Showing posts with label HISTORY OF COMPUTERS. Show all posts
Showing posts with label HISTORY OF COMPUTERS. Show all posts

Sunday, 25 January 2015

Types of Computer

On the basis of working principle there are three types of computers.

a)Analog Computer
An analog computer (spelt analogue in British English) is a form of computer that uses continuous
physical phenomena such as electrical, mechanical or hydraulic quantities to model the problem being solved.
1. Thermometer
2. Speedometer
3. Petrol Pump Indicator
4. Multi meter

b) Digital Computer
Acomputer that performs calculations and logical operations with quantities represented as digits, usually in the binary number system.

c) Hybrid Computer (Analog + Digital)
A combination of computers those are capable of inputting and outputting in both digital and analog
signals. A hybrid computer system setup offers a cost effective method of performing complex simulations.

On the basis of Size..
a)Super Computer 
It is the fastest computer. Supercomputers are very expensive and are employed for specialized applications that require immense amounts of mathematical calculations.
For example, weather forecasting requires a supercomputer. Other uses of supercomputers
include animated graphics, fluid dynamic calculations and nuclear energy research and petroleum
The major difference between a supercomputer and a mainframe is that a supercomputer channels
all its power into executing a few programs as fast as possible, whereas a mainframe uses itspower to execute many programs concurrently.

b)Mainframe Computer
A very large and expensive computer capable of supporting hundreds and even thousands of users
simultaneously. In the hierarchy that starts with a simple microprocessor (Eg: in watches) at the
bottom and moves to supercomputers at the top, mainframes are just below supercomputers. In
some ways, mainframes are more powerful than supercomputers because they support more simultaneous programs. But supercomputers can execute a single program
faster than a mainframe.

c) Mini Computer
In size and power, minicomputers lie between workstations and mainframes. In the past decade, the distinction between large minicomputers and small mainframes has blurred, however, as has the
distinction between small minicomputers and workstations. But in general, a minicomputer is a
multiprocessing system capable of supporting from 4 to about 200
users simultaneously.

d)Micro Computer
i. Desktop Computer: A personal or micro-mini computer sufficient to fit on a desk.
ii. Laptop Computer: A portable computer complete with an integrated screen and keyboard. It is
generally smaller in size than a desktop computer and larger than
a notebook computer.
iii. Palmtop Computer/ Digital Diary/ Notebook / PDAs:Ahandsized computer. Palmtops have no keyboard but the screen serves both as an input and output device.

It is a terminal or desktop computer in a network. In this context, workstation is just a generic term
for a user's machine (client machine) in contrast to a "server" or "mainframe."

Major brands of the computer:
a) IBM/ IBM Compatible Computers
b) Apple/ Macintosh.

Monday, 16 July 2012


Generation of Computers
It is important to realize that major changes and trends in computer systems have occurred during the major  stages-or generations-of computing, and will continue into the future. The first generation of computers developed in the early 1950s, the second generation blossomed during the late 1960s, the third generation took computing into the 1970s, and the fourth generation has been the computer technology of the 1980s and 1990s. A fifth generation of computers that accelerates the trends of the previous generations is expected to evolve as we enter the 21st century. Notice that computers continue to become smaller, faster, more reliable, less costly to purchase and maintain, and more interconnected within computer networks.
First-generation computing involved massive computers using hundreds or thousands of vacuum tubes for their processing and memory circuitry. These large computers generated enormous amounts of heat; their vacuum tubes had to be replaced frequently. Thus, they had large electrical power, air conditioning, and maintenance requirements. First-generation computers had main memories of only a few thousand characters and millisecond processing speeds. They used magnetic drums or tape for secondary storage and punched cards or paper tape as input and output media.
Second-generation computing used transistors and other solid-state, semiconductor devices that were wired to circuit boards in the computers. Transistorized circuits were much smaller and much more reliable, generated little heat, were less expensive, and required less power than vacuum tubes. Tiny magnetic cores were used for the computer’s memory, or internal storage. Many second-generation computers had main memory capacities of less than 100 kilobytes and microsecond processing, speeds. Removable magnetic disk packs were introduced, and magnetic tape merged as the major input, output, and secondary storage medium for large computer installations.

Wednesday, 2 November 2011


access time - The performance of a hard drive or other storage device - how long it takes to locate a file.
active program or window - The application or window at the front (foreground) on the monitor.
alert (alert box) - a message that appears on screen, usually to tell you something went wrong.
alias - an icon that points to a file, folder or application (System 7).
apple menu - on the left side of the screen header. System 6 = desk accessories System 7 = up to 50 items.
application - a program in which you do your work.
application menu - on the right side of the screen header. Lists running applications.
ASCII (pronounced ask-key ) - American Standard Code for Information Interchange. a commonly used data format for exchanging information between computers or programs.
background - part of the multitasking capability. A program can run and perform tasks in the background while another program is being used in the foreground.
bit - the smallest piece of information used by the computer. Derived from "binary digit". In computer language, either a one (1) or a zero (0).
backup - a copy of a file or disk you make for archiving purposes.
boot - to start up a computer.
bug - a programming error that causes a program to behave in an unexpected way.
bus - an electronic pathway through which data is transmitted between components in a computer.
byte - a piece of computer information made up of eight bits.
card - a printed circuit board that adds some feature to a computer.
cartridge drive - a storage device, like a hard drive, in which the medium is a cartridge that can be removed.
CD-ROM - an acronym for Compact Disc Read-Only Memory.
Chooser - A desk accessory used to select a printer, or other external device, or to log onto a network.
Clipboard - A portion of memory where the Mac temporarily stores information. Called a Copy Buffer in many PC applications because it is used to hold information which is to be moved, as in word processing where text is "cut" and then "pasted".
Clock Rate (MHz) - The instruction processing speed of a computer measured in millions of cycles per second (i.e., 200 MHz).
command - the act of giving an instruction to your Mac either by menu choice or keystroke.
command (apple) key - a modifier key, the Command key used in conjunction with another keystroke to active some function on the Mac.
compiler - a program the converts programming code into a form that can be used by a computer.
compression - a technique that reduces the size of a saved file by elimination or encoding redundancies (i.e., JPEG, MPEG, LZW, etc.)
control key - seldom used modifier key on the Mac.
control panel - a program that allows you to change settings in a program or change the way a Mac looks and/or behaves.
CPU - the Central Processing Unit. The processing chip that is the "brains" of a computer.
crash - a system malfunction in which the computer stops working and has to be restarted.
cursor - The pointer, usually arrow or cross shaped, which is controlled by the mouse.
daisy chaining - the act of stringing devices together in a series (such as SCSI).
database - an electronic list of information that can be sorted and/or searched.
data - (the plural of datum) information processed by a computer.
defragment - (also - optimize) to concatenate fragments of data into contiguous blocks in memory or on a hard drive.
desktop - 1. the finder. 2. the shaded or colored backdrop of the screen.
desktop file - an invisible file in which the Finder stores a database of information about files and icons.
dialog box - an on-screen message box that appears when the Mac requires additional information before completing a command.
digitize - to convert linear, or analog, data into digital data which can be used by the computer.
disk - a spinning platter made of magnetic or optically etched material on which data can be stored.
disk drive - the machinery that writes the data from a disk and/or writes data to a disk.
disk window - the window that displays the contents or directory of a disk.
document - a file you create, as opposed to the application which created it.
DOS - acronym for Disk Operating System - used in IBM PCs.
DPI - acronym for Dots Per Inch - a gauge of visual clarity on the printed page or on the computer screen.
download - to transfer data from one computer to another. (If you are on the receiving end, you are downloading. If you are on the sending end, you are uploading ).
drag - to move the mouse while its button is being depressed.
drag and drop - a feature on the Mac which allows one to drag the icon for a document on top of the icon for an application, thereby launching the application and opening the document.
driver - a file on a computer which tells it how to communicate with an add-on piece of equipment (like a printer).
Ethernet - a protocol for fast communication and file transfer across a network.
expansion slot - a connector inside the computer which allows one to plug in a printed circuit board that provides new or enhanced features.
extension - a startup program that runs when you start the Mac and then enhances its function.
fibre channel - as applied to data storage and network topology
file - the generic word for an application, document, control panel or other computer data.
finder - The cornerstone or home-base application in the Mac environment. The finder regulates the file management functions of the Mac (copying, renaming, deleting...)
floppy - a 3.5 inch square rigid disk which holds data. (so named for the earlier 5.25 and 8 inch disks that were flexible).
folder - an electronic subdirectory which contains files.
font - a typeface that contains the characters of an alphabet or some other letterforms.
footprint - The surface area of a desk or table which is occupied by a piece of equipment.
fragmentation - The breaking up of a file into many separate locations in memory or on a disk.
freeze - a system error which causes the cursor to lock in place.
get info - a Finder File menu command that presents an information window for a selected file icon.
gig - a gigabyte = 1024 megabytes.
hard drive - a large capacity storage device made of multiple disks housed in a rigid case.
head crash - a hard disk crash caused by the heads coming in contact with the spinning disk(s).
high density disk - a 1.4 MB floppy disk.
highlight - to select by clicking once on an icon or by highlighting text in a document.
icon - a graphic symbol for an application, file or folder.
initialize - to format a disk for use in the computer; creates a new directory and arranges the tracks for the recording of data.
insertion point - in word processing, the short flashing marker which indicates where your next typing will begin.
installer - software used to install a program on your hard drive.
interrupt button - a tool used by programmers to enter the debugging mode. The button is usually next to the reset button.
K - short for kilobyte.
keyboard shortcut - a combination of keystrokes that performs some function otherwise found in a pulldown menu.
kilobyte - 1024 bytes.
landscape - in printing from a computer, to print sideways on the page.
launch - start an application.
Measurements (summary) -
*a bit = one binary digit (1 or 0) *"bit" is derived from the contraction b'it (binary digit) -> 8 bits = one byte
*1024 bytes = one kilobyte
*K = kilobyte
*Kb = kilobit
*MB = megabyte
*Mb = megabit
*MB/s = megabytes per second
*Mb/s = megabits per second
*bps = bits per second
i.e., 155 Mb/s = 19.38 MB/s

MB - short for megabyte.
megabyte - 1024 kilobytes.
memory - the temporary holding area where data is stored while it is being used or changed; the amount of RAM a computer has installed.
menu - a list of program commands listed by topic.
menu bar - the horizontal bar across the top of the Mac¹s screen that lists the menus.
multi finder - a component of System 6 that allows the Mac to multi task.
multi tasking - running more than one application in memory at the same time.
nanosecond - one billionth of a second. ( or, the time between the theatrical release of a Dudley Moore film and the moment it begins to play on airplanes).
native mode - using the computers original operating system; most commonly used when talking about the PowerPC can run software written for either the 80x0 systems, or the PowerPC¹s RISC code.
NuBus - expansion slots on the Mac which accept intelligent, self-configuring boards. NuBus is a different bus achitecture than the newer PCI bus and the boards are not interchangable.
operating system - the system software that controls the computer.
optical disk - a high-capacity storage medium that is read by a laser light.
palette - a small floating window that contains tools used in a given application.
partition - a subdivision of a hard drives surface that is defined and used as a separate drive.
paste - to insert text, or other material, from the clipboard or copy buffer.
PC - acronym for personal computer, commonly used to refer to an IBM or IBM clone computer which uses DOS.
PCI - acronym for Peripheral Component Interchange - the newer, faster bus achitecture.
peripheral - an add-on component to your computer.
point - (1/72") 12 points = one pica in printing.
pop-up menu - any menu that does not appear at the top of the screen in the menu bar. (may pop up or down)
port - a connection socket, or jack on the Mac.
Power PC - a processing chip designed by Apple, IBM and Motorola (RISC based).
Power Mac - a family of Macs built around the PowerPC chip.
print spooler - a program that stores documents to be printed on the hard drive, thereby freeing the memory up and allowing other functions to be performed while printing goes on in the background.
QuickTime - the Apple system extension that gives one the ability to compress, edit and play animation, movies and sound on the Mac.
RAM - acronym for Random-Access Memory.
reset switch - a switch on the Mac that restarts the computer in the event of a crash or freeze.
resize box - the small square at the lower right corner of a window which, when dragged, resizes the window.
RISC - acronym for Reduced Instruction Set Computing; the smaller set of commands used by the PowerPC and Power Mac.
ROM - acronym for Read Only Memory; memory that can only be read from and not written to.
root directory - the main hard drive window.
save - to write a file onto a disk.
save as - (a File menu item) to save a previously saved file in a new location and/or with a new name.
scroll - to shift the contents of a window to bring hidden items into view.
scroll bar - a bar at the bottom or right side of a window that contains the scroll box and allows scrolling.
scroll box - the box in a scroll bar that is used to navigate through a window.
SCSI - acronym for Small Computer System Interface.
SCSI address - a number between zero and seven that must be unique to each device in a SCSI chain. Fast and Wide SCSI devices will allow up to 15 SCSI Ids (hexidecimal); however, the length restriction (3 meters) is such that it is virtually impossible to link 15 devices together.
SCSI port - a 25 pin connector on the back of a Mac (native SCSI port); used to connect SCSI devices to the CPU. Some SCSI cards (like the ATTO) have a 68 pin connector.
SCSI terminator - a device placed at the end of a SCSI chain to complete the circuit. (some SCSI devices are self-terminating, or have active termination and do not require this plug).
serial port - a port that allows data to be transmitted in a series (one after the other), such as the printer and modem ports on a Mac.
server - a central computer dedicated to sending and receiving data from other computers (on a network).
shut down - the command from the Special menu that shuts down the Mac safely.
software - files on disk that contain instructions for a computer.
spreadsheet - a program designed to look like an electronic ledger.
start up disk - the disk containing system software and is designated to be used to start the computer.
surge suppressor - a power strip that has circuits designed to reduce the effects of surge in electrical power. (not the same as a UPS)
System file - a file in the System folder that allows your Mac to start and run.
System folder - an all-important folder that contains at least the System file and the Finder.
32 bit addressing - a feature that allows the Mac to recognize and use more than 8MB of memory.
title bar - the horizontal bar at the top of a window which has the name of the file or folder it represents.
upload - to send a file from one computer to another through a network.
Uninterruptible Power Source (UPS)- a constantly charging battery pack which powers the computer. A UPS should have enough charge to power your computer for several minutes in the event of a total power failure, giving you time to save your work and safely shut down.
UPS - acronym for Uninterruptible Power Source.
vaporware - "software" advertised, and sometimes sold, that does not yet exist in a releasable for.
virtual memory - using part of your hard drive as though it were "RAM".
WORM - acronym for Write Once-Read Many; an optical disk that can only be written to once (like a CD-ROM).
zoom box - a small square in the upper right corner of a window which, when clicked, will expand the window to fill the whole screen.


The concept of data communication  - transmitting data between two different places, connected via some kind of electromagnetic medium, such as radio or an electrical wire - actually predates the introduction of the first computers. Such communication systems were typically limited to point to point communication between two end devices. Telegraph systems and telex machines  can be considered early precursors of this kind of communication. The earlier computers used the technology available at the time to allow communication between the central processing unit and remote terminals. As the technology evolved new systems were devised to allow communication over longer distances (for terminals) or with higher speed (for interconnection of local devices) that were necessary for the mainframe computer  model. Using these technologies it was possible to exchange data (such as files) between remote computers. However, the point to point communication model was limited, as it did not allow for direct communication between any two arbitrary systems; a physical link was necessary. The technology was also deemed as inherently unsafe for strategic and military use, because there were no alternative paths for the communication in case of an enemy attack.
As a response, several research programs started to explore and articulate principles of communications between physically separate systems, leading to the development of the packet switching model of digital networking. These research efforts included those of the laboratories of Vinton G. Cerf at Stanford University, Donald Davies (NPL), Paul Baran (RAND Corporation), and Leonard Kleinrock at MIT and at UCLA. The research led to the development of several packet-switched networking solutions in the late 1960s and 1970s, including ARPANET, Telenet, and the X.25 protocols. Additionally, public access and hobbyist networking systems grew in popularity, including unix-to-unix copy (UUCP) and FidoNet. They were however still disjointed separate networks, served only by limited gateways between networks. This led to the application of packet switching to develop a protocol for internetworking, where multiple different networks could be joined together into a super-framework of networks. By defining a simple common network system, the Internet Protocol Suite, the concept of the network could be separated from its physical implementation. This spread of internetworking began to form into the idea of a global network that would be called the Internet, based on standardized protocols officially implemented in 1982. Adoption and interconnection occurred quickly across the advanced telecommunication networks of the western world, and then began to penetrate into the rest of the world as it became the de-facto international standard for the global network. However, the disparity of growth between advanced nations and the third-world countries led to a digital divide that is still a concern today.
Following commercialization and introduction of privately run Internet service providers in the 1980s, and the Internet's expansion for popular use in the 1990s, the Internet has had a drastic impact on culture and commerce. This includes the rise of near instant communication by electronic mail (e-mail), text based discussion forums, and the World Wide Web. Investor speculation in new markets provided by these innovations would also lead to the inflation and subsequent collapse of the Dot-com bubble. But despite this, the Internet continues to grow, driven by commerce, greater amounts of online information and knowledge and social networking known as Web 2.0.

General Search Engines
Alexa Web Search: analyzes site traffic including ranking, global users, pages linking to the site, and links to related pages of interest
AllTheWeb : returns results quickly from a database gathered by the Yahoo! crawler; offers multimedia and news searches; has a good advanced search interface
AltaVista : searches Web sites with advanced Boolean and field search options. See also Babel Fish, the AltaVista translation service. : general search engine enhanced by a number of specialty searches including a dictionary, thesaurus, currency converter, encyclopedia, maps, news and more
Bing : Microsoft engine that displays excerpts from sites retrieved by your search and offers related search suggestions; multimedia and other deep Web results are also displayed. Bing focuses on searches related to making a purchase decision, planning a trip, researching a health condition, and finding a local business. Also check out Bing Maps Beta.
ChaCha : search engine that offers live human guides to help answer queries; focuses on questions from mobile devices
Exalead : offers concept clustering of results, thumbnail images of retrieved sites, and customization options such as organization of results by file type, geography or modification date
Factbites : searches for full topic matches and returns meaningful, full sentence excerpts of sites in its results list
Google : Web's most popular search engine that retrieves results in real time as you type your search. Also check out Eco Smart, a Google-powered search engine with a black background display that saves energy.
Hakia : organizes results into types of information sources, including "credible " sites recommended by librarians
iSEEK Education : offers authoritative resources from university, government, and established noncommercial providers; organizes results into concept clusters, and also allows users to recommend and rate sites
Lycos : general search engine that also offers searches of a few deep Web content sources including people look-up, yellow pages, and multimedia
Quintura : displays a type of tag cloud with keywords related to your search that can be selected to generate new results
Search : service that limits results to the .edu, domain; also offers to search well-known dictionaries, encyclopedias, almanacs, etc.
Snappy Fingers : searches millions of Frequently Asked Questions (FAQs) for answers to user queries
Sproose : searches Yahoo! and allows users to comment on and vote on its search results
Webbrain : offers results in visual layout of related terms for subsequent searching
Wolfram Alpha : enter a question or calculation, and Wolfram Alpha uses its built-in algorithms and own collection of data to compute the answer
Yahoo : portal with a general Web search and many other content services.

Computer Virus

A computer virus is a computer program that can copy itself and infect a computer. The term "virus" is also commonly but erroneously used to refer to other types of malware, including but not limited to adware and spyware  programs that do not have the reproductive ability. A true virus can spread from one computer to another (in some form of executable code) when its host is taken to the target computer; for instance because a user sent it over a network or the Internet, or carried it on a removable medium such as a floppy disk, CD, DVD, or USB drive.
Viruses can increase their chances of spreading to other computers by infecting files on a network file system or a file system that is accessed by another computer.
As stated above, the term "computer virus" is sometimes used as a catch-all phrase to include all types of malware, even those that do not have the reproductive ability. Malware includes computer viruses, computer worms, Trojan horses, most rootkits, spyware, dishonest adware and other malicious and unwanted software, including true viruses. Viruses are sometimes confused with worms and Trojan horses, which are technically different. A worm can exploit security vulnerabilities to spread itself automatically to other computers through networks, while a Trojan horse is a program that appears harmless but hides malicious functions. Worms and Trojan horses, like viruses, may harm a computer system's data or performance. Some viruses and other malware have symptoms noticeable to the computer user, but many are surreptitious or simply do nothing to call attention to themselves. Some viruses do nothing beyond reproducing themselves.
Recovery methods:
Once a computer has been compromised by a virus, it is usually unsafe to continue using the same computer without completely reinstalling the operating system. However, there are a number of recovery options that exist after a computer has a virus. These actions depend on severity of the type of virus.


Microsoft Office is an office suite of inter-related desktop applications, servers and services for the Microsoft Windows and Mac OS X  operating systems, introduced by Microsoft in 1989. Initially a marketing term for a bundled set of applications, the first version of Office contained Microsoft Word, Microsoft Excel, and Microsoft PowerPoint. Additionally, a "Pro" (Professional) version of Office included Microsoft Access and Schedule Plus. Over the years, Office applications have grown substantially closer with shared features such as a common spell checker, OLE data integration and Microsoft Visual Basic for Applications scripting language. Microsoft also positions Office as a development platform for line-of-business software under the Office Business Applications (OBA) brand.
The current versions are Office 2010 for Windows which was released on June 15, 2010, and Office 2011 for Mac OS X, released October 26, 2010. Office 2007 and 2008 introduced a new user interface and new Office Open XML document formats (docx, xlsx, pptx). Consequently, Microsoft has made available, free of charge, an add-on known as the Microsoft Office Compatibility Pack to allow Office 2000-2003 for Windows and Office 2004 for Mac editions to open, edit, and save documents created under the new formats for Office 2007.

Microsoft Word:
Microsoft Word is a word processor and was previously considered to be the main program in Office. Its proprietary DOC format is considered a de facto standard, although Word 2007 can also use a new XML-based, Microsoft Office-optimized format called .DOCX which has been standardized by Ecma International as Office Open XML and its SP2 update will support ODF and PDF. Word is also available in some editions of Microsoft Works. It is available for the Windows and Mac platforms. The first version of Word, released in the autumn of 1983, was for the MS-DOS operating system and had the distinction of introducing the mouse to a broad population. Word 1.0 could be purchased with a bundled mouse, though none was required. Following the precedents of LisaWrite and MacWrite, Word for Macintosh attempted to add closer WYSIWYG features into its package. Word for Mac was released in 1985. Word for Mac was the first graphical version of Microsoft Word. Despite its bugginess, It became one of the most popular Mac applications.
Microsoft Excel:
Microsoft Excel is a spreadsheet program which originally competed with the dominant Lotus 1-2-3, but eventually outsold it. It is available for the Windows and Mac platforms. Microsoft released the first version of Excel for the Mac in 1985, and the first Windows version (numbered 2.05 to line up with the Mac and bundled with a standalone Windows run-time environment) in November 1987.
Microsoft Outlook and Microsoft Entourage:
Microsoft Outlook (not to be confused with Outlook Express) is a personal information manager and e-mail communication software. The replacement for Windows Messaging, Microsoft Mail and Schedule+ starting in Office 97, it includes an e-mail client, calendar, task manager and address book. Office Although historically it has been offered for the Mac, the closest to an equivalent for Mac OS X is Microsoft Entourage, which offers a slightly different feature set. Office 2011 for Mac will reintroduce Outlook, replacing Entourage.
Microsoft PowerPoint:
Microsoft PowerPoint is a popular presentation program for Windows and Mac. It is used to create slideshows, composed of text, graphics, movies and other objects, which can be displayed on-screen and navigated through by the presenter or printed out on transparencies or slides. This is convenient for school or work presentations. Office Mobile for Windows Mobile 5.0 and later features a version of PowerPoint called PowerPoint Mobile. Movies, videos, sounds and music, as well as Wordart and Autoshapes can be added to slideshows.
Microsoft Publisher:
Microsoft Publisher is a program mostly used for designing brochures, labels, calendars, greeting cards, business cards, newsletters, and postcards.

History of Microsoft Windows

Microsoft began to develop the Windows graphical user interface program in 1983. The goal was to provide a more user-friendly program that worked within the MS-DOS operating system on IBM PCs. Over the course of time, a number of further developments came with each successive generation. By the early 21st century, Microsoft Windows became the most popular operating system in the world.
Version 1.0:
On November 20, 1985 the first version of Microsoft Windows was released. It worked as an operating environment within MS-DOS and featured a number of programs including a word processor, calendar and painting option.
Version 3.0:
Although a number of changes and modifications occurred in the interim, the next major success for Microsoft Windows was version 3.0, released in 1990. It offered increased virtual memory, which allowed users to multitask much easier.
Windows 95:
Windows 95 was released in 1995 by Microsoft in an effort to integrate new 32-bit programming capabilities. This version was the first to include Internet Explorer, the company's preferred Internet access program.
Windows 2000:
In 2000, Microsoft released its next Windows operating system. This version improved on the device manager program, Windows Media Player and DirectX. It was able to work on both servers and standard workstations.
Windows XP:
The following year, Windows XP was released. This version was troubled from the start with security problems, leading to a number of modifications that had to be sent out over the Internet or with specialized disks.
Windows Vista:
Windows Vista became the next generation operating system in 2007. Microsoft launched a number of different versions, each with its own features. The overall goal of the system was to offer better security as well as improved graphics.
Windows 7:
Windows 7 is the latest release of Microsoft Windows, a series of operating systems produced by Microsoft for use on personal computers, including home and business desktops, laptops, netbooks, tablet PCs, and media center PCs. Windows 7 was released to manufacturing on July 22, 2009, and reached general retail availability on October 22, 2009, less than three years after the release of its predecessor, Windows Vista. Windows 7's server counterpart, Windows Server 2008 R2, was released at the same time.
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 which Windows Vista was not at the time. Presentations given by Microsoft in 2008 focused on multi-touch support, a redesigned Windows shell with a new taskbar, referred to as the Superbar, a home networking system called HomeGroup, and performance improvements. Some standard applications that have been included with prior releases of Microsoft Windows, including Windows Calendar, Windows Mail, Windows Movie Maker, and Windows Photo Gallery, are not included in Windows 7; most are instead offered separately at no charge as part of the Windows Live Essentials suite.


Generation of  Computers
It is important to realize that major changes and trends in computer systems have occurred during the major  stages-or generations-of computing, and will continue into the future. The first generation of computers developed in the early 1950s, the second generation blossomed during the late 1960s, the third generation took computing into the 1970s, and the fourth generation has been the computer technology of the 1980s and 1990s. A fifth generation of computers that accelerates the trends of the previous generations is expected to evolve as we enter the 21st century. Notice that computers continue to become smaller, faster, more reliable, less costly to purchase and maintain, and more interconnected within computer networks.
First-generation computing involved massive computers using hundreds or thousands of vacuum tubes for their processing and memory circuitry. These large computers generated enormous amounts of heat; their vacuum tubes had to be replaced frequently. Thus, they had large electrical power, air conditioning, and maintenance requirements. First-generation computers had main memories of only a few thousand characters and millisecond processing speeds. They used magnetic drums or tape for secondary storage and punched cards or paper tape as input and output media.
Second-generation computing used transistors and other solid-state, semiconductor devices that were wired to circuit boards in the computers. Transistorized circuits were much smaller and much more reliable, generated little heat, were less expensive, and required less power than vacuum tubes. Tiny magnetic cores were used for the computer’s memory, or internal storage. Many second-generation computers had main memory capacities of less than 100 kilobytes and microsecond processing, speeds. Removable magnetic disk packs were introduced, and magnetic tape merged as the major input, output, and secondary storage medium for large computer installations.
Third-generation computing saw the development of computers that used integrated circuits, in which thousands of transistors and other circuit elements are etched on tiny chips of silicon. Main memory capacities increased to several megabytes and processing speeds jumped to millions of instructions per second (MIPS) as telecommunications capabilities became common. This made it possible for operating system programs to come into widespread use that automated and supervised the activities of many types of peripheral devices and processing by mainframe computers of several programs at the same time, frequently involving networks of users at remote terminals. Integrated circuit technology also made possible the development and widespread use of small computers called minicomputers in the third computer generation.
Fourth-generation computing relies on the use of LSI (large-scale integration) and VLSI (very-large-scale integration) technologies that cram hundreds of thousands or millions of transistors and other circuit elements on each chip. This enabled the development of microprocessors, in which all of the circuits of a CPU are contained on a single chip with processing speeds of millions of instructions per second. Main memory capacities ranging from a few megabytes to several gigabytes can also be achieved by memory chips that replaced  magnetic core memories. Microcomputers, which use microprocessor CPUs and a variety of peripheral devices and easy-to-use software packages to form small personal computer (PC), systems or client/server networks of linked PCs and servers, are a hallmark of the fourth generation of computing, which accelerated the downsizing of computing systems.
Whether we are moving into a fifth generation of computing is a subject of debated since the concept of generations may no longer fit the continual, rapid changes occurring in computer hardware, software, data, and networking technologies. But in any case, we can be sure that progress in computing will continue to accelerate, and that the development of Internet-based technologies and applications will be one of the major forces driving computing into the 21st century.

Computer System  Concepts and Components

The Computer System Concept:
A computer is more than a high-powered collection of electronic devices performing a variety of information processing chores. A computer is a system, an interrelated combination of components that performs the basic system functions of input, processing, output, storage, and control, thus providing end users with a powerful information processing tool. Understanding the computer as a computer system is vital to the effective use and management of computers.
A computer is system of hardware devices organized according to the following system functions.
The input devices of a computer system include keyboards, touch screens, pens, electronic mice, optical scanners, and so on.
 The central processing unit( CPU) is the main processing component of a computer system. (In microcomputers, it is the main microprocessor.) In particular, the electronic circuits of the arithmetic-logic unit one of the CPU’s major components, perform the arithmetic and logic functions required in computer processing.
 The output devices of a computer system include video display units, printers, audio response units , and so on, They convert electronic information produced by the computer system into human intelligible form for presentation to end users.
 The storage function of a computer system takes place in the storage circuits of the computer’s primary storage unit, or memory, and in secondary storage devices such as magnetic disk and tape units. These devices store data and program instructions needed for processing.
 The control unit of the CPU is the control component of a computer system. Its circuits interpret computer program instructions and transmit directions to the other components of the computer system.
Central Processing Unit:
The central processing unit is the most important hardware component of a computer system. It is also known as the CPU, the central processor or instruction processor, and the main microprocessor in a microcomputer. Conceptually, the circuitry of a CPU can be subdivided into two major subunits the arithmetic-logic unit and the control unit. The CPU also includes circuitry for devices such as registers and cache memory for high speed, temporary storage of instruction  operations, input/output, and telecommunications support.
The control unit obtains instructions from software segments stored in the primary storage unit and interprets them. Then it transmits electronic signals to the other components of the computer system to perform required operations. The arithmetic-logic unit performs required arithmetic and comparison operations .A computer can make logical changes from one set of program instructions to another (e.g, overtime pay versus regular pay calculations) based on the results of comparisons made in the ALU during processing.
Main Memory and Primary Storage Unit:
A computer’s primary storage unit is commonly called main memory, and holds data and program instructions between processing steps and supplies them to the control unit and arithmetic-logic unit during processing. Most of a computer’s memory consists of microelectronic semiconductor memory chips known as RAM (random access memory ). The contents of these memory chips can be instantly changed to store new data. Other, more permanent memory chips called ROM (read only memory) may also be used.
Secondary storage devices like magnetic disks and optical disks are used to store data and programs and thus greatly enlarge the storage capacities of computer system. Also, since memory circuits typically lose their contents when electric power is turned off, most secondary storage media provide a more permanent type of storage. However the contents of hard disk drives floppy disks, CD-ROM disks, and other secondary storage media cannot be processed without first being brought into memory. Thus secondary storage devices play a supporting role to the primary storage of a computer system.
Multiple Processors:
Many current computers, from microcomputers to large mainframes, use multiple processors for their processing functions. Instead of having one CPU with a single control unit and arithmetic-logic unit, the CPUs of these computers contain several type of processing units. Let’s briefly look at the major types of such multiprocessor designs.
A support processor design relies on specialized microprocessors to help the main CPU perform a variety of functions. These microprocessors may used for input/output, memory management, arithmetic computations, multimedia processing, and telecommunications, thus freeing the main processor to do the primary job of executing program instructions For example, many microcomputers rely on support microprocessors such as arithmetic co-processing load on their main microprocessors. A large computer may use support microprocessors called channels to control the movement of data between the CPU and input/output devices. Advanced microprocessor designs integrate the functions of several support processors on a single main microprocessor.
A coupled processor design uses multiple CPUs or main microprocessors to do multiprocessing, that is, executing more than one instruction at the same time. Some configurations provide a fault-tolerant capability in which multiple CPUs provide a built-in backup to each other should one of them fail.
A parallel processor design uses a group of instruction processors to execute several program instructions at the same time. Some times, hundreds or thousands of processors are organized in clusters or networks in massively parallel processing (MPP) computers. Other parallel processor designs are based on simple models of the human brain called neural networks. All of these systems can execute many instructions at a time in parallel. This is a major departure from the traditional design of current computers, called the Von Neuman design, which executes instructions serially (one at a time). Though difficult to program, many experts consider parallel processor systems the key to providing advanced capabilities to future generations of computers.
RISC Processors:
    Many advanced technical workstations and other computers rely on a processor design called RISC (reduced instruction set computer). This contrasts with most current computers that use CISC (complex instruction set computer) processors. RISC processor designs optimize a CPU’s processing speed by using a smaller instruction set. That is, they use a smaller number of the basic machine instruction that a processor is capable of executing. By keeping the instruction set simpler than CISC processors and using more complex software, a RISC processor can reduce the time needed to execute program instructions.
Computer Processing Speeds:
Computer operating speeds that were formerly measured in milliseconds (thousands of a second) and microseconds (millionths  of a second) are now in the nanosecond (billionth of a second) range, with picosecond (trillionth of a second) speed being attained by some computers. Such speeds seem almost incomprehensible. For example, an average person taking one step each nanosecond would circle the earth above 20 times in one second. Many microcomputers and midrange computers, and most mainframe computers, operate in the nanosecond range, and can thus process program instructions at million instructions per second (MIPS) speeds. Another measure of processing speed is megahertz (MHs), or millions of cycles per second. It is commonly called the clock speed of a microprocessor, sine it is used to rate microprocessors by the speed of their timing circuits or internal clock.
However, megahertz, ratings can be misleading indicators of the effective processing speed of microprocessors as measured in MIPS and other measures. That’s because processing speed depends on a variety of factors besides a microprocessor’s clock speed. Important examples include the size of circuitry paths, or busses, that interconnect microprocessor components, the capacity of instruction processing registers, the use of high-speed memory caches, and the use of specialized microprocessors such as a math co-processor to do arithmetic calculations faster. For example, Intel’s Pentium microprocessor runs at 66 to 200 MHz and is rated at over 100 MIPS, which the Pentium Pro microprocessor has a top processing rating of over 200 MIPS at similar megahertz speeds.

Computer Storage Fundementals and Devices

Data and information must be stored until needed using a variety of storage methods. There are many types of storage media and devices.
Computer Storage Fundamentals:
Data are processed and stored in a computer system through the presence or absence of electronic or magnetic signals in the computer’s circuitry or in the media it uses. This is called a “two-state” or binary representation of data, since the computer and the media can exhibit only two possible states or conditions. For example, transistors other semiconductor circuits are either in a conducting or nonconducting state. Media such as magnetic disks and tapes indicate these two states by having magnetized spots whose magnetic fields have one of two different directions, or polarities. This binary characteristic of computer circuitry and media is what makes the binary number system the basis for representing data in computers. Thus, for electronic circuits, the conducting (ON) state represents the number one, while the nonconducting (OFF) state represents the number zero. For magnetic media, the magnetic field of a magnetized sport in one direction represents a one, while magnetism in the other direction represents a zero.
The smallest element of data is called a bit, which can have a value of either zero or one. The capacity of memory chips is usually expressed in terms of bits. A byte is a basic grouping of bits that the computer operates as a single unit. Typically, it consists of eight bits and represents one character of data in most computer coding schemes. Thus, the capacity of a computer’s memory and secondary storage device is usually expressed in terms of bytes. Computer codes such as ASCII (American Standard Code for Information Interchange) use various arrangements of bits to form bytes that represent the numbers zero through nine, the letters of the alphabets, and many other characters.
Storage capacities are frequently measured in kilobytes (KB), megabytes (MB), gigabytes (GB), or terabytes (TB). Although kilo means 1,000 in the metric system, the computer industry uses K to represents 1,024 or (210) storage positions. Therefore, a capacity of 10 megabytes, for example, is really 10,485,760 storage positions, rather than 10 million positions. However, such differences are frequently disregarded in order to simplify descriptions of storage capacity. Thus, a megabyte is roughly 1 million bytes of storage, while a gigabyte is roughly 1 billion bytes and a terabyte represents about 1 trillion bytes.
Direct and Sequential Access:
Primary storage media such as semiconductor memory chips are called direct access or random access memories (RAM). Magnetic disk devices are frequently called direct access storage devices (DASDs). On the other hand, media such as magnetic tapes are known as sequential access devices.
The term direct access and random access describe the same concept. They mean that an element of data or instructions (such as a byte or word) can be directly stored and retrieved by selecting and using any of the locations on the storage media. They also mean that each storage position (1) has a unique address and (2) can be individually accessed in approximately the same length of time without having to search through other storage positions. For example, each memory cell on a microelectronic semiconductor RAM chip can be individually sensed or changed in the same length of time. Also any data record stored on a magnetic or optical disk can be accessed directly in approximately the same time period.
Sequential access storage media such as magnetic tape do not have unique storage addresses that can be directly addressed. Instead, data must be stored and retrieved using a sequential or serial process. Data are recorded one after another in a predetermined sequence (such as in numeric order) on a storage medium. Locating an individual item of data requires searching much of the recorded data on the tape until the desired item is located.
Semiconductor Memory:
The primary storage (main memory) of your computer consists of microelectronic semiconductor memory chips. Memory chips with capacities of 4 million bits (4 megabits) and 16 megabytes or more of memory chips can be added to your PC to increase its memory capacity. Specialized memory can help improve your computer’s performance. Examples include external cache memory of 256 or 512 kilobytes to help your microprocessor work faster, or a video graphics accelerator card with 2 megabytes or more of RAM for faster and clearer video performance. Removable credit-card-size and smaller “flash memory” RAM cards can also provide several megabytes of erasable direct access storage for PDAs or handheld PCs.
Some of the major attractions of semiconductor memory are its small size, great speed, and shock and temperature resistance. One major disadvantage of most semiconductor memory is its volatility. Uninterrupted electric power must be supplied or the contents of memory will be lost. Therefore, emergency transfer to other devices or standby electrical power (through battery packs or emergency generators) is required if data are to be saved. Another alternative is to permanently “burn in” the contents of semiconductor devices so that they cannot be erased by a loss of power.
Thus, there are two basic types of semiconductor memory: random access memory (RAM) and read only memory (ROM).
random access memory. These memory chips are the most widely used primary storage medium. Each memory position can be both sensed (read) and changed (written), so it is also called read/write memory. This is a volatile memory.
read only memory. Nonvolatile random access memory chips are used for permanent storage. ROM can be read but not erased or overwritten.
Frequently used control instructions in the control unit and programs in primary storage (such as parts of the operating system) can be permanently burned in to the storage cells during manufacture. This is sometimes called firmware. Variations include PROM (programmable read only memory) and EPROM (erasable programmable read only memory) that can be permanently or temporarily programmed after manufacture.
Magnetic Disk Storage:
Magnetic disks are the most common form of secondary storage for your computer system. That’s because they provide fast access and high storage capacities at a reasonable cost. Magnetic disk drives contain metal disks that are coated on both sides with an iron oxide recording material. Several disks are mounted together on a vertical shaft, which typically rotates the disks at speeds of 3,600 to 7,600 revolutions per minute (rpm). Electromagnetic read/write heads are positioned by access arms between the slightly separated disks to read and write data on concentric, circular tracks. Data are recorded on tracks in the form of tiny magnetized spots to form the binary digits of common computer codes. Thousands of bytes can be recorded on each tracks, and there are several hundred data tracks on each disk surface, thus providing you with billions of storage positions for your software and data.
Types of Magnetic Disks:
There are several types of magnetic disk arrangements, including removable disk cartridges as well as fixed disk units. Removable disk devices are popular because they are transportable and can be used to store backup copies of your data offline for convenience and security.
Floppy disks or magnetic diskettes, consist of polyester film disks covered with an iron oxide compound. A single disk is mounted and rotates  freely inside a protective flexible or hard plastic jacket, which has access openings to accommodate the read/write head of a disk drive unit. The 31/2 inch floppy disk, with capacities of 1.44 megabytes, is the most widely used version, with a newer LS-120 technology offering 120 megabytes of storage.
Hard disk drives combine magnetic disks, access arms, and read/write heads into a sealed module. This allows higher speeds, greater data-recording densities, and closer tolerances within a sealed, more stable environment. Fixed or removable disk cartridge versions are available. Capacities of hard drives range from several hundred megabytes to gigabytes of storage.
 Disk arrays of interconnected microcomputer hard disk drives have replaced large-capacity mainframe disk drives to provide many gigabytes of online storage. Known as RAID (redundant arrays of independent disks), they combine from 6 to more than 100 small hard disk drives and their control microprocessors into a single unit. RAID units provide large capacities with high access speeds since data are accessed in parallel over multiple paths from many disks. RAID units also provide a fault tolerant capability, since their redundant design offers multiple copies of data on several disks. If one disk fails, data can be recovered from backup copies automatically stored on other disks.
Magnetic Tape Storage:
Magnetic tape is still being used as a secondary storage medium in business applications. They read/write heads of magnetic tape drives record data in the form of magnetized spots on the iron oxide coating of the plastic tape. Magnetic tape devices include tape reels and cartridges in mainframes and midrange systems, and small cassettes or cartridges for PCs. Magnetic tape cartridges have replaced tape reels in many applications, and can hold over 200 megabytes.
One growing business application of magnetic tape involves the use of 36-track magnetic tape cartridges in robotic automated drive assemblies that can hold hundreds of cartridges. These devices serve as slower, but lower cost, storage to supplement magnetic disks to meet massive data warehouse and other business storage requirements. Other major applications for magnetic tape includes long-term archival storage and backup storage for PCs and other systems.
Optical Disk Storage:
Optical disks are a fast-growing storage medium. The version for use with micro computers is called CD-ROM (compact disk- read only memory). CD-ROM technology use 12-centimeter (4.7 inch) compact disks (CDs) similar to those used in stereo music systems. Each disk can store more than 600 megabytes. That’s the equivalent of over 400 1.44 megabyte floppy disks or more than 300,000 double-spaced pages of text. A laser records data by burning permanent microscopic pits in a spiral track on a master disk from which compact disks can be mass produced. Then CD-ROM disk drives use a laser device to read the binary codes formed by those pits.
CD-R (compact disk – record able) is another optical disk technology. It enables computers with CD-R disk drive units to record their own data once on a CD, then be able to read the data indefinitely. The major limitation of CD-ROM and CD-R disks is that recorded data cannot be erased. However, CD-RW
(CD-rewritable) optical disk systems have now become available which record and erase data by using a laser to heat a microscopic point on the disk’s surface. In CD-RW versions using magneto optical technology, a magnetic coil changes the spot’s reflective properties from one direction to another, thus recording a binary one or zero. A laser device can then read the binary codes on the disk by sensing the direction of reflected light.
Optical disk capacities and capabilities have increased dramatically with the emergence of an optical disk technology called DVD (digital video disk or digital versatile disk), which can hold from 4.0 to 8.5 gigabytes of multimedia data on each side of a compact disk. The large capacities and high quality images and sound of DVD technology are expected to eventually replace CD-ROM and CD-RW technologies for data storage, and promise to accelerate the sue of DVD drives for multimedia products that can be used in both computers and home entertainment systems.
Blu-Ray and HD-DVD are two new optical storage technologies that fight as the successor of DVD. Both HD-DVD and Blu-ray are high-definition optical disc formats, incompatible with each other. They were meant to replace the existing DVD format, which was and still is used by a large user community. HD-DVDs and Blu-ray discs are similar in terms of the higher storage capacities and a superior picture quality offered by them. Their storage capacities are higher than those of CDs and DVDs. However, a single layer HD-DVD can store 15 GB data whereas a single-layer Blu-ray disc stores 25 GB data.

Major Types of  Computer Systems

Microcomputer Systems:
Microcomputers are the most important category of computer systems for end users. Though usually called a personal computer, or PC, a microcomputer is much more than a small computer for use by an individual. The computing power of microcomputers now exceeds that of the mainframes of previous computer generations at a fraction of their cost. Thus, they have become powerful networked professional work stations for end users in business.
Microcomputers come in a variety of sizes and shapes for a variety of purposes. For example, PCs are available as handhled, notebook, laptop, portable, desktop, and floor-standing models.  Based on their use, they include home, personal, professional, workstation, and multi-user systems. Most microcomputers are desktops designed to fit on an office desk, or notebooks for those who want a small, portable PC for their work activities.
Some microcomputers are powerful workstation computers (technical work-stations) that support applications with heavy mathematical computing and graphics display demands such as computer-aided design (CAD) in engineering, or investment and portfolio analysis in the securities industry. Other microcomputers are used as network servers. They are usually more powerful microcomputers that coordinate telecommunications and resource sharing in small local area networks (LANs), and Internet and intranet Web sites. Another important microcomputer category includes handheld microcomputer devices known as personal digital assistants (PDAs), designed for convenient mobile communications and computing. PDAs use touch-screens, pen-based handwriting recognition of keyboards to help mobile workers send and receive E-mail and exchange information such as appointments, to do lists, and scales contacts with their desktop PCs or Web servers.
Multimedia Computer Systems:
Multimedia PCs are designed to present you with information in a variety of media, including text and graphics displays, voice and other digitized audio, photographs, animation, and video clips. Mention multimedia, and many people think of computer video games, multimedia encyclopedias, educational videos, and multimedia home pages on the World Wide Web. However, multimedia systems are widely used in business for training employees, educating customers, making sales presentations, and adding impact to other business presentations.
The basic hardware and software requirements of a multimedia computer system depend on whether you wish to create as well as enjoy multimedia presentations. Owners of low-cost multimedia PCs marketed for home used do not need authoring software or high-powered hardware capacities in order to enjoy multimedia games and other entertainment and educational multimedia products. These computers come equipped with a CD-ROM drive, stereo speakers, additional memory, a high-performance processor, and other multimedia processing capabilities.
People who want to create their own multimedia production may have to spend several thousand dollars to put together a high-performance multimedia authoring system. This includes a high-resolution color graphics monitor, sound and video capture boards, a high-performance microprocessor with multimedia capabilities, additional megabytes of memory, and several gigabytes of hard disk capacity. Sound cards and video capture boards are circuit boards that contain digital signal processors (DSPs) and additional megabytes of memory for digital processing of sound and video. A digital camera, digital video camcorder, optical scanner, and software such as authoring tools and programs for image editing and graphics creation can add several thousand dollars to the star-up costs of a multimedia authoring system.
Midrange Computer Systems:
Midrange Computers, including minicomputers and high-end network servers, are multi-user systems that can manage network of PCs and terminals. Though not as powerful as mainframe computers, they are less costly to buy, operate, and maintain than mainframe systems, and thus meet the computing needs of many organizations.
Midrange computers first became popular as minicomputers for scientific research, instrumentation systems, and industrial process monitoring and control. Minicomputers could easily handle such uses because these applications are narrow in scope and do not demand the processing versatility of mainframe systems. Thus, midrange computers serve as industrial process-control and manufacturing plant computers, and they still play a major role in computer-aided manufacturing (CAM). They can also take the form of powerful technical workstations for computer-aided design (CAD) and other computation and graphics-intensive applications. Midrange computers are also used as front-end computers to assist mainframe computers in telecommunication processing and network management.
Midrange computers have become popular as powerful network servers to help manage large Internet Web sites, corporate intranets and extranets, and client/server networks. Electronic commerce and other business uses of the Internet are popular high-end server applications, as are integrated enterprise wide manufacturing, distribution and financial applications. Other applications, like data warehouse management, data mining, and online analytical processing.
Mainframe Computer Systems:
Mainframe computes are large, fast, and powerful computer systems. For example, mainframes can process hundreds of million instructions per second (MIPS). Mainframes also have large primary storage capacities. Their main memory capacity can range from hundreds of megabytes to many gigabytes of primary storage. And mainframes have slimmed down drastically in the last few years, dramatically reducing their air-conditioning needs, electrical power consumption, and floor space requirements, and thus their acquisition and operating costs. Most of these improvements are the result of a move from water-cooled mainframes to a new CMOS air-cooled technology for mainframe systems.
Thus, mainframe computers continue to handle the information processing needs of major corporations and government agencies with many employees and customers or with complex computational problems. For example, major international banks, airlines, oil companies, and other large corporations process millions of sales transactions and customer inquiries each day with the help of large mainframe systems. Mainframes are still used for computation-intensive applications such as analyzing seismic data from oil field explorations or simulating flight conditions in designing aircraft. Mainframes are also widely used as super server for the large client/server network and high-volume Internet Web sites of large companies.
Supercomputer Systems:
The term supercomputer describes a category of extremely powerful computer systems specifically designed for scientific ,engineering, and business applications requiring extremely high speeds for massive numeric computations. The market for supercomputers includes government research agencies, large universities, and major corporations. They use supercomputers for applications such as global weather forecasting, military defense systems, computational cosmology and astronomy, microprocessor research and design, large-scale data mining and so on.
Supercomputers use parallel processing architectures of interconnected microprocessors (which can execute many instructions at the same time in parallel). They can perform arithmetic calculations at speeds of billions of floating-point operations per second (gigaflops). Teraflop (1 trillion floating-point operations per second) supercomputers, which use advanced massively parallel processing (MPP) designs of thousands of interconnected microprocessors, are becoming available. Purchase prices for large supercomputers are in the $5 million to $50 million range.
However, the use of symmetric multiprocessing (SMP) and distributed shared memory (DSM) designs of smaller numbers of interconnected microprocessors has spawned a breed of minisuper computers with prices that start in the hundreds of thousands of dollars.