Camera

A digital camera (also digicam or camera for short) is a camera that takes video or still photographs, or both, digitally by recording images via an electronic image sensor.
Many compact digital still cameras can record sound and moving video as well as still photographs. In the Western market, digital cameras outsell their 35 mm film counterparts.
Digital cameras can do things film cameras cannot: displaying images on a screen immediately after they are recorded, storing thousands of images on a single small memory device, recording video with sound, and deleting images to free storage space. Some can crop pictures and perform other elementary image editing. Fundamentally they operate in the same manner as film cameras, typically using a lens with a variable diaphragm to focus light onto an image pickup device. The combination of the diaphragm and a shutter mechanism is used to admit the correct amount of light to the imager, just as with film; the only difference is that the image pickup device is electronic rather than chemical.
Digital cameras are incorporated into many devices ranging from PDAs and mobile phones (called camera phones) to vehicles. The Hubble Space Telescope and other astronomical devices are essentially specialised digital cameras.

Compact cameras are designed to be small and portable and are particularly suitable for casual and "snapshot" use, thus are also called point-and-shoot camera. The smallest, generally less than 20 mm thick, are described as subcompacts or "ultra-compacts". Compact cameras are usually designed to be easy to use, sacrificing advanced features and picture quality for compactness and simplicity; images can usually only be stored using lossy compression (JPEG). Most have a built-in flash usually of low power, sufficient for nearby subjects. Live preview is almost always used to frame the photo. They may have limited motion picture capability. Compacts often have macro capability, but if they have zoom capability the range is usually less than for bridge and DSLR cameras. Generally a contrast-detect autofocus system, using the image data from the live preview feed off the main imager, focuses the lens.
Typically, these cameras incorporate a nearly-silent leaf shutter into their lenses.To enable lower costs and smaller size, these cameras typically use image sensors with a diagonal of approximately 6 mm, corresponding to a crop factor around 6. This gives them weaker low-light performance, greater depth of field, generally closer focusing ability, and smaller components than cameras using larger sensors.

MP3

Digital sampling is used to convert an audio wave to a sequence of binary numbers that can be stored in a digital format, such as MP3. Common features of all MP3 players are a memory storage device, such as flash memory or a miniature hard disk drive, an embedded processor, and an audio codec microchip to convert the compressed file into an analogue sound signal.Most DAPs are powered by rechargeable batteries, some of which are not user-replaceable. They have a 3.5 mm stereo jack; music can be listened to with earbuds or headphones, or played via an external amplifier. Some devices also contain internal speakers, through which music can be listened to, although these built-in speakers are typically of very low quality.
Nearly all DAPs consists of some kind of display screen, although there are exceptions, such as the iPod Shuffle, and a set of controls with which the user can browse through the library of music contained in the device, select a track, and play it back. The display, if the unit even has one, can be anything from a simple one or two line monochrome LCD display, similar to what are found on typical calculators, to large full-color displays capable of displaying photographs or viewing video content on. The controls can range anywhere from the simple buttons as are found on most typical CD players, such as for skipping through tracks or stopping/starting playback to full touch-screen controls, such as that found on the iPod Touch or the Zune HD. One of the more common methods of control is some type of the scroll wheel with associated buttons. This method of control was first introduced with the Apple iPod and many other manufacturers have created variants of this control scheme for their respective devices.
Content is placed on DAPs typically through a process called "syncing", by connecting the device to a personal computer, typically via USB, and running any special software that is often provided with the DAP on an enclosed CD-ROM, or downloaded from the manufacturer's website. Some devices simply appear as an additional disk drive on the host computer, to which music files are simply copied like any other type of file. Other devices, most notably the Apple iPod or Microsoft Zune, requires the use of special management software, such as iTunes or Zune Software. The music, or other content such as TV episodes or movies, is added to the software to create a "library". The library is then "synced" to the DAP via the software. The software typically provides options for managing situations when the library is to large to fit on the device being synced to. Such options include allowing manual syncing, in that the user most manually "drag-n-drop" the desired tracks to the device, or allow for the creation of playlists. Some of the more advanced units are now starting to allow syncing through a wireless connection, such as via WiFi or Bluetooth.
Content can also be obtained and placed on some DAPs, such as the iPod Touch or Zune HD by allowing access to a "store" or "marketplace", most notably the iTunes Store or Zune Marketplace, from which content, such as music and video, and even games, can be purchased and downloaded directly to the device.

USB

A USB flash drive consists of flash memory data storage device integrated with a USB (Universal Serial Bus) 1.1 or 2.0 interface. USB flash drives are typically removable and rewritable, much smaller than a floppy disk, and most weigh less than 30 g . Storage capacities in 2009 can be as large as 256 GB with steady improvements in size and price per capacity. Some allow 1 million write or erase cycles and have a 10-year data retention cycle.
USB flash drives are often used for the same purposes as floppy disks were. They are smaller, faster, have thousands of times more capacity, and are more durable and reliable because of their lack of moving parts. Until approximately 2005, most desktop and laptop computers were supplied with floppy disc drives, but most recent equipment has abandoned floppy disk drives in favor of USB ports.
Flash drives use the USB mass storage standard, supported natively by modern operating systems such as Windows, Linux, and other Unix-like systems. USB drives with USB 2.0 support can store more data and transfer faster than a much larger optical disc drive and can be read by most other systems such as the Playstation .
Nothing moves mechanically in a flash drive; the term drive persists because computers read and write flash-drive data using the same system commands as for a mechanical disk drive, with the storage appearing to the computer operating system and user interface as just another drive. Flash drives are very robust mechanically, and can withstand anything that does not actually break the circuit board or connector.
A flash drive consists of a small printed circuit board carrying the circuit elements and a USB connector, insulated electrically and protected inside a plastic, metal, or rubberized case which can be carried in a pocket or on a key chain, for example. The USB connector may be protected by a removable cap or by retracting into the body of the drive, although it is not likely to be damaged if unprotected. Most flash drives use a standard type-A USB connection allowing plugging into a port on a personal computer, but drives for other interfaces also exist.
Advantage of using USB, it helps to store the data for futher. It helps to transfer the data from one computer to another computer.Disadvantage of using, USB data may be lost while carrying from one place to another place.USB may be damaged by water.

MP4

MPEG-4 is a patented collection of method defining compression of audio and visual (AV) digital data. It was introduced in late 1998 abs designated a standard for a group of audio and video coding formats and related technology agreed upon by the ISO Moving picture Experts Groups under the formal standard ISO14496-coding of audio-visual objects.Uses of MPEG-4 include compression of AV data for web (streaming media) and CD distribution, voice(telephone, videophone) and broadcast television application.

MPEG-4 absorbs many of the features of MPEG-1 and MPEG-2 and other related standards, adding new features such as (extended) VRML support for 3Drendering, object-oriented composite files(including audio, video and VRML objects), support for externally speckfied Digital Rights Management and various types of interactivity. AAC (Advanced Audio Coding) was standardized as an adjunct to MPEG-2 before MPEG-4 was issued.

MPEG-4 is still a developing standard and is divided into a number of parts.Companies promoting MPEG-4 compatibility do not always clearly state which "parts level compatibility they are referring to. The key parts to be aware of are MPEG-4 part 2 and MPEG-4 part 10.

Most of the features included in MPEG-4 are left to individual developer to decide whether to implement them. This means that there are probably mo complete implementations of the entire MPEG-4 Ste of standards. To deal with this,that standard includes the concept of "profiles" and "leaves" , allowing a specific set of capabilities to be defined in a manner appropriate for a subset of applications.

Initially, MPEG-4 was aimed primarily at low bit-rate video communications;however, its scopes as a multimedia coding standard was later expanded. MPEG-4 is efficient across a variety of bit-rates ranging from a few kilobits per second to tens of megabits per second.

ipod

The ipod line came from Apple's "digital hub" category, when the company began creating software for the growing market of personal digital devices. Digital cameras, camcorders and organizer had well-established mainstream markets, but the company found existing digital music players "big and clunky or small and useless" with user interfaces that were "unbelievably awayful,"so Apple decide to develop its own. The product was developed in less than one year and unveiled on 23 October 2001. Jobs announced it as a Mac-compatible produced with a 5 GB hard drive that put"1,000 songs in your pock. Apple did not develop the ipod software entirely in-house, instead using portal player's reference plate form based on two ARM cores. The platform had rudimentary software running on a commercial micro kernel embedded operating system.

Portal player had previously been working on an IBM-brocaded MP3 player with Blue tooth headphones.Apple contracted another company, Piox, to help design and implement the user interface. As development progressed, Apple continued to define the software's look and feel. Starting with the ipod Mini, the Chicago font was replaced with Espy Sans. Later ipods switched forts again to podium Sans a font similar to Apple's corporate font, Myriad. ipods with color displays then adopted some Mac OS X themes like Aqua progress bars, and bushed metal meant to evoke a combination lock.In 2007 Apple modified the ipod interface against with the introduction of the sixth-generation ipod classic and third-generation ipod Nano by changing the font to Helvetica and, in most cases, splitting the screen in half by displaying the menus on the left and album artwork, photos, or videos on the right.

In September 2007 during the course of a lawsuit with patent holding company.Apple drew attention to patent for a similar device that was developed in 1979.Kane Kramer patented the idea of a "plastic music box" in 1979,which he called the IX.He was unable to secure funding to renew the worldwide patent, so it lapsed and Kramer never profited from his idea.

Telephone

A traditional landline telephone system, also known as "plain old telephone service" (POTS), commonly handles both signaling and audio information on the same twisted pair of insulated wires the telephone line. Although originally designed for voice communication, the system has been adapted for data communication such as Telex, Fax and Internet communication. The signaling equipment consists of a bell, beeper, light or other device to alert the user to incoming calls, and number buttons or a rotary dial to enter a telephone number for outgoing calls. A twisted pair line is preferred as it is more effective at rejecting electromagnetic interference (EMI) and crosstalk than an untwisted pair.
The telephone consists of an alerting device, usually a ringer, that remains connected to the phone line whenever the phone is "on hook", and other components which are connected when the phone is "off hook". These include a transmitter (microphone), a receiver (speaker) and other circuits for dialing, filtering, and amplification. A calling party wishing to speak to another party will pick up the telephone's handset, thus operating a button switch or "switchhook", which puts the telephone into an active (off hook) state by connecting the transmitter (microphone), receiver (speaker) and related audio components to the line. This circuitry has a low resistance (less than 300 Ohms) which causes DC current (48 volts, nominal) from the telephone exchange to flow through the line. The exchange detects this DC current, attaches a digit receiver circuit to the line, and sends a dial tone to indicate readiness. On a
modern telephone, the calling party then presses the number buttons in a sequence corresponding to the telephone number of the called party. The buttons are connected to a tone generator circuit that produces DTMF tones which end up at a circuit at the exchange. A rotary dial telephone employs pulse dialing, sending electrical pulses corresponding to the telephone number to the exchange. (Most exchanges are still equipped to handle pulse dialing.) Provided the called party's line is not already active or "busy", the exchange sends an intermittent ringing signal (about 90 volts AC in North America and UK and 60 volts in Germany) to alert the called party to an incoming call.If the called party's line is active, the exchange sends a busy signal to the calling party. However, if the called party's line is active but has call waiting installed, the exchange sends an intermittent audible tone to the called party to indicate an incoming call.
The phone's ringer is connected to the line through a capacitor, a device which blocks the flow of DC current but permits AC current. This constitutes a mechanism whereby the phone draws no current when it is on hook, but exchange circuitry can send an AC voltage down the line to activate the ringer for an incoming call. When a landline phone is inactive or "on hook", the circuitry at the telephone exchange detects the absence of DC current flow and therefore "knows" that the phone is on hook with only the alerting device electrically connected to the line. When a party initiates a call to this line, and the ringing signal is transmitted. When the called party picks up the handset, they actuate a double-circuit switchhook which simultaneously disconnects the alerting device and connects the audio circuitry to the line. This, in turn, draws DC current through the line, confirming that the called phone is now active.
The exchange circuitry turns off the ring signal, and both phones are now active and connected through the exchange. The parties may now converse as long as both phones remain off hook. When a party "hangs up", placing the handset back on the cradle or hook, DC current ceases to flow in that line, signaling the exchange to disconnect the call.
Calls to parties beyond the local exchange are carried over "trunk" lines which establish connections between exchanges. In modern telephone networks, fiber-optic cable and digital technology are often employed in such connections. Satellite technology may be used for communication over very long distances.

Computer

The first use of the word "computer " was recorded in 1613, peferring to a person who carried out calculations, or computations, and the word continued to be used in that sense until the middle of the 20th century. From the end of the 19th century onwards though, the word began to take on its more familiar meaning, describing a machine that carries out cpmputations.

The history of the modern computer begins with two separate technologies-automated calculation and programmability but no single device can be identified as the rarliest computer, partly because of the inconsistent application of that term. Examples of rarly mechanical calculating fevices include the abacus, the slide ruke and arguably the astrolabe and the Antikythera mechanism. Hero of Alexandria built a mechanical theater which performed a play listing 10 minutes and was operated by a complex system of ropes and drums that might be considered to be a means of deciding which parts of the mechanism performed which actions ans when. This is the essence of programmability.

The "castle clock", an astronomical clock invented by Al-jazari in 1206, is considered to be the earliest programmable analot computer. It displayed the zodiac, the solar and lunar orbits, a crescent moon-shaped pointer travelling acress a gateway causing automatic doors to open every hour, and five ronotic musicians who played music when struck by levers operated by a camshaft attached to a wate wheel. The length of day and night could be re-programmed to compensate for the changing lengths of day and night throughout the year.

In 1801, Joseph Marie Jacquard made an improvement to the textile loom by introducing a series of punched paper cards as a templates which allowed his loom to weave intricate the use of punched cards to define woven patterns can be viewed as an early,albeit limited, form of programmability.

It was the fusion of automatic calculation with programmability that produced the first recognizable computers.In1837, charles Babbage was the first to conceptualize and design a fully programmable mechanical computer, his analytical engine.Linited finances and Babbage's inability to resist tinkering with the design meant that the device was never completed.