. UNIX off-the-

shelf programs for microcomputers are limited. However, this situation is going to

change, because many software vendors are rewriting DOS and Windows

applications for UNIX.

There is not a standard for UNIX. This may be the biggest problem for the

popularity of UNIX. The principal microcomputer versions are the AT& T UNIX

System V, the UC Berkeley UNIX, and Xenix developed by Microsoft for a

microcomputer version. AIX from IBM, Solaris, and Linux are other variants of

UNIX. An application program written for one version of UNIX may not run on

other versions.

There is also not a standard GUI for many UNIXs. There were several attempts to

combine the Sun, AT& T, and U.C. Berkeley versions of UNIX to produce a

standard graphical user interface. The one was Open Look (Sun/Open Windows)

by Sun, AT& T and Berkeley. Another graphical user interface was an OSF/Motif

by the Open Software Foundation (OSF). OSF/Motif is now in severe disarray.

Macintosh Operating Systems

It uses a graphics screen that places familiar office objects on a display screen.

Files, folders, programs, and disks are represented by icons. It has a hierarchical

file system that lets users drag document icons into and out of folder icons.

Folders can also contain other folders and so on.

In IBM computers and IBM compatible computers, software developers usually

decide how they make a user interface. In contrast, Macintosh application

developers usually conform to the Macintosh user interface. This consistent user

interface makes users easy to learn new programs from the start. This also



makes Macintosh operating system and its application programs

indistinguishable.

The Macintosh user interface style has been adapted to many other operating

systems. For example, OS/2 Presentation Manager and WARP, New Wave, most

UNIX systems, and Windows look very similar to the Macintosh graphics user

interface.

The Macintosh operating system has two major files. They are the System file

and the Finder. The system file manages the user interface. Both files work

together to achieve the operating system procedures such as formatting disks,

copying files, erasing files, and running application programs.


Advantages: The ease of use is the primary charm of the Macintosh. The

graphics interface such as menus, screen display, and dialog boxes are quite

more consistent across applications than they are in Windows. It also offers easy

plug and play. When install a board in a Mac, users need to plug it into a slot,

drag its driver icon into the System Folder, and reboot the computer.

It provides long filenames, integrated program and file management, desktop

icons, and shortcuts. It provides a high quality graphics processing that makes

Macintosh popular for desktop publishing (Mac is the standard computer in the

publishing industry). It has a great video architecture that allows users to add

multiple monitors to a computer by adding another video board and hook up

another monitor.

The later versions of Macintosh operating system (System 7.x series) enable

users to do multitasking. That is, multiple programs can run simultaneously, each

sharing the CPU (cooperative multitasking like Windows 3.x). System 7.x allows

applications programs to exchange and share data and commands with other

application programs.

It even provides built-in sound, SCSI, and Ethernet that allow users to work easily

with multimedia. It has much better multimedia toolkit than Windows has. The IBM

and compatible computers, PC, cannot match the Macintosh's toolkits for

multimedia, and Windows multimedia applications do not work together as

smoothly as their Macintosh counterparts.



Disadvantages: The first disadvantage of the Macintosh platform is the

incompatibility with DOS and Windows (PC) applications. This has been made

Macintoshes less attractive to corporate users that want to have compatibility and

connectivity within company and between companies. However, software (e.g.,

Insignia's SoftWindows) are now available for the Mac to allow it to run Windows

on PowerMac although it runs slowly. This is a great utility for a Mac user who

needs to run DOS or Windows applications occasionally. Another solution for this

is the fact that networks connecting Macintoshes to PCs are available these days.

Types of Utilities

A utility program, also called a utility, is a type of system software that allows auser to perform maintenance-type tasks, usually related to managing a compter,

its devices, or its programs. Most operating systems include several built-in utility

programs. Users often buy stand-alone utilities, however, because they offer

improvements over those included with the operating system. There are few

types of utilities recently used:

Antivirus Programs

The term, computer virus, describes a potentially damaging computer program

that affects, or infects, a computer negatively by altering the way the computer

works without the user’s knowledge or permission. Once the virus is in a

computer, it can spread throughout and may damage your files and operating

system. To protect a computer from virus attacks, users should install an antiirus

program and update it frequently. An antivirus program protects a computer

against viruses by identifying and removing any computer viruses found in

memory, on storage media, or on incoming files. Most antivirus programs also

protect against worms and Trojan Horses. When you puchase a new computer, it

often includes antivirus software.

Spyware and Adware Removers

Spyware is a program placed on a computer without the user’s knowledge that

secretly collects information about the user, often related to Web browsing

habits. The spyware program communicates information it collects to some



outside source while you are online. Adware is a program that displays an online

advertisement in a banner or pop-up window on Web pages, e-mail, or other

Internet services. Sometimes, spyware is hidden in adware.

Disc Burning

Disc burning software writes text, graphics, audio, and video files on a recordable

or rewritable CD, DVD, or Blu-ray Disc. This software enables the home user

easily to back up contents of their hard disk on an optical disc and make

duplicates of uncopyrighted music or movies. Disc burning software usually also

include photo editing, audio editing, and video editing capabilities.

Media Player

A media player is a program that allows you to view images and animation, listen

to audio, and watch video files on your computer. Media players may also include

the capability to organize media files, convert them to different formats, connect

to and purchase media from an online media store, download podcasts and

vodcasts, burn audio CDs, and transfer media to portable media players.

Windows includes Windows Media Player.



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References

http://www.jegsworks.com/Lessons/lesson8/lesson8-3.htm

http://www.elawexchange.com/index.php?

option=com_content&view=article&id=169&Itemid=235

http://spamlaws.com/operating-system-function.html

http://en.wikipedia.org/wiki/Category:Operating_systems

http://www.sun.com/software/solaris/features.jsp

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