Inside this Article

1. Introduction to How Holographic Memory Will Work
2. A Little Background
3. The Basics

4. Desktop Holographic Data Storage
5. Lots More Information
6. See all Memory articles

Computer Memory Image Gallery

In a holographic memory device, a laser beam is split in two, and the two resulting beams interact in a crystal medium to store a holographic recreation of a page of data.  See more pictures of computer memory.

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• Bios Quiz
• Computer Memory
• HowStuffWorks Forums: What do you think the first consumer product to use holographic memory will be?
• Curiosity Project: Can you compare computer processing to thinking?

Devices that use light to store and read data have been the backbone of data storage for nearly two decades. Compact discsrevolutionized data storage in the early 1980s, allowing multi-megabytes of data to be stored on a disc that has a diameter of a mere 12 centimeters and a thickness of about 1.2 millimeters. In 1997, an improved version of the CD, called a digital versatile disc(DVD), was released, which enabled the storage of full-length movies on a single disc.

CDs and DVDs are the primary data storage methods for music, software, personal computing and video. A CD can hold 783 megabytes of data, which is equivalent to about one hour and 15 minutes of music, but Sony has plans to release a 1.3-gigabyte (GB) high-capacity CD. A double-sided, double-layer DVD can hold 15.9 GB of data, which is about eight hours of movies. These conventional storage mediums meet today's storage needs, but storage technologies have to evolve to keep pace with increasing consumer demand. CDs, DVDs and magnetic storage all store bits of information on the surface of a recording medium. In order to increase storage capabilities, scientists are now working on a new optical storage method, called holographic memory, that will go beneath the surface and use the volume of the recording medium for storage, instead of only the surface area.

Three-dimensional data storage will be able to store more information in a smaller space and offer faster data transfer times. In this article, you will learn how a holographic storage system might be built in the next three or four years, and what it will take to make a desktop version of such a high-density storage system.Click here for more details

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A courtroom photo of David L. Smith, the alleged creator of the Melissa virus.

Daniel Hulshizer/AFP/Getty Images

10: Melissa

In the spring of 1999, a man named David L. Smith created acomputer virus based on a Microsoft Word macro. He built the virus so that it could spread through e-mail messages. Smith named the virus "Melissa," saying that he named it after an exotic dancer from Florida [source: CNN].

Rather than shaking its moneymaker, the Melissa computer virus tempts recipients into opening a document with an e-mail message like "Here is that document you asked for, don't show it to anybody else." Once activated, the virus replicates itself and sends itself out to the top 50 people in the recipient's e-mail address book.

The virus spread rapidly after Smith unleashed it on the world. The United States federal government became very interested in Smith's work -- according to statements made by FBI officials to Congress, the Melissa virus "wreaked havoc on government and private sector networks" [source: FBI]. The increase in e-mail traffic forced some companies to discontinue e-mail programs until the virus was contained.

After a lengthy trial process, Smith lost his case and received a 20-month jail sentence. The court also fined Smith $5,000 and forbade him from accessing computer networks without court authorization [source:BBC]. Ultimately, the Melissa virus didn't cripple the Internet, but it was one of the first computer viruses to get the public's attention.

Flavors of Viruses

In this article, we'll look at several different kinds of computer viruses. Here's a quick guide to what we'll see:

• The general term computer virus usually covers programs that modify how a computer works (including damaging the computer) and can self-replicate. A true computer virus requires a host program to run properly -- Melissa used a Word document.
• A worm, on the other hand, doesn't require a host program. It's an application that can replicate itself and send itself through computer networks.
• Trojan horses are programs that claim to do one thing but really do another. Some might damage a victim's hard drive. Others can create a backdoor, allowing a remote user to access the victim's computer system.

Next, we'll look at a virus that had a sweet name but a nasty effect on its victims.

OLD-SCHOOL VIRUSES

Some of the earliest viruses to infect personal computers included the Apple Viruses, which attacked Apple II computers.

Inside this Article

1. Introduction to How Cloud Computing Works
2. Cloud Computing Architecture
3. Cloud Computing Applications

4. Cloud Computing Concerns
5. Lots More Information
6. See all Cloud Computing articles

Computer Networking Image Gallery

A typical cloud computing system. See more computer networking pictures.

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MORE COMPUTING

• Shared Computing
• Utility Computing
• Grid Computing
• Curiosity Project: What is ubiquitous computing?

Let's say you're an executive at a large corporation. Your particular responsibilities include making sure that all of your employees have the right hardware and software they need to do their jobs. Buying computers for everyone isn't enough -- you also have to purchase software or software licenses to give employees the tools they require. Whenever you have a new hire, you have to buy more software or make sure your current software license allows another user. It's so stressful that you find it difficult to go to sleep on your huge pile of money every night.

Soon, there may be an alternative for executives like you. Instead of installing a suite of software for each computer, you'd only have to load one application. That application would allow workers to log into a Web-based service which hosts all the programs the user would need for his or her job. Remote machines owned by another company would run everything from e-mail to word processing to complex data analysis programs. It's called cloud computing, and it could change the entire computer industry.

In a cloud computing system, there's a significant workload shift. Local computers no longer have to do all the heavy lifting when it comes to running applications. The network of computers that make up the cloud handles them instead. Hardware and software demands on the user's side decrease. The only thing the user's computer needs to be able to run is the cloud computing system's interface software, which can be as simple as a Web browser, and the cloud's network takes care of the rest.

There's a good chance you've already used some form of cloud computing. If you have an e-mail account with a Web-based e-mail service like Hotmail, Yahoo! Mail or Gmail, then you've had some experience with cloud computing. Instead of running an e-mail program on your computer, you log in to a Web e-mail account remotely. The software and storage for your account doesn't exist on your computer -- it's on the service's computer cloud.

What makes up a cloud computing system? Find out in the next section.Click here for more details

Compiled by Brian Krebs

washingtonpost.com Staff Writer
Friday, February 14, 2003;

1945: Rear Admiral Grace Murray Hopper discovers a moth trapped between relays in a Navy computer. She calls it a "bug," a term used since the late 19th century to refer to problems with electrical devices. Murray Hopper also coined the term "debugging" to describe efforts to fix computer problems.
1949: Hungarian scientist John von Neumann (1903-1957) devises the theory of self-replicating programs, providing the theoretical foundation for computers that hold information in their "memory."

_____Web Special_____  • Cyber-Attacks by Al Qaeda Feared (The Washington Post, Jun 27, 2002)  • White House Pushing Cybersecurity Insurance(washingtonpost.com, Jun 27, 2002) • Related Documents and Resources On The Web(washingtonpost.com, May 16, 2003)  • Timeline: The U.S. Government and Cybersecurity(washingtonpost.com, May 16, 2003)  • Key Players in U.S. Government's Cybersecurity Efforts(washingtonpost.com, May 16, 2003)  _____Cyber-Security_____  • Va. Lawmakers Aim to Hook Cyberscammers (The Washington Post, Apr 10, 2005)  • Net Aids Access to Sensitive ID Data (The Washington Post, Apr 4, 2005)  • Microsoft Seeks to Identify Phishing Scam Authors(washingtonpost.com, Mar 31, 2005) • More Security News  Free E-mail Newsletters TechNews Daily Report See a Sample  |  Sign Up Now Personal Finance See a Sample  |  Sign Up Now Personal Tech See a Sample  |  Sign Up Now

1960: AT&T introduces its Dataphone, the first commercial modem.
1963: Programmers develop the American Standard Code for Information Interchange (ASCII), a simple computer language that allows machines produced by different manufacturers to exchange data.
1964: AT&T begins monitoring telephone calls to try to discover the identities of "phone freaks," or "phreakers," who use "blue boxes" as tone generators to make free phone calls. The team's surveillance chief tells Newsweek magazine in 1975 that the company monitored 33 million toll calls to find phreakers. AT&T scores 200 convictions by the time the investigation ends in 1970.
1969: Programmers at AT&T's Bell Laboratories develop the UNIX operating system, the first multi-tasking operating system.
1969: The Advanced Research Projects Agency launches ARPANET, an early network used by government research groups and universities, and the forerunner of the Internet.
1972: John Draper, soon to be known as "Captain Crunch," discovers that the plastic whistle in a box of breakfast cereal reproduces a 2600-hertz tone. With a blue box, the whistle unlocks AT&T's phone network, allowing free calls and manipulation of the network. Among other phreakers of the 1970s is famous future hacker Kevin Mitnick.
1972: Future Apple Computer co-founder Steve Wozniak builds his own "blue box." Wozniak sells the device to fellow University of California-Berkeley students.
1974: Telenet, a commercial version of ARPANET, debuts.
1979: Engineers at Xerox Palo Alto Research Center discover the computer "worm," a short program that scours a network for idle processors. Designed to provide more efficient computer use, the worm is the ancestor of modern worms -- destructive computer viruses that alter or erase data on computers, often leaving files irretrievably corrupted.
1983: The FBI busts the "414s," a group of young hackers who break into several U.S. government networks, in some cases using only an Apple II+ computer and a modem.
1983: University of Southern California doctoral candidate Fred Cohen coins the term "computer virus" to describe a computer program that can "affect other computer programs by modifying them in such a way as to include a (possibly evolved) copy of itself." Anti-virus makers later capitalize on Cohen's research on virus defense techniques.
1984: In his novel, "Neuromancer," author William Gibson popularizes the term "cyberspace," a word he used to describe the network of computers through which the characters in his futuristic novels travel.
1986: One of the first PC viruses ever created, "The Brain," is released by programmers in Pakistan.
1988: Twenty-three-year-old programmer Robert Morris unleashes a worm that invades ARPANET computers. The small program disables roughly 6,000 computers on the network by flooding their memory banks with copies of itself. Morris confesses to creating the worm out of boredom. He is fined $10,000 and sentenced to three years' probation.
1991: Programmer Philip Zimmerman releases "Pretty Good Privacy" (PGP), a free, powerful data-encryption tool. The U.S. government begins a three-year criminal investigation on Zimmerman, alleging he broke U.S. encryption laws after his program spread rapidly around the globe. The government later drops the charges.
1991: Symantec releases the Norton Anti-Virus software.
1994: Inexperienced e-mail users dutifully forward an e-mail warning people not to open any message with the phrase "Good Times" in the subject line. The missive, which warns of a virus with the power to erase a recipient's hard drive, demonstrates the self-replicating power of e-mail virus hoaxes that continue to circulate in different forms today.
1995: Microsoft Corp. releases Windows 95. Anti-virus companies worry that the operating system will be resistant to viruses. Later in the year, however, evolved "macro" viruses appear that are able to corrupt the new Windows operating system.
1998: Intruders infiltrate and take control of more than 500 military, government and private sector computer systems. The incidents -- dubbed "Solar Sunrise" after the well-known vulnerabilities in computers run on the Sun Solaris operating system -- were thought to have originated from operatives in Iraq. Investigators later learn that two California teenagers were behind the attacks. The experience gives the Defense Department its first taste of what hostile adversaries with greater skills and resources would be able to do to the nation's command and control center, particularly if used in tandem with physical attacks.
1999: The infamous "Melissa" virus infects thousands of computers with alarming speed, causing an estimated $80 million in damage and prompting record sales of anti-virus products. The virus starts a program that sends copies of itself to the first 50 names listed in the recipient's Outlook e-mail address book. It also infects Microsoft Word documents on the user's hard drive, and mails them out through Outlook to the same 50 recipients.
2000: The "I Love You" virus infects millions of computers virtually overnight, using a method similar to the Melissa virus. The virus also sends passwords and usernames stored on infected computers back to the virus's author. Authorities trace the virus to a young Filipino computer student who goes free because the Philippines has no laws against hacking and spreading computer viruses. This spurs the creation of the European Union's global Cybercrime Treaty.
2000: Yahoo, eBay, Amazon, Datek and dozens of other high-profile Web sites are knocked offline for up to several hours following a series of so-called "distributed denial-of-service attacks." Investigators later discover that the DDOS attacks -- in which a target system is disabled by a flood of traffic from hundreds of computers simultaneously -- were orchestrated when the hackers co-opted powerful computers at the University of California-Santa Barbara.
2001: The "Anna Kournikova" virus, promising digital pictures of the young tennis star, mails itself to every person listed in the victim's Microsoft Outlook address book. This relatively benign virus frightens computer security analysts, who believe it was written using a software "toolkit" that allows even the most inexperienced programmer to create a computer virus.
2001: The Code Red worm infects tens of thousands of systems running Microsoft Windows NT and Windows 2000 server software, causing an estimated $2 billion in damages. The worm is programmed to use the power of all infected machines against the White House Web site at a predetermined date. In an ad hoc partnership with virus hunters and technology companies, the White House deciphers the virus's code and blocks traffic as the worm begins its attack.
2001: Debuting just days after the Sept. 11 attacks, the "Nimda" virus infects hundreds of thousands of computers around the world. The virus is considered one of the most sophisticated, with up to five methods of infecting systems and replicating itself.
2001: Melissa virus author David L. Smith, 33, is sentenced to 20 months in federal prison.
2002: The "Klez" worm -- a bug that sends copies of itself to all of the e-mail addresses in the victim's Microsoft Outlook directory -- begins its march across the Web. The worm overwrites files and creates hidden copies of the originals. The worm also attempts to disable some common anti-virus products and has a payload that fills files with all zeroes. Variants of the Klez worm remain the most active on the Internet.
2002: A denial-of-service attack hits all 13 of the "root" servers that provide the primary roadmap for almost all Internet communications. Internet users experience no slowdowns or outages because of safeguards built into the Internet's architecture. But the attack -- called the largest ever -- raises questions about the security of the core Internet infrastructure.
2003: The "Slammer" worm infects hundreds of thousands of computers in less than three hours. The worm ever wreaks havoc on businesses worldwide, knocking cash machines offline and delaying airline flights. It holds the ranking as the fastest-spreading computer worm ever.

2004: The "MyDoom" worm becomes the fastest-spreading e-mail worm as it causes headaches -- but very little damage -- almost a year to the day after Slammer ran rampant in late January 2003. MyDoom uses "social engineering," or low-tech psychological tricks, to persuade people to open the e-mail attachment that contains the virus. It claims to be a notification that an e-mail message sent earlier has failed, and prompts the user to open the attachment to see what the message text originally said. Many people fall for it.

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********* Hit here for more details *********MS-DOS ( /ˌɛmɛsˈdɒs/ em-es-doss; short for Microsoft Disk Operating System) is an operating system for x86-based personal computers. It was the most commonly used member of the DOS family of operating systems, and was the main operating system for IBM PC compatible personal computers during the 1980s to the mid 1990s, until it was gradually superseded by operating systems offering a graphical user interface (GUI), in particular by various generations of the Microsoft Windows operating system.

MS-DOS grew from a 1981 request by IBM for an operating system for its IBM PC range of personal computers. Microsoft quickly bought the rights toQDOS (Quick and Dirty Operating System), also known as 86-DOS,^[2] from Seattle Computer Products, and began work on modifying it to meet IBM's specification. The first edition, MS-DOS 1.0, was launched in 1982.^[3] The version shipped with IBM's PCs was called PC DOS. Although MS-DOS and PC-DOS were initially developed in parallel by Microsoft and IBM, the two products eventually went their separate ways.

During its life, several competing products were released for the x86 platform,^[4] and MS-DOS itself would go through eight versions, until development ceased in 2000. Ultimately it was the key product in Microsoft's growth from a programming languages company to a diverse software development firm, providing the company with essential revenue and marketing resources. It was also the underlying basic operating system on which early versions of Windows ran as a GUI.

Contents   [hide]  1 History 2 Versions 3 Competition 4 Legal issues 5 Use of undocumented APIs 6 End of MS-DOS 7 The Windows command-line interface 8 Legacy compatibility 9 Related systems 9.1 Single-user 10 See also 11 Quotations 12 Remarks 13 Notes 14 References 15 External links

MS-DOS

An example of MS-DOS's command-line interface, this one showing that the current directory is the root of drive C.
Company /developer	Microsoft Corporation
Programmed in	Assembly language[1]
OS family	DOS
Working state	Discontinued/Historic
Source model	Closed source
Initial release	1981
Latest stable release	8.0 / September 14, 2000; 11 years ago
Availablelanguage(s)	Multilanguage
Availableprogramming languages(s)	C, Pascal, QBasic,Batch, etc.
Supported platforms	x86
Kernel type	Monolithic kernel
Default user interface	Command-line interface, Text user interface
License	Proprietary