Saturday, January 23, 2010

Working of Routing Algorithms

How Routing Algorithms Work



algorithm
Think you know how routers work? These devices use intricate formulas to figure out exactly where to send a packet and how to get it there.

If you have read the article How Routers Work, then you know that a router is used to manage network traffic and find the best route for sending packets. But have you ever thought about how routers do this? Routers need to have some information about network status in order to make decisions regarding how and where to send packets. But how do they gather this information?

In this article, we'll find out precisely what information is used by routers in determining where to send a packet.

The Basics

Routers use routing algorithms to find the best route to a destination. When we say "best route," we consider parameters like the number of hops (the trip a packet takes from one router or intermediate point to another in the network), time delay and communication cost of packet transmission.




Based on how routers gather information about the structure of a network and their analysis of information to specify the best route, we have two major routing algorithms: global routing algorithms and decentralized routing algorithms. In decentralized routing algorithms, each router has information about the routers it is directly connected to -- it doesn't know about every router in the network. These algorithms are also known as DV (distance vector) algorithms. In global routing algorithms, every router has complete information about all other routers in the network and the traffic status of the network. These algorithms are also known as LS (link state) algorithms. We'll discuss LS algorithms in the next .

LS Algorithms

In LS algorithms, every router has to follow these steps:
  1. Identify the routers that are physically connected to them and get their IP addresses
    When a router starts working, it first sends a "HELLO" packet over network. Each router that receives this packet replies with a message that contains its IP address.
  2. Measure the delay time (or any other important parameters of the network, such as average traffic) for neighbor routers
    In order to do that, routers send echo packets over the network. Every router that receives these packets replies with an echo reply packet. By dividing round trip time by 2, routers can count the delay time. (Round trip time is a measure of the current delay on a network, found by timing a packet bounced off some remote host.) Note that this time includes both transmission and processing times -- the time it takes the packets to reach the destination and the time it takes the receiver to process it and reply.
  3. Broadcast its information over the network for other routers and receive the other routers' information
    In this step, all routers share their knowledge and broadcast their information to each other. In this way, every router can know the structure and status of the network.
  4. Using an appropriate algorithm, identify the best route between two nodes of the network
    In this step, routers choose the best route to every node. They do this using an algorithm, such as the Dijkstra shortest path algorithm. In this algorithm, a router, based on information that has been collected from other routers, builds a graph of the network. This graph shows the location of routers in the network and their links to each other. Every link is labeled with a number called the weight or cost. This number is a function of delay time, average traffic, and sometimes simply the number of hops between nodes. For example, if there are two links between a node and a destination, the router chooses the link with the lowest weight.
The Dijkstra algorithm goes through these steps:

  1. The router builds a graph of the network and identifies source and destination nodes, as V1 and V2 for example. Then it builds a matrix, called the "adjacency matrix." In this matrix, a coordinate indicates weight. For example, [i, j] is the weight of a link between Vi and Vj. If there is no direct link between Vi and Vj, this weight is identified as "infinity."
  2. The router builds a status record set for every node on the network. The record contains three fields:

    • Predecessor field - The first field shows the previous node.
    • Length field - The second field shows the sum of the weights from the source to that node.
    • Label field - The last field shows the status of node. Each node can have one status mode: "permanent" or "tentative."



  3. The router initializes the parameters of the status record set (for all nodes) and sets their length to "infinity" and their label to "tentative."
  4. The router sets a T-node. For example, if V1 is to be the source T-node, the router changes V1's label to "permanent." When a label changes to "permanent," it never changes again. A T-node is an agent and nothing more.
  5. The router updates the status record set for all tentative nodes that are directly linked to the source T-node.
  6. The router looks at all of the tentative nodes and chooses the one whose weight to V1 is lowest. That node is then the destination T-node.
  7. If this node is not V2 (the intended destination), the router goes back to step 5.
  8. If this node is V2, the router extracts its previous node from the status record set and does this until it arrives at V1. This list of nodes shows the best route from V1 to V2.

Working of Fiber Optics

How Fiber Optics Work

You hear about fiber-optic cables whenever people talk about the telephone system, the cable TV system or the Internet. Fiber-optic lines are strands of optically pure glass as thin as a human hair that carry digital information over long distances. They are also used in medical imaging and mechanical engineering inspection.







Parts of a single optical fiber
In this article, we will show you how these tiny strands of glass transmit light and the fascinating way that these strands are made.

What are Fiber Optics?

Fiber optics (optical fibers) are long, thin strands of very pure glass about the diameter of a human hair. They are arranged in bundles called optical cables and used to transmit light signals over long distances.
If you look closely at a single optical fiber, you will see that it has the following parts:
  • Core - Thin glass center of the fiber where the light travels
  • Cladding - Outer optical material surrounding the core that reflects the light back into the core
  • Buffer coating - Plastic coating that protects the fiber from damage and moisture
Hundreds or thousands of these optical fibers are arranged in bundles in optical cables. The bundles are protected by the cable's outer covering, called a jacket. Optical fibers come in two types:
  • Single-mode fibers
  • Multi-mode fibers

Single-mode fibers have small cores (about 3.5 x 10-4 inches or 9 microns in diameter) and transmit infrared laser light (wavelength = 1,300 to 1,550 nanometers). Multi-mode fibers have larger cores (about 2.5 x 10-3 inches or 62.5 microns in diameter) and transmit infrared light (wavelength = 850 to 1,300 nm) from light-emitting diodes (LEDs).
Some optical fibers can be made from plastic. These fibers have a large core (0.04 inches or 1 mm diameter) and transmit visible red light (wavelength = 650 nm) from LEDs.
Let's look at how an optical fiber works.

How Does an Optical Fiber Transmit Light?

Suppose you want to shine a flashlight beam down a long, straight hallway. Just point the beam straight down the hallway -- light travels in straight lines, so it is no problem. What if the hallway has a bend in it? You could place a mirror at the bend to reflect the light beam around the corner. What if the hallway is very winding with multiple bends? You might line the walls with mirrors and angle the beam so that it bounces from side-to-side all along the hallway. This is exactly what happens in an optical fiber.








Diagram of total internal reflection in an optical fiber


The light in a fiber-optic cable travels through the core (hallway) by constantly bouncing from the cladding (mirror-lined walls), a principle called total internal reflection. Because the cladding does not absorb any light from the core, the light wave can travel great distances.
However, some of the light signal degrades within the fiber, mostly due to impurities in the glass. The extent that the signal degrades depends on the purity of the glass and the wavelength of the transmitted light (for example, 850 nm = 60 to 75 percent/km; 1,300 nm = 50 to 60 percent/km; 1,550 nm is greater than 50 percent/km). Some premium optical fibers show much less signal degradation -- less than 10 percent/km at 1,550 nm.

working of Routers

How Routers Work

router
Fujitsu GeoStream R980 industrial strength router.



The Internet is one of the 20th century's greatest communications developments. It allows people around the world to send e-mail to one another in a matter of seconds.

We're all used to seeing the various parts of the Internet that come into our homes and offices -- the Web pages, e-mail messages and downloaded files that make the Internet a dynamic and valuable medium. But none of these parts would ever make it to your computer without a piece of the Internet that you've probably never seen. In fact, most people have never stood "face to machine" with the technology most responsible for allowing the Internet to exist at all: the router.




Keeping the Messages Moving

When you send e-mail to a friend on the other side of the country, how does the message know to end up on your friend's computer, rather than on one of the millions of other computers in the world? Much of the work to get a message from one computer to another is done by routers, because they're the crucial devices that let messages flow between networks, rather than within networks.



Let's look at what a very simple router might do. Imagine a small company that makes animated 3-D graphics for local television stations. There are 10 employees of the company, each with a computer. Four of the employees are animators, while the rest are in sales, accounting and management. The animators will need to send lots of very large files back and forth to one another as they work on projects. To do this, they'll use a network.
When one animator sends a file to another, the very large file will use up most of the network's capacity, making the network run very slowly for other users. One of the reasons that a single intensive user can affect the entire network stems from the way that Ethernet works. Each information packet sent from a computer is seen by all the other computers on the local network. Each computer then examines the packet and decides whether it was meant for its address. This keeps the basic plan of the network simple, but has performance consequences as the size of the network or level of network activity increases. To keep the animators' work from interfering with that of the folks in the front office, the company sets up two separate networks, one for the animators and one for the rest of the company. A router links the two networks and connects both networks to the Internet.

Directing Traffic

The router is the only device that sees every message sent by any computer on either of the company's networks. When the animator in our example sends a huge file to another animator, the router looks at the recipient's address and keeps the traffic on the animator's network. When an animator, on the other hand, sends a message to the bookkeeper asking about an expense-account check, then the router sees the recipient's address and forwards the message between the two networks.
One of the tools a router uses to decide where a packet should go is a configuration table. A configuration table is a collection of information, including:
  • Information on which connections lead to particular groups of addresses
  • Priorities for connections to be used
  • Rules for handling both routine and special cases of traffic
A configuration table can be as simple as a half-dozen lines in the smallest routers, but can grow to massive size and complexity in the very large routers that handle the bulk of Internet messages. A router, then, has two separate but related jobs:
  • The router ensures that information doesn't go where it's not needed. This is crucial for keeping large volumes of data from clogging the connections of "innocent bystanders."
  • The router makes sure that information does make it to the intended destination.
In performing these two jobs, a router is extremely useful in dealing with two separate computer networks. It joins the two networks, passing information from one to the other and, in some cases, performing translations of various protocols between the two networks. It also protects the networks from one another, preventing the traffic on one from unnecessarily spilling over to the other. As the number of networks attached to one another grows, the configuration table for handling traffic among them grows, and the processing power of the router is increased. Regardless of how many networks are attached, though, the basic operation and function of the router remains the same. Since the Internet is one huge network made up of tens of thousands of smaller networks, its use of routers is an absolute necessity.

Tuesday, January 19, 2010

Working of Nintendo 64

How N64 Works


History

Just as Atari ushered in the dawn of the home video game, Nintendo is largely considered to be the company that revolutionized the industry with the introduction of the Nintendo Entertainment System (NES) in 1985. An 8-bit system based on the 6502 processor and some custom chips, the NES came together with Super Mario Brothers; this inclusion of an accurate home version of one of the most popular arcade games at the time turned out to be pure genius. Sales of the NES were phenomenal. This established Nintendo as the dominant home video game manufacturer until the late '90s, when it was eclipsed by the rival Sony PlayStation.



Working of Dreamcast

How Dreamcast Works




dreamcast console
Sega Dreamcast hit the market in 1999 and was hailed as an innovative video game system.

With good reason, Popular Science magazine recognized the Sega Dreamcast as one of the most important and innovative products of 1999. Impressive technical specifications, great games and an imaginative advertising campaign heralded the arrival of the latest system from a company known for groundbreaking Video game systems.­

In this edition , you will learn about this phenomenal system, the revolutionary controller that it uses and the proprietary optical storage method chosen by Sega. You will also learn about the VMS, a versatile option that can be used all by itself!



Working of GameCube

How GameCube Works


In the United States, the Nintendo GameCube is the undeniable underdog of the "console wars." Sony's PlayStation 2 and Microsoft's Xbox certainly sell better, and they tend to get more media attention. Toward the end of 2002, for example, the PlayStation 2 stirred up a lot of controversy with its new game Grand Theft Auto : Vice City, and Microsoft had a hit with Xbox Live, its online gaming program. Once the undisputed king of home video games, Nintendo seems to be struggling just to hold its own.





The GameCube comes in a variety of colors like its predecessor Nintendo 64.

But if you've actually spent any time with a GameCube, you may be confused by its reputation as a third-rate system. It's hard to see ground-breaking GameCube games like Metroid Prime and Super Mario Sunshine as anything less than state of the art. No matter how it fares in sales, this console is definitely a remarkable technological achievement.

we'll find out what the GameCube has under the hood, and we'll see how it stacks up to the competition.



Working of Cable Modems

How Cable Modems Work


cable modem

Motorola SURFboard modem


For millions of people, television brings news, entertainment and educational programs into their homes. Many people get their TV signal from cable television (CATV) because cable TV provides a clearer picture and more channels. (See How Cable TV Works for details.)

Many people who have cable TV can now get a high-speed connection to the Internet from their cable provider. Cable modems compete with technologies like asymmetrical subscriber lines (ADSL). If you have ever wondered what the differences between DSL and cable modems are, or if you have ever wondered how a computer network can share a cable with dozens of television channels, then read on. In this article, we'll look at how a cable modem works and see how 100 cable television channels and any Web site out there can flow over a single coaxial cable into your home.



Working of Xbox 360

How Xbox 360 Works

Microsoft's first video game console, the Xbox, has sold more than 20 million units worldwide since its introduction in 2001. Despite the Xbox's impressive power, the list of big-name video game titles to support it and the success of the Xbox's online component, Xbox LIVE, Sony's PlayStation 2 still outsold it.

As the game industry moved into the next generation of video game technology, Microsoft was determined to dethrone Sony's PlayStation. Enter the Xbox 360.



The Xbox 360.

Xbox 360.

Microsoft rebuilt the Xbox from the ground up. From the name to the look to hardware and features, the Xbox 360 is a radically different and more powerful machine than its predecessor. Far more than a video game console, the Xbox 360 is a total media center that allows users to play, network, rip, stream and download all types of media, including high-definition movies, music, digital pictures and game content.

In this article, we will learn about the hardware and features that make the Xbox 360 a leap forward into the next generation of gaming consoles.


The Xbox 360, like all video game consoles, is just a computer with hardware and software dedicated to the function of running video game software. The original Xbox was essentially a Windows PC with a modified Pentium III processor, some relatively powerful graphics and audio hardware and a modified version of the Microsoft operating system Windows 2000, all packaged in that distinctive black box. The Xbox 360 is also a specially packaged computer, but once you look inside, you realize that this console has quite a bit under the hood:

  • Custom IBM Power PC-based CPU with three 3.2 GHz cores
  • Custom ATI graphics processor with 10 MB embedded DRAM
  • 512 MB 700 MHz GDDR3 RAM
  • Detachable and upgradeable hard drive -- all models except the Core system
  • 12x dual-layer DVD-ROM
  • Support for up to four wireless game controllers
  • Three USB 2.0 ports
  • Two memory unit slots

As you can see, Microsoft intends the Xbox 360 to be a serious game machine. The company is also serious about reaching more audiences with the Xbox 360. On the next page, we'll look at variations of the Xbox 360 that are marketed to different kinds of gamers.



Monday, January 18, 2010

Working of Firefox

How Firefox Works

firefox logo
Firefox is an alternative browser to Opera, Safari, Internet Explorer and other Web browsers.

­A Web browser is sort of like the tires on your car. You don't really give them much daily thought, but without them, you're not going anywhere. The second something goes wrong, you definitely notice.

Chances are, you're reading this article on a version of Microsoft's Internet Explorer. It's the browser that comes already installed on computers with Windows operating systems; most people use Windows, and many Windows users don't give a second thought to which browser they're using. In fact, some people aren't aware that they have an option at all.

Options are out there, however, and one of them has been steadily chipping away at Internet Explorer's dominance. It's called Firefox. From its origins as an offshoot of the once-popular Netscape browser, Firefox is building a growing legion of dedicated users who spread their enthusiasm by word of mouth

For a while, it seemed like Microsoft's Internet Explorer was going to dominate the browser market indefinitely. Its competitors included Netscape Navigator and the AOL Browser -- and it soundly beat both of them. When Firefox debuted, it faced an uphill battle to claim space in the market. But Firefox's popularity has grown since its debut, particularly among Web administrators and developers.


­The word is spreading quickly. On June 17, 2008, Firefox held an event called Download Day as it unveiled the final build of Firefox 3. The goal for the event was to encourage people to download the new browser and establish a record for the most downloads of a single application within a 24-hour period. The event was a success -- Firefox 3 is now in the Guinness Book of World Records for the application receiving the most downloads in a single day: 8,002,530 to be exact [source: Spread Firefox].

In this article, we'll find out what makes Firefox different, what it can do and what effect an open-source browser might have on the Internet landscape.




Working of Internet Explorer 8

What's new with Internet Explorer 8?


IE 8 Welcome page

Users who downloaded the beta version of Internet Explorer received a thank you from Microsoft upon launching the new browser.

The World Wide Web is constantly evolving. The earliest Web pages were static sites that featured a few images, some text and the occasional unwelcome MIDI file. Today, Web sites may incorporate sophisticated elements such as Flash animation, video and customized markup languages. But you can't experience innovative features on the Web without a browser designed to handle everything the Web can offer.

That's why Microsoft released a beta version of Internet Explorer 8 (IE 8) in 2008. Beta versions are unfinished builds of programs. The purpose of a beta version is to allow people to test a product before its final build. This gives developers an opportunity to see which features become popular, which ones are ignored and which ones may need some tweaking before the final release. It also lets the developers test the stability of their program before launch. In January 2009, Microsoft offered consumers a release candidate version of the browser -- one step closer to the final official build of Internet Explorer 8.

It took five years for Internet Explorer 7 to hit the Web after the introduction of Internet Explorer 6. But the beta for Internet Explorer 8 appeared only two years after its predecessor. As the Internet and Web evolve, browser developers have to push to stay ahead -- or even keep up. That's just one reason IE 8 appeared so quickly on the heels of IE 7.


Another reason is that Microsoft is preparing Windows 7, the next version of the Windows operating system, for the market. Internet Explorer 7 harnessed the capabilities of the previous operating system: Windows Vista. But Vista suffered from bad press. It turns out the operating system had some problems when it went to market. Many journalists pointed out those problems and before long, people associated Vista with security issues and stability problems. Even though Microsoft released patches to address these early problems, the stigma remained.

Microsoft has designed Internet Explorer 8 to take advantage of some of the capabilities in Windows 7, much as IE 7 worked with Vista. But IE 8 will work on other operating systems as well. Let's take a closer look at the new browser.



Working of Windows Vista

How Windows Vista Works


The first version of Microsoft Windows hit the market in 1983. But unlike today's versions of Windows, Windows 1.0 was not an operating system (OS). It was a graphical user interface that worked with an existing OS called MS-DOS. Version 1.0 didn't look much like newer versions, either -- not even Windows 3.0, which many people think of as the first real version of Windows. Its graphics were simpler and used fewer colors than today's user interfaces, and its windows could not overlap.

Vista logo

Windows has changed considerably since then. In the last 20 years, Microsoft has released numerous full-fledged versions of the operating system. Sometimes, newer versions are significantly different from older ones, such as the change from Windows 3.1 to Windows 95. Other new releases have seemed more like enhancements or refinements of the older ones, such as the multiple consumer versions of the OS released from 1995 to 2001.

Microsoft's newest version of its operating system is Windows Vista. For many users, upgrading to Vista won't seem as dramatic as the upgrade from 3.1 to Windows 95. But Windows Vista has a number of new features, both in the parts that you can see and the parts that you can't.

At its core, Windows Vista is still an operating system. It has two primary behind-the-scenes jobs:

  • Managing hardware and software resources, including the processor, memory, storage and additional devices
  • Allowing programs to work with the computer's hardware

If all goes well, this work is usually invisible to the user, but it's essential to the computer's operation. You can learn about these tasks in more detail in How Operating Systems Work.

But when many people think of operating systems, they think of the portion they can see -- the graphical user interface (GUI). The GUI is what people use to interact with the hardware and software on the computer. In Windows systems, features like the Start menu, the recycle bin and the visual representations of files and folders are all part of the GUI.

Windows Vista's GUI is a 3-D interface called Windows Aero. Of the four editions of Windows Vista, three -- Home Premium, Business and Ultimate -- support Windows Aero. Home Basic, the most scaled-down edition of the OS, uses a less graphics-intensive GUI instead of Aero. The other editions can also use this basic GUI, so people with older computers that can't support lots of 3-D graphics can still upgrade to Vista.

We'll take a closer look at the Aero GUI and other Vista features next.

Microsoft's Web site has more information on which features each edition includes.

Additional Editions
In addition to the four primary editions of Windows Vista, there are two editions for special markets. Windows Vista Enterprise is designed for very large businesses. Windows Vista Starter is a basic Vista OS for use in emerging markets, such as developing countries.



Working of Microsoft

How Microsoft Works




Microsoft founder Bill Gates talks at the Sorbonne University in Paris. Gates has been a big supporter of microformats, saying they're needed for future innovation.

Microsoft founder Bill Gates has defined how we use computers

Microsoft is a software company. It makes money by selling its software for use on computers.

That's an accurate summary, but it doesn't tell anywhere near the whole story. It doesn't tell you that Microsoft is a business empire without equal, that its products are used in nearly every computer on the planet, or that it has yet to reach the height of its power and influence. Microsoft has become a symbol of all that is great about the information age, as well as all that is less-than-great about it.

Although you may find yourself cursing the "evil empire" when your system crashes, or when you spend money on another upgrade, Microsoft is unsurpassed when it comes to powering information technology. Whether by cunning, innovation, determination, or a mix of these qualities, Bill Gates' Microsoft has defined how we use computers since the first IBM PC rolled out in 1981 with Microsoft's MS-DOS in its innards.


­ So Microsoft rules the world, but just what does it do, anyway? In this article, we'll take a look at the history of Microsoft and find out how it competes in the market. We'll also explore how Microsoft's corporate culture factors into its success. Finally, we'll look at Microsoft products to find out how they benefit from the company's core advantages.



Working of Yahoo Messenger

How Yahoo Messenger Works


Without instant messaging through Yahoo Messenger and other services, teens would lose a vital social communications tool, and the rest of us wouldn't have an easy way to send and receive messages quickly from our computers or mobile phones.

yahoo messenger

Yahoo messenger allows friends to chat online.

While Yahoo Inc. wan't the first Internet service provider to offer free instant messaging, it is one of the Web's most popular IM services. Launched in 1999, Yahoo Messenger has more than an estimated 94 million users who use to exchange instant messages with other Yahoo, Microsoft Windows Live Messenger or Lotus Sametime users [sources: Time Warner and PC World].

Once you download Yahoo Messenger software and complete the Yahoo Messenger sign in, you'll find the service also does a lot more. You can, for example, access contacts and messages anywhere from any Web browser, communicate in any of 40 languages and share photos and large-file Web video.

Before we delve further into Yahoo Messenger, let's take a quick look at instant messaging. What exactly is it? Instant messaging allows you to carry on a conversation with someone else via your personal computer. You type in a message, which then travels in digital form over the Internet from your computer through the provider's server to the other person's computer. Within a few seconds, the message appears in an IM window on the recipient's computer screen. That person reads the message and types back a response. Small, separate IM windows on the screen allow you to carry on conversations with several different people at a time. For more information about instant messaging, check out How Instant Messaging Works.

When e-mail contact isn't fast or convenient enough, Internet users turn to IM. Many teens use IM daily to talk to five or six friends at a time while simultaneously listening to music, doing homework and talking on their cell phone.

Teens aren't the only group found IM handy. This communications tool also works for business colleagues checking details with sales reps on the road, friends trying to find a time to talk at length and mobile phone users who need to check in with the office or contact each other. The number of IM users worldwide was estimated at 461 million in 2007 and is expected to reach 711 million by 2011, according to the Radicati Group, a market research firm specializing in messaging and collaboration technologies.

Next, let's see how easy it's to get started with Yahoo Messenger.




Working of Yahoo Mail

How Yahoo Mail Works


A world without the convenience of e-mail is hard to imagine -- which may explain, in part, why millions of us have turned to Yahoo Mail and other free Web-based e-mail services for fast communications. While AOL, Prodigy and CompuServe came earlier, Yahoo Inc. entered the field with Yahoo Mail in 1997 and has become a leader with an estimated 250 million users worldwide [sources: Computerworld and search Engine Journal].

Yahoo mail

­Yahoo mail is one of the most popular free e-mail services.

No matter which e-mail service we use, many of us use it frequently. A March 2007 survey conducted by the Pew Internet and American Life Project indicated that 71 percent of U.S. adults use the Internet. Among those users, 91 percent send or read e-mail online, and 56 percent use e-mail every day. Looking at e-mails sent worldwide, technology research firm IDC estimated that nearly 97 billion e-mails would be sent daily in 2007 [source: IDC].

Check Yahoo Mail and what it offers, and you'll see a lot more than simply being able to send and receive e-mail messages. For starters, you can do that in 21 languages. A Yahoo Mail account also provides unlimited message storage, e-mail search, contact lists, personalization, spam blockers and virus scanning.

Launched in August 2007, the new version of Yahoo Mail allows users to choose how they want to communicate, switching among e-mail, chat and text-messaging options. This version also adds keyboard shortcuts, direct access through RSS (Really Simple Syndication) feeds to changing Web content and mobile access from Internet-equipped smartphones and PDAs.

In this article, we'll take a closer look at these and other features of Yahoo Mail and how to use them. First, let's see how easy setting up a Yahoo Mail account is.




Working of BlackBerrys

How a BlackBerry Works

When the BlackBerry debuted in 1999, carrying one was a hallmark of powerful executives and savvy technophiles. People who purchased one either needed or wanted constant access to e-mail, a calendar and a phone. The BlackBerry's manufacturer, Research in Motion (RIM), reported only 25,000 subscribers in that first year. But since then, its popularity has skyrocketed.

BlackBerry logo

In September 2005, RIM reported 3.65 million subscribers, and users describe being addicted to the devices. The BlackBerry has even brought new slang to the English language. There are words for flirting via BlackBerry (blirting), repetitive motion injuries from too much BlackBerry use (BlackBerry thumb) and unwisely using one's BlackBerry while intoxicated (drunk-Berrying). While some people credit the BlackBerry with letting them get out of the office and spend time with friends and family, others accuse them of allowing work to infiltrate every moment of free time.

In this article, we'll examine the "push" technology at the center of the device's popularity, RIM's former dispute with patent holder NTP Incorporated and its current dispute with Visto Corporation. We'll also explore BlackBerry hardware and software.

"Push" Technology

RIM Revenue
  • 1999: $47,342,000
  • 2005: $1,350,447,000
  • Source:

    2000 RIM Annual Report

A PDA does a lot of the same things a BlackBerry does, and the PDA made its
debut several years before the BlackBerry. But until recently, the only way to make the information on most PDAs match the
information on a person's computer was to automatically or manually sync the PDA. This could be time-consuming and inconvenient. It could also lead to exactly the conflicts that having a PDA is supposed to prevent. For example, a manager might schedule a meeting on the PDA, not knowing that an assistant had just scheduled a meeting for the same time on a networked calendar.

A BlackBerry, on the other hand, does everything a PDA can do, and it syncs itself continually through push technology. BlackBerry Enterprise Server or Desktop Redirector software "pushes," or redirects, new e-mail, calendar updates, documents and other data straight to the user over the Internet and the cell phone network.­

First, the software senses that a new message has arrived or the data has changed. Then, it compresses, packages and redirects the information to the handheld unit. The server uses hypertext transfer protocol (HTTP) and transmission control protocol (TCP) to communicate with the handhelds. It also encrypts the data with triple data encryption standard (DES) or advanced encryption standard (AES).

A woman using a BlackBerry

A person can send and receive messages and phone calls on a BlackBerry from virtually any location.

The software determines the capabilities of the BlackBerry and lets people establish criteria for the information they want to have delivered. The criteria can include message type and size, specific senders and updates to specific programs or databases.

Once all of the parameters have been set, the software waits for updated content. When a new message or other data arrives, the software formats the information for transmission to and display on the BlackBerry. It packages e-mail messages into a kind of electronic envelope so the user can decide whether to open or retrieve the rest of the message.

BlackBerry Devices in the United States
70 percent of BlackBerry subscribers live in the United States. Source: Washington post

The BlackBerry listens for new information and notifies the user when it arrives by vibrating, changing an icon on the screen or turning on a light. The BlackBerry does not poll the server to look for updates. It simply waits for the update to arrive and notifies the user when it does. With e-mail, a copy of each message also goes to the user's inbox on the computer, but the e-mail client can mark the message as read once the user reads it on the BlackBerry.

People describe BlackBerry use as an addiction, and this is why. Not only do they give people constant access to their phones, they also provide continual updates to e-mail, calendars and other tools.

Lately, RIM had been dealing with issues of patent infringement. We'll look at that next.




Working of Gmail

How Gmail Works


Since its early beginnings which date all the way back to 2004, Gmail has offered users innovative features such as a gigabyte of free storage, built-in search functions and message groupings.

These features have ensured Gmail's place as a top-rated e-mail provider. In October 2007, Gmail was estimated to be the third largest free e-mail service with 87 million users worldwide, based on data from comScore Media Metrix. Yahoo Mail led the way with approximately 262 million users followed by about 256 million users for second-place MSN Hotmail (now Windows Live e-mail) [source: TechNews World].

While AOL and Yahoo have offered Web-based mail since the 1990s, Gmail started as an internal e-mail service at Google Inc. Originally the service was offered by invitation to Google members in April 2004. In February 2007, Google offered Gmail to everyone [source: Google history].

gmail

Gmail is a popular free e-mail service powered by Goo­gle.

Since then, Google has expanded the e-mail service's features to include group chat with AIM (AOL Instant Messenger) users, Gmail for mobile devices, access to e-mail from other services like AOL or Yahoo Mail, virus scanning, spam control, shortcuts and more. Gmail also provides messaging in 40 languages and allows attachments up to 20 megabytes in size [source: Google history].

In this article, we'll take a closer look at these and other Gmail features. First, let's see how easy it is to set up an account and go through Gmail sign in.




Saturday, January 16, 2010

Working of Spam

How Spam Works


Most of us get spam every day. Some of us get a little, and some of us get a lot, but if you have an e-mail account it is always there. For example, this morning, here's one that came to my inbox:

Subject: Adobe

Suppose we tell you that you could really lose up to 82% of your unwanted body fat and keep it off in just a few months, would you be interested? We certainly hope so! Please visit our web site - Click here!

Obviously this is spam, yet it made it through the spam filters and I opened it because the subject line made it unknowable whether it was spam or not. ­

Spam is incredibly annoying, especially in large quantities. If you have a public e-mail address you can receive hundreds of spam messages for every legitimate message that arrives. Even with good filters, some of the spam makes it through. And filters can sometimes delete messages that you really do want to receive. Spam is free speech run amok. ­

­ Where does all of this spam e-mail (also known as "unsolicited commercial e-mail") come from? Why is there so much of it? Is there any way to stop it? In this article, we will answer these questions and many others as we take a dive into the sea of spam.

Spam is a huge problem for anyone who gets e-mail. According to Business Week magazine:

In a single day in May [2003], No. 1 Internet service provider AOL Time Warner (AOL ) blocked 2 billion spam messages -- 88 per subscriber -- from hitting its customers' e-mail accounts. Microsoft (MSFT), which operates No. 2 Internet service provider MSN plus e-mail service Hotmail, says it blocks an average of 2.4 billion spams per day. According to research firm Radicati Group in Palo Alto, Calif., spam is expected to account for 45% of the 10.9 trillion messages sent around the world in 2003.
One of the problems with spam, and the reason why there is so much of it, is that it is so easy to create. ­

You could easily become a spammer yourself. Let's say that you have a recipe from your grandmother for the best blueberry muffins ever created. A friend suggests that you sell the recipe for $5.

You decide that your friend might be on to something, so you send an e-mail to the 100 people in your personal e-mail address book with the subject line, "These Blueberry Muffins Have Been Described as Heaven -- You Can Have the Recipe for $5!" Your e-mail contains a link to your blueberry muffin Web site. As a result of your 100 e-mails, you get two orders and make $10.


­ "Wow!" you think, "It cost me nothing to send those 100 e-mails, and I made $10. If I sent 1,000 e-mails I could make $100. If I sent a million e-mails I could make $100,000! I wonder where I could get a million e-mail addresses..."

So, how could you get 1 million e-mail addresses? Read on to find out.




Working of Trojan Horses

How Trojan Horses Work



Trojan horse viruses can put your computer at risk and cause your system to slow down or crash. How are they let inside?

Trojan horse viruses can put your computer at risk and cause your system to slow down or crash. How are they let inside?

One of the most enduring stories of the Trojan War, the most important conflict in Greek mythology, is the tale of the Trojan horse. Trying to find a way into the city of Troy, the great warrior Odysseus ordered his men to build a massive wooden horse, one big enough for several Greek soldiers to fit in. Once the structure was finished, he and several other warriors climbed inside, while the rest of the Greeks sailed away from Troy. One man named Sinon, however, stayed behind in order to deceive the Trojans, convincing them that his fellow Greeks had betrayed him and fled from the city. The wooden horse, he told the Trojans, was safe and would bring them luck.

After some discussion over the matter, the Trojans agreed to wheel the horse through their gates, unknowingly giving the Greek enemy access to the city. After proclaiming victory and partying all night, the citizens of Troy went to sleep -- it was then that Odysseus and his men crept out of the Trojan horse and wreaked havoc on the city.


­Although you've probably heard of the Trojan horse from Greek mythology, chances are you've also heard of Trojan horses in reference to computers. Trojan horses are common but dangerous programs that hide within other seemingly harmless programs. They work the same way the ancient Trojan horse did: Once they're installed, the program will infect other files throughout your system and potentially wreak havoc on your computer. They can even send important information from your computer over the Internet to the developer of the virus. The developer can then essentially control your computer, slowing your system's activity or causing your machine to crash.

­Though they're not actually viruses, they're referred to as "Trojan horse viruses," "Trojan viruses," "Trojan horses" or just plain "Trojans." Regardless of what people call them, they all mean same thing. But what happened? How did you let this Trojan horse into your computer in the first place? And what can you do stop one from getting in?




Working of pishping

How Phishing Works




phishing graphic

Phishing is a common method of online identity theft and virus spreading.

Suppose you check your e-mail one day and find a message from your bank. You've gotten e-mail from them before, but this one seems suspicious, especially since it threatens to close your account if you don't reply immediately. What do you do?

This message and others like it are examples of phishing, a method of online identity theft. In addition to stealing personal and financial data, phishers can infect computers with viruses and convince people to participate unwittingly in money laundering.

Most people associate phishing with e-mail messages that spoof, or mimic, banks, credit card companies or other business like Amazon and eBay. These messages look authentic and attempt to get victims to reveal their personal information. But e-mail messages are only one small piece of a phishing scam.

­From beginning to end, the process involves:

  1. Planning. Phishers decide which business to target and determine how to get e-mail addresses for the customers of that business. They often use the same mass-mailing and address collection techniques as spammers.
  2. Setup. Once they know which business to spoof and who their victims are, phishers create methods for delivering the message and collecting the data. Most often, this involves e-mail addresses and a Web page.
  3. Attack. This is the step people are most familiar with -- the phisher sends a phony message that appears to be from a reputable source.
  4. Collection. Phishers record the information victims enter into Web pages or popup windows.
  5. Identity Theft and Fraud. The phishers use the information they've gathered to make illegal purchases or otherwise commit fraud. As many as a fourth of the victims never fully recover [Source: Information Week].

­If the phisher wants to coordinate another attack, he evaluates the successes and failures of the completed scam and begins the cycle again.

Phishing scams take advantages of software and security weaknesses on both the client and server sides. But even the most high-tech phishing scams work like old-fashioned con jobs, in which a hustler convinces his mark that he is reliable and trustworthy. Next, we'll look at the steps phishers take to convince victims that their messages are legitimate.




Working of Internet Cookies

How Internet Cookies Work



Internet cookies raise privacy concerns, although they can also make the Web easier to navigate.

Most Internet cookies are incredibly simple, but they are one of those things that have taken on a life of their own. Cookies started receiving tremendous media attention back in 2000 because of Internet privacy concerns, and the debate still rages.


On the other hand, cookies provide capabilities that make the Web much easier to navigate. The designers of almost every major site use them because they provide a better user experience and make it much easier to gather accurate information about the site's visitors.

In this article, we will take a look at the basic technology behind cookies, as well as some of the features they enable.



Cookie Basics

In April of 2000 I read an in-depth article on Internet privacy in a large, respected mewspaper, and that article contained a definition of cookies. Paraphrasing, the definition went like this:

    Cookies are programs that Web sites put on your hard disk. They sit on your computer gathering information about you and everything you do on the Internet, and whenever the Web site wants to it can download all of the information the cookie has collected. [wrong]

Definitions like that are fairly common in the press. The problem is, none of that information is correct. Cookies are not programs, and they cannot run like programs do. Therefore, they cannot gather any information on their own. Nor can they collect any personal information about you from your machine.

Here is a valid definition of a cookie: A cookie is a piece of text that a Web server can store on a user's hard disk. Cookies allow a Web site to store information on a user's machine and later retrieve it. The pieces of information are stored as name-value pairs.

For example, a Web site might generate a unique ID number for each visitor and store the ID number on each user's machine using a cookie file.

internet explorer logo­
­Internet Explorer and other browsers store cookies on your computer.

­ If you use Microsoft's Internet Explorer to browse the Web, you can see all of the cookies that are stored on your machine. The most common place for them to reside is in a directory called c:\windows\cookies. When I look in that directory on my machine, I find 165 files. Each file is a text file that contains name-value pairs, and there is one file for each Web site that has placed cookies on my machine.

You can see in the directory that each of these files is a simple, normal text file. You can see which Web site placed the file on your machine by looking at the file name (the information is also stored inside the file). You can open each file by clicking on it.

For example, I have visited goto.com, and the site has placed a cookie on my machine. The cookie file for goto.com contains the following information:



    UserID    A9A3BECE0563982D    www.goto.com/


Working of Spyware

How Spyware Works




spyware example

Spyware is malicious software that can hijack and cripple your computer. It has been known to masquerade as a prize-notification pop-up window, like the example above and is one method of online identity theft and virus spreading.

Has your computer ever become so slow that you can fix yourself a snack in the time it takes your word processor to open? Perhaps spyware is to blame.

Spyware is a category of computer programs that attach themselves to your operating system in nefarious ways. They can suck the life out of your computer's processing power. They're designed to track your Internet habits, nag you with unwanted sales offers or generate traffic for their host Web site. According to some estimates, more than 80 percent of all personal computers are infected with some kind of spyware [source: FaceTime Communications]. But before you chuck your computer out the window and move to a desert island, you might want to read on. In this article we'll explain how spyware gets installed on your computer, what it does there and how you can get rid of it.

Some people mistake spyware for a computer virus. A computer virus is a piece of code designed to replicate itself as many times as possible, spreading from one host computer to any other computers connected to it. It usually has a payload that may damage your personal files or even your operating system.

­ Spyware, on the other hand, generally isn't designed to damage your computer. Spyware is defined broadly as any program that gets into your computer without your permission and hides in the background while it makes unwanted changes to your user experience. The damage it does is more a by-product of its main mission, which is to serve you targeted advertisements or make your browser display certain sites or search results.

At present, most spyware targets only the Windows operating system. Some of the more notorious spyware threats include Trymedia, Nuvens, Estalive, Hotbar and New.Net.Domain.Plugin [source: CA].



How Your Computer Gets Spyware

Spyware usually ends up on your machine because of something you do, like clicking a button on a pop-up window, installing a software package or agreeing to add functionality to your Web browser. These applications often use trickery to get you to install them, from fake system alert messages to buttons that say "cancel" when they really install spyware.Here are some of the general ways in which spyware finds its way into your computer:
  • Piggybacked software installation - Some applications -- particularly peer-to-peer file-sharing clients -- will install spyware as a part of their standard installation procedure. If you don't read the installation list closely, you might not notice that you're getting more than the file-sharing application you want. This is especially true of the "free" versions that are advertised as alternatives to software you have to buy. As the old saying goes, there's no such thing as a free lunch.

While it officially claims otherwise, Kazaa has been known to include spyware in its download package.


Working of Computer Viruses

How Computer Viruses Work







desktop computer with skull

A virus can spell doom for your computer.

Strange as it may sound, the computer virus is something of an Information Age marvel. On one hand, viruses show us how vulnerable we are -- a properly engineered virus can have a devastating effect, disrupting productivity and doing billions of dollars in damages. On the other hand, they show us how sophisticated and interconnected human beings have become.

For example, experts estimate that the Mydoom worm infected approximately a quarter-million computers in a single day in January 2004. Back in March 1999, the melissa virus was so powerful that it forced Microsoft and a number of other very large companies to completely turn off their e-mail systems until the virus could be contained. The ILOVEYOU virus in 2000 had a similarly devastating effect. In January 2007, a worm called Storm appeared -- by October, experts believed up to 50 million computers were infected. That's pretty impressive when you consider that many viruses are incredibly simple.

­­

When you listen to the news, you hear about many different forms of electronic infection. The most common are:
  • Viruses - A virus is a small piece of software that piggybacks on real programs. For example, a virus might attach itself to a program such as a spreadsheet program. Each time the spreadsheet program runs, the virus runs, too, and it has the chance to reproduce (by attaching to other programs) or wreak havoc.
  • E-mail viruses - An e-mail virus travels as an attachment to e-mail messages, and usually replicates itself by automatically mailing itself to dozens of people in the victim's e-mail address book. Some e-mail viruses don't even require a double-click -- they launch when you view the infected message in the preview pane of your e-mail software [source: Johnson].
  • Trojan horses - A Trojan horse is simply a computer program. The program claims to do one thing (it may claim to be a game) but instead does damage when you run it (it may erase your hard disk). Trojan horses have no way to replicate automatically.
  • Worms - A worm is a small piece of software that uses computer networks and security holes to replicate itself. A copy of the worm scans the network for another machine that has a specific security hole. It copies itself to the new machine using the security hole, and then starts replicating from there, as well.

­In this article, we will discuss viruses -- both "traditional" viruses and e-mail viruses -- so that you can learn how they work and understand how to protect yourself.


Virus Origins

Computer viruses are called viruses because they share some of the traits of biological viruses. A computer virus passes from computer to computer like a biological virus passes from person to person.

Unlike a cell, a virus has no way to reproduce by itself. Instead, a biological virus must inject its DNA into a cell. The viral DNA then uses the cell's existing machinery to reproduce itself. In some cases, the cell fills with new viral particles until it bursts, releasing the virus. In other cases, the new virus particles bud off the cell one at a time, and the cell remains alive.

Patch Tuesday
On the second Tuesday of every month, Microsoft releases a list of known vulnerabilities in the Windows operating system. The company issues patches for those security holes at the same time, which is why the day is known as "Patch Tuesday." Viruses written and launched on Patch Tuesday to hit unpatched systems are known as "zero-day" attacks. Thankfully, the major anti-virus vendors work with Microsoft to identify holes ahead of time, so if you keep your software up to date and patch your system promptly, you shouldn't have to worry about zero-day problems.


Working of Firewalls

How Firewalls Work


If you have been using the Internet for any length of time, and especially if you work at a larger company and browse the Web while you are at work, you have probably heard the term firewall used. For example, you often hear people in companies say things like, "I can't use that site because they won't let it through the firewall."

If you have a fast Internet connection into your home (either a DSL connection or a cable modem), you may have found yourself hearing about firewalls for your home network as well. It turns out that a small home network has many of the same security issues that a large corporate network does. You can use a firewall to protect your home network and family from offensive Web sites and potential hackers.

Basically, a firewall is a barrier to keep destructive forces away from your property. In fact, that's why its called a firewall. Its job is similar to a physical firewall that keeps a fire from spreading from one area to the next. As you read through this article, you will learn more about firewalls, how they work and what kinds of threats they can protect you from.



What Firewall Software Does

A firewall is simply a program or hardware device that filters the information coming through the Internet connection into your private network or computer system. If an incoming packet of information is flagged by the filters, it is not allowed through.

If you have read the article How Web Servers Work, then you know a good bit about how data moves on the Internet, and you can easily see how a firewall helps protect computers inside a large company. Let's say that you work at a company with 500 employees. The company will therefore have hundreds of computers that all have network cards connecting them together. In addition, the company will have one or more connections to the Internet through something like T1 or T3 lines. Without a firewall in place, all of those hundreds of computers are directly accessible to anyone on the Internet. A person who knows what he or she is doing can probe those computers, try to make FTP connections to them, try to make telnet connections to them and so on. If one employee makes a mistake and leaves a security hole, hackers can get to the machine and exploit the hole.

With a firewall in place, the landscape is much different. A company will place a firewall at every connection to the Internet (for example, at every T1 line coming into the company). The firewall can implement security rules. For example, one of the security rules inside the company might be:

    Out of the 500 computers inside this company, only one of them is permitted to receive public FTP traffic. Allow FTP connections only to that one computer and prevent them on all others.


Working of WiFi

How WiFi Works


If you've been in an airport, coffee shop, library or hotel recently, chances are you've been right in the middle of a wireless network. Many people also use wireless networking, also called WiFi or 802.11 networking, to connect their computers at hame, and some cities are trying to use the technology to provide free or low-cost Internet access to residents. In the near future, wireless networking may become so widespread that you can access the Internet just about anywhere at any time, without using wires.

One wireless router can allow multiple devices to connect to the Internet.
One wireless router can allow multiple devices to connect to the Internet.

WiFi has a lot of advantages. Wireless networks are easy to set up and inexpensive. They're also unobtrusive -- unless you're on the lookout for a place to use your laptop, you may not even notice when you're in a hotspot. In this article, we'll look at the technology that allows information to travel over the air. We'll also review what it takes to create a wireless network in your home.

First, let's go over a few WiFi basics.


What Is WiFi?

What's in a name?
You may be wondering why people refer to WiFi as 802.11 networking. The 802.11 designation comes from the IEEE. The IEEE sets standards for a range of technological protocols, and it uses a numbering system to classify these standards.

A wireless network uses radio waves, just like cell phones, television and radios do. In fact, communication across a wireless network is a lot like two-way radio communication. Here's what happens:

  1. A computer's wireless adapter translates data into a radio signal and transmits it using an antenna.
  2. A wireless router receives the signal and decodes it. The router sends the information to the Internet using a physical, wired Ethernet connection.


Friday, January 15, 2010

Working of iPod Hacks

How iPod Hacks Work




iPod with Linux

Linux on the iPod.

Right out of the box, an iPod can hold, organize and play most people's entire music collection. It can also act like a calendar and a clock, and newer models can play videos and a few simple games. But some people want more from their iPods.

Intrepid technophiles have found ways to hack iPods, giving them the ability to do much more than play music. In this article, we'll explore why iPods can be hacked, which hacks are our favorites and where to go to learn more.

We'll start by looking at what it means to hack an iPod. An iPod is a lot like a tiny computer. A fifth-generation (5g) iPod Video has:

  • A screen
  • A hard drive
  • A processor
  • Memory,including ROM and RAM
  • Video and audio chips
  • An input device (a click wheel)
  • A power source (a rechargeable battery)

A motherboard connects all of these components together, and external ports provide a place to connect a power cable, headphones and accessories. An iPod also has an operating system and software that allow it to read, store and access files. Firmware - software that tells the iPod how to behave and how to communicate with its software - resides in the device's read-only memory.

These components are like smaller versions of what you can find inside a computer or a laptop. But apart from size, there's one big difference between an iPod and a computer. When you buy a computer, you can also buy software and hardware to upgrade its capabilities. In some ways, computers even encourage you to do this. They have cases that you can open with simple tools and CD-ROM or disk drives that let you install software that you buy at the store. With an Internet connection, you can also legally purchase and download software from the Web.

­


An iPod, on the other hand, is a closed system. You can't get inside it without a special tool to pry the front and rear portions of the case apart. You can't go to a computer store and buy new iPod software. Just about anything you do to modify your iPod voids its warranty. For these reasons, modifications to an iPod's inner workings are known as hacks. When you hack an iPod, you're changing its hardware, software, firmware or operating system, something you're technically not supposed to do.

Numerous iPod hacks rely on one fundamental change - the addition of the open-source operating system Linux. The iPodLinux Project has worked out how to port Linux to an iPod and has developed a Linux user interface called podzilla. Installing Linux allows an iPod to play musical files that it does not normally support, like Ogg files. You can also download:

  • Schemes, which change the appearance of podzilla
  • Modules, which are essentially applications for use with the iPodLinux operating system
With the addition of Linux, an iPod becomes less like an MP3 player and more like a PDA or handheld computer.
Warning: Some Cars Not for Use with Some Sets
There's one important thing to keep in mind if you're thinking about hacking your iPod. Most hacks will void your warranty. In other words, if you decide to change your iPod's hardware or software, the folks at your local Apple Store's Genius Bar won't be able to help you if something goes wrong. In addition, some hacks only work with specific iPod models - a hack meant for a third-generation device might cause problems for a later model.

­ Currently, iPodLinux has been tested on first-, second- and third-generation iPods. Some users who have developed hacks for newer iPods report that it also works on fourth- and fifth-generation models. But regardless of whether it has been tested, installing Linux on an iPod unquestionably voids its warranty.

Getting your iPod to run Linux is really the ultimate hack. It's the foundation for using your iPod in an entirely new way, and it opens the door for limitless applications. For a lot of users, the addition of Linux adds enough options for applications and functions that the benefits outweigh the inherent risks of tampering with the iPod's programming.




Working of iPod Shuffle

How the iPod Shuffle Works


Some iPod owners can be very picky. They like listening to their albums from beginning to end. Any skipping around from one track to another will ruin the experience and force the listener to start over or give up altogether. They may spend hours organizing their iTunes library, making sure everything is in perfect order.



The latest iPod Shuffle, about the same size as a quarter, is Apple's budget model MP3 player.

The latest iPod Shuffle, about the same size as a quarter, is Apple's budget model MP3 player.

Many others aren't so fussy. A simple playlist, filled with randomly chosen songs and uploaded in seconds, will suffice for a morning run. Even better is the shuffle feature, which is designed to randomly select the songs from your iPod or iTunes library and play them back in whatever order they come. It's like a nice surprise at the end of each song -- your very own personal radio station that plays everything you like because, well, it's your music.

The first-generation iPod Shuffle, which looks (and acts) a lot like a memory stick.

The first-generation iPod Shuffle, which looks (and acts) a lot like a memory stick.­

Apple must have realized that many people enjoyed the shuffle function on their iPods, and the company tapped into the pleasure of the unexpected in 2005 by introducing the appropriately named iPod Shuffle. It's the budget model in Apple's iPod lineup, designed to take songs from a listener's library and play them back randomly.

The Shuffle isn't just the cheapest iPod; it's also the smallest. The first generation of the iPod Shuffle was about the size of a pack of gum and very similar in appearance to a memory stick -- indeed, after removing one end of the stick, the Shuffle could be inserted into a computer's USB drive and updated quickly. With no display and only five buttons, it held either 512 MB or 1 GB of music, and the smaller model was the first iPod less than $100.

The latest version of the iPod Shuffle is even smaller. It weighs only 0.55 ounces (15.6 grams), is 1.07 inches high and 1.62 inches wide and is only 0.41 inches thick. It's marketed by Apple as "wearable," since it's built with a clip on the back so listeners can wear on sleeves, collars or belts. Two models are available -- 1-GB models that hold 240 songs and cost $49, and 2-GB models that hold 500 songs and cost $69.

So how does an iPod Shuffle work? What does it look like on the inside? And just how random is iTunes? Shuffle over to the next page to find out.­


Working of iPods

How iPods Work


The sixth-generation iPod Classic

The sixth-generation iPod Classic.

In 2001, Apple introduced the iPod, an MP3 player with the unheard-of storage capacity of 5 gigabytes. Six iPod generations later, the iPod plays songs, movies, games and photo slideshows, and you can store up to 160 GB of any type of file you want. The evolution has been a lesson in consumer electronics marketing and development: Millions of people are so hooked on the iPod, they continue to buy it and its coordinating Apple products despite quick battery death and difficult repairs.

The 2007 iPod release, the sixth-generation iPod classic, is a digital audio player, video player, photo viewer and portable hard drive, making it a full-fledged portable media center. It's available in 80-GB and 160-GB capacities and has a color LCD screen. In addition to the iPod classic, there are several other devices in the current generation of iPod players:

  • iPod touch, announced in September 2007, is a touch-screen iPod with an 8-GB or 16-GB capacity. It looks a lot like an iPhone, and it uses the iPhone's multi-touch user interface. You can learn all about the technology in How the iPhone Works.
  • iPod shuffle, with a 1-GB capacity, plays only songs and has no display.
  • iPod nano plays digital audio, displays digital photos and comes in 4- and 8-GB capacities. It has a 2-inch display screen and a smaller form factor than the iPod video.

ipod nano

The newer iPod nano model has a larger screen.


In this article, we'll be focusing on iPods with audio and video capabilities. We'll dissect a fifth-generation iPod video to find out how it works, check out what type of software is available to enhance its functionality, and find out why so many people buy iPod after iPod.


iPod Basics

iPod Myths
  • If I use iPod as my digital-media player, I can only download music from the iTunes Store.
    Not true. You can download music from other sites (as long as the site doesn't use Windows Media DRM -- iPod isn't compatible with that encoding).

  • If I use iPod as my digital-media player, I can only use the iTunes software as my jukebox.
    Not true. While iPod is made to work with the iTunes software, there are other jukeboxes out there that you can use with your iPod.

  • If I download MP3 or WAV files to my iPod, they'll be converted into a proprietary audio format.
    Not true. Downloading files to an iPod doesn't change the format. iPod can play MP3, WAV, AAC, AIFF, Apple Lossless and Audible audio files.


Working of MP3 Players

How MP3 Players Work



ipod

The second generation iPod shuffle measures
1.07 by 1.62
inches and weighs less than one ounce.

The MP3 player is the most recent in an evolution of music formats that have helped consumers enjoy their tunes. Records, 8-track tapes, cassette tapes and CDs -- none of these earlier music formats provide the convenience and control that MP3 players deliver. With an MP3 player in hand or pocket, a consumer can create personalized music lists and carry thousands of songs wherever
they go.

All of that stored music and the MP3 player itself fit into a device that, in some cases, weighs less than one ounce. Portability is a large factor in the popularity of the MP3, considering the ease of transportation in comparison to a CD player and CD storage case. In addition, some devices provide additional technology, like video and photo viewing, alarm and calendar functions, and even cell phone and Internet service.­


­In this article, you'll learn more about the technology inside MP3 players and the diff­erent types of players available. You'll also find out how to get tunes and how you can accessorize your player. Get started by learning about the MP3 file format .


The MP3 File Format

The MP3 file format revolutionized music distribution in the late 1990s, when file-swapping services and the first portable MP3 players made their debut. MP3, or MPEG Audio Layer III, is one method for compressing audio files. MPEG is the acronym for Moving Picture Experts Group, a group that has developed compression systems for video data, including that for DVD movies, HDTV broadcasts and digital satellite systems.



Using the MP3 compression system reduces the number of bytes in a song, while retaining sound that is near CD-quality. Anytime you compress a song, you will lose some of its quality, which is the trade-off for the ability to carry more music files in a smaller storage system. A smaller file size also allows the song to be downloaded from the Internet faster.

Consider that an average song is about four minutes long. On a CD, that song uses about 40 megabytes (MB), but uses only 4 MB if compressed through the MP3 format. On average, 64 MB of storage space equals an hour of music. A music listener who has an MP3 player with 1 GB (approximately 1,000 MB) of storage space can carry about 240 songs or the equivalent of about 20 CDs. Songs stored on traditional CDs are already decompressed, so it takes more CDs to store the same amount of songs. (Some CDs support MP3 files.)

Although MP3 is perhaps the most well-known file format, there are other file formats that can be played on MP3 players. While most MP3 players can support multiple formats, not all players support the same formats. Here are a few of the file formats that can be played on different players:

  • WMA - Windows Media Audio
  • WAV - Waveform Audio
  • MIDI - Music Instrument Digital Interface.
  • AAC - Advanced Audio Coding
  • Ogg Vorbis - A free, open and un-patented music format
  • ADPCM - Adaptive Differential Pulse Code Modulation
  • ASF - Advanced Streaming Format
  • VQF - Vector Quantization Format
  • ATRAC - Sony's Adaptive Transform Acoustic Coding 3

In the next section, we'll look at the technology behind the player that allows you to listen to your music.