Universal Serial Bus (USB)

Very popular communication port today, these use in every tools and gadget. Such as mobile phone , pocket PC , Card Reader , Printer , External HD , etc. That’s nature . because these communication port is very simple in use and give a lot of benefit then other.

So , i think we have to know why USB is very popular and what makes these thing very powerful. To know more let’s take a look bellow.

In information technology, Universal Serial Bus (USB) is a serial bus standard to interface devices to a host computer. USB was designed to allow many peripherals to be connected using a single standardized interface socket and to improve the plug-and-play capabilities by allowing hot swapping, that is, by allowing devices to be connected and disconnected without rebooting the computer or turning off the device. Other convenient features include providing power to low-consumption devices without the need for an external power supply and allowing many devices to be used without requiring manufacturer specific, individual device drivers to be installed.

USB is intended to replace many legacy varieties of serial and parallel ports. USB can connect computer peripherals such as mouse, keyboards, PDAs, gamepads and joysticks, scanners, digital cameras, printers, personal media players, and flash drives. For many of those devices USB has become the standard connection method. USB was originally designed for personal computers, but it has become commonplace on other devices such as PDAs and video game consoles, and as a bridging power cord between a device and an AC adapter plugged into a wall plug for charging purposes. As of 2008, there are about 2 billion USB devices in the world.

The design of USB is standardized by the USB Implementers Forum (USB-IF), an industry standards body incorporating leading companies from the computer and electronics industries. Notable members have included Agere (now merged with LSI Corporation), Apple Inc., Hewlett-Packard, Intel, NEC, and Microsoft.

The USB 1.0 specification model was introduced in November 1995. USB was created by the core group of companies that consisted of Intel, Compaq, Microsoft, Digital, IBM, and Northern Telecom. Intel produced the UHCI host controller and open software stack; Microsoft produced a USB software stack for Windows and co-authored the OHCI host controller specification with National Semiconductor and Compaq; Philips produced early USB-Audio; and TI produced the most widely used hub chips. Originally USB was intended to replace the multitude of connectors at the back of PCs, as well as to simplify software configuration of communication devices.

The original Apple "Bondi blue" iMac G3, introduced May 6, 1998, was the first computer to offer USB ports without offering "legacy" ports USB 1.1 came out in September 1998 to help rectify the adoption problems that occurred with earlier iterations of USB, mostly those relating to hubs

As of 2008, the USB specification is at version 2.0 (with revisions). Hewlett-Packard, Intel, Lucent (now LSI Corporation since its merger with Lucent spinoff Agere Systems), Microsoft, NEC, and Philips jointly led the initiative to develop a higher data transfer rate than the 1.1 specification. The USB 2.0 specification was released in April 2000 and was standardized by the USB-IF at the end of 2001. Equipment conforming with any version of the standard will also work with devices designed to any previous specification (known as backward compatibility).

A USB system has an asymmetric design, consisting of a host, a multitude of downstream USB ports, and multiple peripheral devices connected in a tiered-star topology. Additional USB hubs may be included in the tiers, allowing branching into a tree structure with up to five tier levels. A USB host may have multiple host controllers and each host controller may provide one or more USB ports. Up to 127 devices, including the hub devices, may be connected to a single host controller.

USB devices are linked in series through hubs. There always exists one hub known as the root hub, which is built in to the host controller. So-called "sharing hubs", which allow multiple computers to access the same peripheral device(s), also exist and work by switching access between PCs, either automatically or manually. They are popular in small-office environments. In network terms, they converge rather than diverge branches.

A physical USB device may consist of several logical sub-devices that are referred to as device functions. A single device may provide several functions, for example, a webcam (video device function) with a built-in microphone (audio device function).

USB device communication is based on pipes (logical channels). Pipes are connections from the host controller to a logical entity on the device named an endpoint. The term endpoint is occasionally used to incorrectly refer to the pipe. A USB device can have up to 32 active pipes, 16 into the host controller and 16 out of the controller.

Each endpoint can transfer data in one direction only, either into or out of the device, so each pipe is uni-directional. Endpoints are grouped into interfaces and each interface is associated with a single device function. An exception to this is endpoint zero, which is used for device configuration and which is not associated with any interface.

When a USB device is first connected to a USB host, the USB device enumeration process is started. The enumeration starts by sending a reset signal to the USB device. The speed of the USB device is determined during the reset signaling. After reset, the USB device's information is read by the host, then the device is assigned a unique 7-bit address. If the device is supported by the host, the device drivers needed for communicating with the device are loaded and the device is set to a configured state. If the USB host is restarted, the enumeration process is repeated for all connected devices.

The host controller polls the bus for traffic, usually in a round-robin fashion, so no USB device can transfer any data on the bus without an explicit request from the host controller.

The computer hardware that contains the host controller and the root hub has an interface geared toward the programmer which is called Host Controller Device (HCD) and is defined by the hardware implementer..... Continue

Data and source mostly taken from Wikipedia

USB Flash Drive

Today developing of technology is move to mobile. We can see it from telephone , being handphone , PC (Personal Computer) being Laptop and even Pocket PC , etc. Automatically need of mobile storage is being important. For the solution there is USB flash drive. We can say this is the best invention for mobile storage media so far.

For knowing more about USB flash drive , let’s look bellow.

A USB flash drive consists of a NAND-type flash memory data storage device integrated with a USB (universal serial bus) interface. USB flash drives are typically removable and rewritable, much shorter than a floppy disk (1 to 4 inches or 2.5 to 10 cm), and weigh less than 2 ounces (56 g). Storage capacities typically range from 64 MB to 64 GB with steady improvements in size and price per gigabyte. Some allow 1 million write or erase cycles and have 10-year data retention, connected by USB 1.1 or USB 2.0.

USB flash drives offer potential advantages over other portable storage devices, particularly the floppy disk. They have a more compact shape, operate faster, hold much more data, have a more durable design, and operate more reliably due to their lack of moving parts. Additionally, it has become increasingly common for computers to ship without floppy disk drives. USB ports, on the other hand, appear on almost every current mainstream PC and laptop. These types of drives use the USB mass storage standard, supported natively by modern operating systems such as Windows, Mac OS X, Linux, and other Unix-like systems. USB drives with USB 2.0 support can also operate faster than an optical disc drive, while storing a larger amount of data in a much smaller space.

Nothing actually moves 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.

A flash drive consists of a small printed circuit board protected inside a plastic, metal, or rubberised case, robust enough for carrying with no additional protection — in a pocket or on a key chain, for example. The USB connector is protected by a removable cap or by retracting into the body of the drive, although it is not liable to be damaged if exposed. Most flash drives use a standard type-A USB connection allowing plugging into a port on a personal computer.

Flash memory combines a number of older technologies, with the low cost, low power consumption and small size made possible by recent advances in microprocessor technology. The memory storage is based on earlier EPROM and EEPROM technologies. These had very limited capacity, were very slow for both reading and writing, required complex high-voltage drive circuitry, and could only be re-written after erasing the entire contents of the chip.

Hardware designers later developed EEPROMS with the erasure region broken up into smaller "fields" that could be erased individually without affecting the others. Altering the contents of a particular memory location involved first copying the entire field into an off-chip buffer memory, erasing the field, and then re-writing the data back into the same field, making the necessary alteration to the relevant memory location while doing so. This required considerable computer support, and PC-Based EEPROM flash memory systems often carried their own dedicated microprocessor system. Flash drives are more or less a miniaturized version of this.

The development of high-speed serial data interfaces such as USB for the first time made memory systems with serially accessed storage viable, and the simultaneous development of small, high-speed, low-power microprocessor systems allowed this to be incorporated into extremely compact systems. Serial access also greatly reduced the number of electrical connections required for the memory chips, which has allowed the successful manufacture of multi-gigabyte capacities. (Every external electrical connection is a potential source of manufacturing failure, and with traditional manufacturing, a point is rapidly reached where the successful yield approaches zero).

Computers access modern flash memory systems very much like hard disk drives, where the controller system has full control over where information is actually stored. The actual EEPROM writing and erasure processes are, however, still very similar to the earlier systems described above.

Many low-cost MP3 Players simply add extra software to a standard flash memory control microprocessor so it can also serve as a music playback decoder. Most of these players can also be used as a conventional flash drive.

First commercial product

Trek Technology and IBM began selling the first USB flash drives commercially in 2000. Singaporean company Trek Technology sold a model dubbed the "ThumbDrive," and IBM marketed the first such drives in North America, with its product the "DiskOnKey" (which was manufactured by M-Systems). IBM's USB flash drive became available December 15, 2000, and had a storage capacity of 8 MB, more than five times the capacity of the (at the time) commonly used floppy disks.

In 2000 Lexar introduced a Compact Flash (CF) card with a USB connection, and a companion card read/writer and USB cable that eliminated the need for a USB hub.

In 2004 Trek Technology brought several lawsuits against other USB flash drive manufacturers and distributors in an attempt to assert its patent rights to the USB flash drive. A court in Singapore ordered competitors to cease selling similar products that would be covered by Trek's patent, but a court in the United Kingdom revoked one of Trek's patents in that country.

Second generation

Modern flash drives have USB 2.0 connectivity. However, they do not currently use the full 480 MBit/s (60MB/s) the USB 2.0 Hi-Speed specification supports due to technical limitations inherent in NAND flash. The fastest drives currently available use a dual channel controller, although they still fall considerably short of the transfer rate possible from a current generation hard disk, or the maximum high speed USB throughput.

Typical overall file transfer speeds vary considerably, and should be checked before purchase; speeds may be given in megabytes or megabits per second. Typical fast drives claim to read at up to 30 megabytes/s (MB/s) and write at about half that. Older "USB full speed" 12 megabit/s devices are limited to a maximum of about 1 MB/s.

One end of the device is fitted with a single male type-A USB connector. Inside the plastic casing is a small printed circuit board. Mounted on this board is some simple power circuitry and a small number of surface-mounted integrated circuits (ICs). Typically, one of these ICs provides an interface to the USB port, another drives the onboard memory, and the other is the flash memory.

Drives typically use the USB mass storage device class to communicate with the host.

Essential components

There are typically four parts to a flash drive:

• Male type-A USB connector — provides an interface to the host computer.
• USB mass storage controller — implements the USB host controller. The controller contains a small microcontroller with a small amount of on-chip ROM and RAM.
• NAND flash memory chip — stores data. NAND flash is typically also used in digital cameras.
• Crystal oscillator — produces the device's main 12 MHz clock signal and controls the device's data output through a phase-locked loop.

Additional components

The typical device may also include:

• Jumpers and test pins — for testing during the flash drive's manufacturing or loading code into the microprocessor.
• LEDs — indicate data transfers or data reads and writes.
• Write-protect switches — indicate whether the device should be in "write-protection" mode.
• Unpopulated space — provides space to include a second memory chip. Having this second space allows the manufacturer to develop only one printed circuit board that can be used for more than one storage size device, to meet the needs of the market.
• USB connector cover or cap — reduces the risk of damage and prevents the ingress of fluff or other contaminants, and improves overall device appearance. Some flash drives do not feature a cap, but instead have retractable USB connectors. Other flash drives have a "swivel" cap that is permanently connected to the drive itself and eliminates the chance of losing the cap.
• Transport aid — the cap or the main body often contains a hole suitable for connection to a key chain or lanyard.
• Some drives offer expandable storage via an internal memory card slot, much like a memory card reader.

.... Continue

Data and source mostly taken from Wikipedia

Sound Card

Nowadays , people not just use computer for doing their work but also as entertainer for them. They usually use computer for watching movie and hearing a music. To make an voice output computer need a tools that called Sound Card.

To know more about sound card . let’s see a little explanation bellow.

A sound card (also known as an audio card) is a computer expansion card that facilitates the input and output of audio signals to/from a computer under control of computer programs. Typical uses of sound cards include providing the audio component for multimedia applications such as music composition, editing video or audio, presentation/education, and entertainment (games). Many computers have sound capabilities built in, while others require additional expansion cards to provide for audio capability.

Sound cards usually feature a digital-to-analog converter, that converts recorded or generated digital data into an analog format. The output signal is connected to an amplifier, headphones, or external device using standard interconnects, such as a TRS connector or an RCA connector. If the number and size of connectors is too large for the space on the backplate the connectors will be off-board, typically using a breakout box, or an auxiliary backplate. More advanced cards usually include more than one sound chip to provide for higher data rates and multiple simultaneous functionality, eg between digital sound production and synthesized sounds (usually for real-time generation of music and sound effects using minimal data and CPU time). Digital sound reproduction is usually done with multi-channel DACs, which are capable of multiple digital samples simultaneously at different pitches and volumes, or optionally applying real-time effects like filtering or distortion. Multi-channel digital sound playback can also be used for music synthesis when used with a digitized instrument bank, typically a small amount of ROM or Flash memory containing samples corresponding to MIDI instruments. A contrasting way to synthesize sound on a PC uses "audio codecs", which rely heavily on software for music synthesis, MIDI compliance, and even multiple-channel emulation. This approach has become common as manufacturers seek to simplify the design and the cost of sound cards.

Most sound cards have a line in connector for signal from a cassette tape recorder or similar sound source. The sound card digitizes this signal and stores it (under control of appropriate matching computer software) on the computer's hard disk for storage, editing, or further processing. Another common external connector is the microphone connector, for use by a microphone or other low level input device. Input through a microphone jack can then be used by speech recognition software or for Voice over IP applications.

Another important characteristic of sound cards is polyphony, which is more than one distinct voice or sound playable simultaneously and independently, and the number of simultaneous channels. These are intended as the number of distinct electrical audio outputs, which may correspond to a speaker configuration such as 2.0 (stereo), 2.1 (stereo and sub woofer), 5.1 etc. Sometimes, the terms "voices" and "channels" are used interchangeably to indicate the degree of polyphony, not the output speaker configuration.

For example, many older sound chips could accommodate three voices, but only one audio channel (ie, a single mono output) for output, requiring all voices to be mixed together. More recent cards, such as the AdLib sound card, have a 9 voice polyphony and 1 mono channel as a combined output.

For some years, most PC sound cards have had multiple FM synthesis voices (typically 9 or 16) which were usually used for MIDI music. The full capabilities of advanced cards aren't often completely used; only one (mono) or two (stereo) voice(s) and channel(s) are usually dedicated to playback of digital sound samples, and playing back more than one digital sound sample usually requires a software downmix at a fixed sampling rate. Modern low-cost integrated soundcards (ie, those built into motherboards) such as audio codecs like those meeting the AC'97 standard and even some budget expansion soundcards still work that way. They may provide more than two sound output channels (typically 5.1 or 7.1 surround sound), but they usually have no actual hardware polyphony for either sound effects or MIDI reproduction, these tasks are performed entirely in software. This is similar to the way inexpensive softmodems perform modem tasks in software rather than in hardware).

Also, in the early days of wavetable synthesis, some sound card manufacturers advertised polyphony solely on the MIDI capabilities alone. In this case, the card's output channel is irrelevant (and typically, the card is only capable of two channels of digital sound). Instead, the polyphony measurement solely applies to the amount of MIDI cool the sound card is capable of producing at one given time.

Today, a sound card providing actual hardware polyphony, regardless of the number of output channels, is typically referred to as a "hardware audio accelerator", although actual voice polyphony is not the sole (or even a necessary) prerequisite, with other aspects such as hardware acceleration of 3D sound, positional audio and real-time DSP effects being more important....... Continue

Data and source mostly taken from Wikipedia

Keyboard (computing)

In computer system there is an input and output tools, for this time I will explain about an input tools Keyboard and Mouse. Because , we can say these two things as a crucial input component for computer system. Computer System without Keyboard and Mouse is Nonsense.

For more let’s see bellow.

Keyboard (computing)

In computing, a keyboard is an input device partially modelled after the typewriter keyboard which uses an arrangement of buttons, or keys which act as electronic switches. A keyboard typically has characters engraved or printed on the keys, and each press of a key typically corresponds to a single written symbol. However, to produce some symbols requires pressing and holding several keys simultaneously or in sequence. While most keyboard keys produce letters, numbers or signs (characters), other keys or simultaneous key presses can produce actions or computer commands.

In normal usage, the keyboard is used to type text or numbers into a word processor, text editor, or other program. In a modern computer the interpretation of keypresses is generally left to the software. A computer keyboard distinguishes each physical key from every other and reports all keypresses to the controlling software. Keyboards are also used for computer gaming, either with regular keyboards or by using special gaming keyboards which can expedite frequently used keystroke combinations. A keyboard is also used give commands to the operating system of a computer, such as the Control-Alt-Delete combination, which brings up a task window or shuts down the machine.

Standard keyboards such as the 104-key Windows keyboards include alphabetic characters, punctuation symbols, numbers, and a variety of function keys. The internationally-common 102/105 key keyboards have a smaller 'left shift' key and an additional key with some more symbols between that and the letter to its right (usually Z or Y).

Keyboards with extra keys such as multimedia keyboards have special keys for accessing music, web, and other oft-used programs, a mute button, volume buttons or knob, and standby (sleep) button. Gaming keyboards have extra function keys which can be programmed with keystroke macros. For example, ctrl+shift+y could be a keystroke that is frequently used in a certain computer game. Shortcuts marked on color-coded keys are used for some software applications and for specialized for uses including word processing, video editing, graphic design, and audio editing.

Smaller keyboards have been introduced for laptops, PDAs, cellphones, or users who have a limited workspace. The size of a standard keyboard is dictated by the practical consideration that the keys must be large enough to be easily pressed by fingers. To reduce the size of the keyboard, the numeric keyboard to the right of the alphabetic keyboard can be removed, or the size of the keys can be reduced, which makes it harder to enter text. Another way to reduce the size of the keyboard is to reduce the number of keys and use chording keyer, i.e. pressing several keys simultaneously. For example, the GKOS keyboard has been designed for small wireless devices. Other two-handed alternatives more akin to a game controller, such as the alphagrip, are also used as a way to input data and text. Another way to reduce the size of a keyboard is to use smaller buttons and pack them closer together. Such keyboards, often called a "thumbboard" (thumbing) are used in some personal digital assistants such as the Treo and BlackBerry and some Ultra-Mobile PCs such as the OQO.

Numeric keyboards contain only numbers, mathematical symbols for addition, subtraction, multiplication, and division, a decimal point, and several function keys (e.g. End, Delete, etc.). They are often used to facilitate data entry with smaller keyboard-equipped laptops or with smaller keyboards that do not have a numeric keypad.

Non-standard or special-use types

A keyset or chorded keyboard (also called a chord keyboard or chording keyboard) is a computer input device that allows the user to enter characters or commands formed by pressing several keys together, like playing a "chord" on a piano. The large number of combinations available from a small number of keys allows text or commands to be entered with one hand, leaving the other hand free to do something else. A secondary advantage is that it can be built into a device (such as a pocket-sized computer) that is too small to contain a normal sized keyboard. A chorded keyboard designed to be used while held in the hand is called a keyer.

Virtual keyboards, such as the I-Tech Virtual Laser Keyboard, project an image of a full-size keyboard onto a surface. Sensors in the projection unit identify which key is being "pressed" and relay the signals to a computer or personal digital assistant. There is also a virtual keyboard, the On-Screen Keyboard, for use on WIndows.

Touchscreens such as with the iPhone and the OLPC laptop can be used as a keyboard. (The OLPC initiative's second computer will be effectively two tablet touchscreens hinged together like a book. It can be used as a convertible tablet PC where the keyboard is one half-screen (one side of the book) which turns into a touchscreen virtual keyboard.)

Foldable keyboards are made of soft plastic which can be rolled or folded over for travel. When in use, the keyboard can conform to uneven surfaces, and it is more resistant to liquids than a standard keyboard.

Alphabetic layout

There are a number of different arrangements of alphabetic, numeric, and punctuation symbols on keys. These different keyboard layouts arise mainly because different people need easy access to different symbols, either because they are inputting text in different languages, or because they need a specialized layout for mathematics, accounting, computer programming, or other purposes. Most of the more common keyboard layouts (QWERTY-based and similar) were designed in the era of the mechanical typewriters, so their ergonomics had to be slightly compromised in order to tackle some of the mechanical limitations of the typewriter. As the letter-keys were attached to levers that needed to move freely, inventor Christopher Sholes developed the QWERTY layout to reduce the likelihood of jamming. With the advent of computers, lever jams are no longer an issue, but nevertheless, QWERTY layouts were adopted for electronic keyboards because they were widely used. Alternative layouts such as the Dvorak Simplified Keyboard are not in widespread use.

The QWERTZ layout is fairly widely used in Germany and much of Central Europe. The main difference between it and QWERTY is that Y and Z are swapped, and most special characters such as brackets are replaced by diacritical characters. Another situation takes place with “national” layouts. Keyboards designed for typing in Spanish have some characters shifted, to release the space for Ñ ñ; similarly, those for French and other European languages may have a special key for the character Ç ç . The AZERTY layout is used in France, Belgium and some neighbouring countries. It differs from the QWERTY layout in that the A and Q are swapped, the Z and W are swapped, and the M is moved from the right of N to the right of L (where colon/semicolon is on a US keyboard). The digits 0 to 9 are on the same keys, but to be typed the shift key must be pressed. The unshifted positions are used for accented characters.

Keyboards designed for non-English speaking markets may have special keys to switch between non-English typing and the Roman alphabet and vice-versa. In Japan, keyboards often can be switched between Japanese and the Roman alphabet, and the character ¥ (the Yen currency) is used instead of "\". In Israel, keyboards can often be switched between Hebrew and English. In bilingual regions of Canada and in the French-speaking province of Quebec, keyboards can often be switched between an English and a French-language keyboard; while both keyboards share the same QWERTY alphabetic layout, the French-language keyboard enables the user to type accented vowels such as "é" or "à" with a single keystroke. Using keyboards for other languages leads to a conflict: the image on the key does not correspond to the character. In such cases, each new language may require an additional label on the keys, because the standard keyboard layouts do not share even similar characters of different languages (see the example in the figure above)......... Continue

Data and source mostly taken from Wikipedia

Bluetooth

Today we usually use Bluetooth in our activity actually that contain about telecommunication such as our phone. We usually share our data (in our phone or computer) with our friend using Bluetooth. I think these is one thing tha t we have to know about. Such as what is Bluetooth exactly . that is a thing? , why is Bluetooth so special and one of powerful thing in telecommunication word.

For further I will try to explain a little about Bluetooth below here.

Bluetooth is a wireless protocol utilizing short-range communications technology facilitating data transmission over short distances from fixed and mobile devices, creating wireless personal area networks (PANs). The intent behind the development of Bluetooth was the creation of a single digital wireless protocol, capable of connecting multiple devices and overcoming problems arising from synchronization of these devices. Bluetooth uses a radio technology called frequency hopping spread spectrum. It chops up the data being sent and transmits chunks of it on up to 79 different frequencies. In its basic mode, the modulation is Gaussian frequency shift keying (GFSK). It can achieve a gross data rate of 1 Mb/s. Bluetooth provides a way to connect and exchange information between devices such as mobile phones, telephones, laptops, personal computers, printers, GPS receivers, digital cameras, and video game consoles through a secure, globally unlicensed Industrial, Scientific, and Medical (ISM) 2.4 GHz short-range radio frequency bandwidth. The Bluetooth specifications are developed and licensed by the Bluetooth Special Interest Group (SIG). The Bluetooth SIG consists of companies in the areas of telecommunication, computing, networking, and consumer electronics.

Bluetooth is a standard and communications protocol primarily designed for low power consumption, with a short range (power-class-dependent: 1 meter, 10 meters, 100 meters) based on low-cost transceiver microchips in each device. Bluetooth makes it possible for these devices to communicate with each other when they are in range. Because the devices use a radio communications system, they do not have to be in line of sight of each other; they can even be far apart if the transmission has sufficient power.

In order to use Bluetooth, a device must be compatible with certain Bluetooth profiles. These define the possible applications and uses of the technology

List of applications

More prevalent applications of Bluetooth include:

• Wireless control of and communication between a mobile phone and a hands-free headset. This was one of the earliest applications to become popular.
• Wireless networking between PCs in a confined space and where little bandwidth is required.
• Wireless communication with PC input and output devices, the most common being the mouse, keyboard and printer.
• Transfer of files between devices with OBEX.
• Transfer of contact details, calendar appointments, and reminders between devices with OBEX.
• Replacement of traditional wired serial communications in test equipment, GPS receivers, medical equipment, bar code scanners, and traffic control devices.
• For controls where infrared was traditionally used.
• Sending small advertisements from Bluetooth-enabled advertising hoardings to other, discoverable, Bluetooth devices.
• Two seventh-generation game consoles, Nintendo's Wii and Sony's PlayStation 3, use Bluetooth for their respective wireless controllers.
• Dial-up internet access on personal computers or PDAs using a data-capable mobile phone as a modem.

A personal computer must have a Bluetooth adapter in order to communicate with other Bluetooth devices (such as mobile phones, mice and keyboards). While some desktop computers and most recent laptops come with a built-in Bluetooth adapter, others will require an external one in the form of a dongle.

Unlike its predecessor, IrDA, which requires a separate adapter for each device, Bluetooth allows multiple devices to communicate with a computer over a single adapter.

Operating system support

Apple has supported Bluetooth since Mac OS X v10.2 which was released in 2002.

For Microsoft platforms, Windows XP Service Pack 2 and later releases have native support for Bluetooth. Previous versions required users to install their Bluetooth adapter's own drivers, which were not directly supported by Microsoft. Microsoft's own Bluetooth dongles (packaged with their Bluetooth computer devices) have no external drivers and thus require at least Windows XP Service Pack 2.

Linux has two popular Bluetooth stacks, BlueZ and Affix. The BlueZ stack is included with most Linux kernels and it was originally developed by Qualcomm. The Affix stack was developed by Nokia. FreeBSD features Bluetooth support since its 5.0 release.NetBSD features Bluetooth support since its 4.0 release. Its Bluetooth stack has been ported to OpenBSD as well.

A mobile phone that is Bluetooth enabled is able to pair with many devices. To ensure the broadest support of feature functionality together with legacy device support, the OMTP forum has recently published a recommendations paper, entitled "Bluetooth Local Connectivity"; see external links below to download this paper.

This publication recommends two classes, Basic and Advanced, with requirements that cover imaging, printing, stereo audio and in-car usage

Specifications and features

The Bluetooth specification was developed in 1994 by Jaap Haartsen and Sven Mattisson, who were working for Ericsson Mobile Platforms in Lund, Sweden.The specification is based on frequency-hopping spread spectrum technology.

The specifications were formalized by the Bluetooth Special Interest Group (SIG). The SIG was formally announced on May 20, 1998. Today it has a membership of over 11,000 companies worldwide. It was established by Ericsson, IBM, Intel, Toshiba, and Nokia, and later joined by many other companies.

Bluetooth 1.0 and 1.0B

Versions 1.0 and 1.0B had many problems, and manufacturers had difficulty making their products interoperable. Versions 1.0 and 1.0B also included mandatory Bluetooth hardware device address (BD_ADDR) transmission in the Connecting process (rendering anonymity impossible at the protocol level), which was a major setback for certain services planned for use in Bluetooth environments.

Bluetooth 1.1

• Ratified as IEEE Standard 802.15.1-2002.
• Many errors found in the 1.0B specifications were fixed.
• Added support for non-encrypted channels.
• Received Signal Strength Indicator (RSSI).

Bluetooth 1.2

This version is backward-compatible with 1.1 and the major enhancements include the following:

• Faster Connection and Discovery
• Adaptive frequency-hopping spread spectrum (AFH), which improves resistance to radio frequency interference by avoiding the use of crowded frequencies in the hopping sequence.
• Higher transmission speeds in practice, up to 721 kbit/s, than in 1.1.
• Extended Synchronous Connections (eSCO), which improve voice quality of audio links by allowing retransmissions of corrupted packets, and may optionally increase audio latency to provide better support for concurrent data transfer.
• Host Controller Interface (HCI) support for three-wire UART.
• Ratified as IEEE Standard 802.15.1-2005.

Bluetooth 2.0

This version of the Bluetooth specification was released on November 10, 2004. It is backward-compatible with the previous version 1.1. The main difference is the introduction of an Enhanced Data Rate (EDR) for faster data transfer. The nominal rate of EDR is about 3 megabits per second, although the practical data transfer rate is 2.1 megabits per second. The additional throughput is obtained by using a different radio technology for transmission of the data. Standard, or Basic Rate, transmission uses Gaussian Frequency Shift Keying (GFSK) modulation of the radio signal; EDR uses a combination of GFSK and Phase Shift Keying (PSK) modulation.

According to the 2.0 specification, EDR provides the following benefits:

• Three times faster transmission speed — up to 10 times (2.1 MBit/s) in some cases.
• Reduced complexity of multiple simultaneous connections due to additional bandwidth.
• Lower power consumption through a reduced duty cycle.

The Bluetooth Special Interest Group (SIG) published the specification as "Bluetooth 2.0 + EDR" which implies that EDR is an optional feature. Aside from EDR, there are other minor improvements to the 2.0 specification, and products may claim compliance to "Bluetooth 2.0" without supporting the higher data rate. At least one commercial device, the HTC TyTN pocket PC phone, states "Bluetooth 2.0 without EDR" on its data sheet.

Bluetooth 2.1

Bluetooth Core Specification Version 2.1 is fully backward-compatible with 1.1, and was adopted by the Bluetooth SIG on July 26, 2007.This specification includes the following features:

• Extended inquiry response: provides more information during the inquiry procedure to allow better filtering of devices before connection. This information includes the name of the device, a list of services the device supports, plus other information like the time of day and pairing information.

• Sniff subrating: reduces the power consumption when devices are in the sniff low-power mode, especially on links with asymmetric data flows. Human interface devices (HID) are expected to benefit the most, with mouse and keyboard devices increasing their battery life by a factor of 3 to 10. It lets devices decide how long they will wait before sending keepalive messages to one another. Previous Bluetooth implementations featured keep alive message frequencies of up to several times per second. In contrast, the 2.1 specification allows pairs of devices to negotiate this value between them to as infrequently as once every 5 or 10 seconds.

• Encryption Pause Resume: enables an encryption key to be refreshed, enabling much stronger encryption for connections that stay up for longer than 23.3 hours (one Bluetooth day).

• Secure Simple Pairing: radically improves the pairing experience for Bluetooth devices, while increasing the use and strength of security. It is expected that this feature will significantly increase the use of Bluetooth.

• Near Field Communication (NFC) cooperation: automatic creation of secure Bluetooth connections when NFC radio interface is also available. This functionality is part of the Secure Simple Pairing where NFC is one way of exchanging pairing information. For example, a headset should be paired with a Bluetooth 2.1 phone including NFC just by bringing the two devices close to each other (a few centimeters). Another example is automatic uploading of photos from a mobile phone or camera to a digital picture frame just by bringing the phone or camera close to the frame.

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Data and source mostly taken from Wikipedia.

BIOS

Today , every computer has BIOS as connector from hardware to software. We can say the function of BIOS here is very important too such like CPU , Motherboard , Ram , Harddisk Drive in computer system.

Because of that , i think we have to know what is BIOS exactly mean, and for that i have a little explanation about BIOS bellow here .

In computing, the BIOS is an acronym that stands either for the Basic Input/Output System or for Built In Operating System (see Acronym definition). The latter term dates from the late 1970s and early 1980s when the PCs of the day normally contained a comprehensive operating system in their ROMs. The latter acronym is still much used in conjunction with gadgetry containing dedicated computers, such as modern cameras, white-wear, etc. The underlying technology is very similar, being little more than a matter of size.

BIOS refers, in part, to the firmware code (a type of boot loader) run by a PC when first powered on. The primary function of the BIOS is to identify and initialize system component hardware (such as the video display card, hard disk, and floppy disk) and some other hardware devices. This is to prepare the machine into a known low capability state, so other software programs stored on various media can be loaded, executed, and given control of the PC.This process is known as booting, or booting up, which is short for bootstrapping.

The BIOSes of IBM PC class machines are coded programs embedded on a chip that recognize and control various devices that make up x86 personal computers, and provide a small library of basic Input/Output functions that can be called to operate and control the peripherals such as the keyboard, primitive (800 x 600) display functions and so forth.

Computers designed to run Windows ME or Windows 2000, or later, supersede this basic monitor functionality by taking over direct control of the interrupt table and replacing the monitor routines with faster and more robust low-level modules that, unlike the BIOS function set, are re-entrant. Various BIOS functions in ROM were left in control in earlier Windows versions, and the BIOS only comes into play today in the alternate shell Cmd.exe, or if the machine is booted into a legacy DOS version

The term first appeared in the CP/M operating system, describing the part of CP/M loaded during boot time that interfaced directly with the hardware (CP/M machines usually had a simple boot loader in ROM, and nothing else). Most versions of DOS have a file called "IBMBIO.COM" or "IO.SYS" that is analogous to the CP/M disk BIOS. The term was also known as Binary Input/Output System and Basic Integrated Operating System.

Among other classes of computers, the generic terms boot monitor, boot loader or boot ROM were commonly used. Some Sun and Macintosh PowerPC computers used Open Firmware for this purpose. There are a few alternatives for Legacy BIOS in the x86 world: Extensible Firmware Interface, Open Firmware (used on the OLPC XO-1) and corebot.

Prior to the early 1990s, BIOSes were stored in ROM or PROM chips, which could not be altered by users. As its complexity and need for updates grew, and re-programmable parts became more available, BIOS firmware was most commonly stored on EEPROM or flash memory devices. According to Robert Braver, the president of the BIOS manufacturer Micro Firmware, Flash BIOS chips became common around 1995 because the electrically erasable PROM (EEPROM) chips are cheaper and easier to program than standard erasable PROM (EPROM) chips. PROM chips may be erased by prolonged exposure to ultraviolet light, which accessed the chip via the window. Chip manufacturers use PROM blasters to reprogram EPROM chips. EEPROM chips come with the additional feature of allowing a BIOS reprogramming via higher-than-normal amounts of voltage.BIOS versions are upgraded to take advantage of newer versions of hardware and to correct bugs in previous revisions of BIOSes.

The first flash chips attached to the ISA bus. Starting in 1997, the BIOS flash moved to the LPC bus, a functional replacement for ISA, following a new standard implementation known as "firmware hub" (FWH). Most BIOS revisions created in 1995 and nearly all BIOS revisions in 1997 supported the year 2000. In 2006, the first systems supporting a Serial Peripheral Interface (SPI) appeared, and the BIOS flash moved again......... Continue

Data and source mostly taken from Wikipedia.

Computer Operating System

Microsoft Windows

Microsoft Windows is a series of software operating systems and graphical user interfaces produced by Microsoft. Microsoft first introduced an operating environment named Windows in November 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces (GUIs). Microsoft Windows came to dominate the world's personal computer market, overtaking Mac OS, which had been introduced previously. At the 2004 IDC Directions conference, it was stated that Windows had approximately 90% of the client operating system market. The most recent client version of Windows is Windows Vista; the most recent server version is Windows Server 2008.

Versions

16-bit operating environments

The early versions of Windows were often thought of as just graphical user interfaces, mostly because they ran on top of MS-DOS and used it for file system services.However, even the earliest 16-bit Windows versions already assumed many typical operating system functions, notably, having their own executable file format and providing their own device drivers (timer, graphics, printer, mouse, keyboard and sound) for applications. Unlike MS-DOS, Windows allowed users to execute multiple graphical applications at the same time, through cooperative multitasking. Finally, Windows implemented an elaborate, segment-based, software virtual memory scheme, which allowed it to run applications larger than available memory: code segments and resources were swapped in and thrown away when memory became scarce, and data segments moved in memory when a given application had relinquished processor control, typically waiting for user input. 16-bit Windows versions include Windows 1.0 (1985), Windows 2.0 (1987) and its close relatives, Windows/286-Windows/386.

Hybrid 16/32-bit operating environments

Windows/386 introduced a 32-bit protected mode kernel and virtual machine monitor. For the duration of a Windows session, it created one or more virtual 8086 environments and provided device virtualization for the video card, keyboard, mouse, timer and interrupt controller inside each of them. The user-visible consequence was that it became possible to preemptively multitask multiple MS-DOS environments in separate windows, although graphical MS-DOS applications required full screen mode. Also, Windows applications were multi-tasked cooperatively inside one such virtual 8086 environment.

Windows 3.0 (1990) and Windows 3.1 (1992) improved the design, mostly because of virtual memory and loadable virtual device drivers (VxDS) which allowed them to share arbitrary devices between multitasked DOS windows. Also, Windows applications could now run in protected mode (when Windows was running in Standard or 386 Enhanced Mode), which gave them access to several megabytes of memory and removed the obligation to participate in the software virtual memory scheme. They still ran inside the same address space, where the segmented memory provided a degree of protection, and multi-tasked cooperatively. For Windows 3.0, Microsoft also rewrote critical operations from C into assembly, making this release faster and less memory-hungry than its predecessors.

Hybrid 16/32-bit operating systems

With the introduction of the 32-bit Windows for Workgroups 3.11, Windows was able to stop relying on DOS for file management. Leveraging this, Windows 95 introduced Long File Names, reducing the 8.3 filename DOS environment to the role of a boot loader. MS-DOS was now bundled with Windows; this notably made it (partially) aware of long file names when its utilities were run from within Windows. The most important novelty was the possibility of running 32-bit multi-threaded preemptively multitasked graphical programs. However, the necessity of keeping compatibility with 16-bit programs meant the GUI components were still 16-bit only and not fully reentrant, which resulted in reduced performance and stability.

There were three releases of Windows 95 (the first in 1995, then subsequent bug-fix versions in 1996 and 1997, only released to OEMs, which added extra features such as FAT32 and primitive USB support). Microsoft's next OS was Windows 98; there were two versions of this (the first in 1998 and the second, named "Windows 98 Second Edition", in 1999). In 2000, Microsoft released Windows Me (Me standing for Millennium Edition), which used the same core as Windows 98 but adopted some aspects of Windows 2000 and removed the option boot into DOS mode. It also added a new feature called System Restore, allowing the user to set the computer's settings back to an earlier date.

32-bit operating systems

The NT family of Windows systems was fashioned and marketed for higher reliability business use, and was unencumbered by any Microsoft DOS patrimony. The first release was MS Windows NT 3.1 (1993, numbered "3.1" to match the consumer Windows version, which was followed by NT 3.5 (1994), NT 3.51 (1995), NT 4.0 (1996), and Windows 2000 (2000). NT 4.0 was the first in this line to implement the "Windows 95" user interface (and the first to include Windows 95’s built-in 32-bit runtimes). Microsoft then moved to combine their consumer and business operating systems with Windows XP, coming in both home and professional versions (and later niche market versions for tablet PCs and media centers); they also diverged release schedules for server operating systems. Windows Server 2003, released a year and a half after Windows XP, brought Windows Server up to date with MS Windows XP. After a lengthy development process, Windows Vista was released toward the end of 2006, and its server counterpart, Windows Server 2008 was released in early 2008.

Windows CE, Microsoft’s offering in the mobile and embedded markets, is also a true 32-bit operating system that offers various services for all sub-operating workstations.

64-bit operating systems

Windows NT included support for several different platforms before the x86-based personal computer became dominant in the professional world. Versions of NT from 3.1 to 4.0 variously supported PowerPC, DEC Alpha and MIPS R4000, some of which were 64-bit processors, although the operating system treated them as 32-bit processors.

With the introduction of the Intel Itanium architecture, which is referred to as IA-64, Microsoft released new versions of Windows to support it. Itanium versions of Windows XP and Windows Server 2003 were released at the same time as their mainstream x86 (32-bit) counterparts. On April 25, 2005, Microsoft released Windows XP Professional x64 Edition and x64 versions of Windows Server 2003 to support the AMD64/Intel64 (or x64 in Microsoft terminology) architecture. Microsoft dropped support for the Itanium version of Windows XP in 2005. Windows Vista is the first end-user version of Windows that Microsoft has released simultaneously in 32-bit and x64 editions. Windows Vista does not support the Itanium architecture. The modern 64-bit Windows family comprises AMD64/Intel64 versions of Windows Vista, and Windows Server 2003 and Windows Server 2008, in both Itanium and x64 editions.

Microsoft has taken two parallel routes in its operating systems. One route has been for the home user and the other has been for the professional IT user. The dual routes have generally led to home versions having greater multimedia support and less functionality in networking and security, and professional versions having inferior multimedia support and better networking and security.

The first version of Microsoft Windows, version 1.0, released in November 1985, lacked a degree of functionality and achieved little popularity, and was to compete with Apple’s own operating system. Windows 1.0 is not a complete operating system; rather, it extends MS-DOS. Microsoft Windows version 2.0 was released in November, 1987 and was slightly more popular than its predecessor. Windows 2.03 (release date January 1988) had changed the OS from tiled windows to overlapping windows. The result of this change led to Apple Computer filing a suit against Microsoft alleging infringement on Apple's copyrights

Microsoft Windows version 3.0, released in 1990, was the first Microsoft Windows version to achieve broad commercial success, selling 2 million copies in the first six months.It featured improvements to the user interface and to multitasking capabilities. It received a facelift in Windows 3.1, made generally available on March 1, 1992. Windows 3.1 support ended on December 31, 2001.

In July 1993, Microsoft released Windows NT based on a new kernel. NT was considered to be the professional OS and was the first Windows version to utilize preemptive multitasking.. Windows NT would later be retooled to also function as a home operating system, with Windows XP.

On August 24, 1995, Microsoft released Windows 95, a new, and major, consumer version that made further changes to the user interface, and also used preemptive multitasking. Windows 95 was designed to replace not only Windows 3.1, but also Windows for Workgroups, and MS-DOS. It was also the first Windows operating system to use Plug and Play capabilities. The changes Windows 95 brought to the desktop were revolutionary, as opposed to evolutionary, such as those in Windows 98 and Windows Me. Mainstream support for Windows 95 ended on December 31, 2000 and extended support for Windows 95 ended on December 31, 2001.

The next in the consumer line was Microsoft Windows 98 released on June 25, 1998. It was substantially criticized for its slowness and for its unreliability compared with Windows 95, but many of its basic problems were later rectified with the release of Windows 98 Second Edition in 1999.Mainstream support for Windows 98 ended on June 30, 2002 and extended support for Windows 98 ended on July 11, 2006. As part of its "professional" line, Microsoft released Windows 2000 in February 2000. The consumer version following Windows 98 was Windows Me (Windows Millennium Edition). Released in September 2000, Windows Me implemented a number of new technologies for Microsoft: most notably publicized was "Universal Plug and Play."

In October 2001, Microsoft released Windows XP, a version built on the Windows NT kernel that also retained the consumer-oriented usability of Windows 95 and its successors. This new version was widely praised in computer magazines. It shipped in two distinct editions, "Home" and "Professional", the former lacking many of the superior security and networking features of the Professional edition. Additionally, the first "Media Center" edition was released in 2002, with an emphasis on support for DVD and TV functionality including program recording and a remote control. Mainstream support for Windows XP will continue until April 14, 2009 and extended support will continue until April 8, 2014.

In April 2003, Windows Server 2003 was introduced, replacing the Windows 2000 line of server products with a number of new features and a strong focus on security; this was followed in December 2005 by Windows Server 2003 R2.

On January 30, 2007 Microsoft released Windows Vista. It contains a number of new features, from a redesigned shell and user interface to significant technical changes, with a particular focus on security features. It is available in a number of different editions, and has been subject to some criticism........Continue

Data and source mostly taken from Wikipedia.

Peripheral Component Interconnect (PCI)

The Peripheral Component Interconnect, or PCI Local Bus (commonly PCI), specifies a computer bus for attaching peripheral devices to a computer motherboard. These devices can take any one of the following forms:

• An integrated circuit fitted onto the motherboard itself, called a planar device in the PCI specification.
• An expansion card that fits into a socket.

The PCI bus is common in modern PCs, where it has displaced ISA and VESA Local Bus as the standard expansion bus, but it also appears in many other computer types. The bus is being succeeded by PCI Express, which launched in 2004 and offers much higher bandwidth. As of 2007 the PCI standard is still used by many legacy and new devices that do not require the higher bandwidth of PCI-E. New computers are also still provided with sample PCI slots.

The PCI specification covers the physical size of the bus (including wire spacing), electrical characteristics, bus timing, and protocols. The specification can be purchased from the PCI Special Interest Group (PCI-SIG).

Typical PCI cards used in PCs include: network cards, sound cards, modems, extra ports such as USB or serial, TV tuner cards and disk controllers. Historically video cards were typically PCI devices, but growing bandwidth requirements soon outgrew the capabilities of PCI. Today PCI video cards are uncommon and principally at the lower end of the market. However, the advent of Windows Vista with its strenuous requirements for its Aero interface, combined with many PCs lacking AGP or PCI Express slots, means that there are now many "Vista Ready" PCI graphics cards released , with a claim by one manufacturer that "In fact, what we have experienced is growing demand for PCI graphics upgrades, because the PCI card works in all PCs…Past, Present and Future."At Computex 2008, a number of cutting-edge GeForce 8 based cards were released.

Many devices traditionally provided on expansion cards are now commonly integrated onto the motherboard itself, meaning that modern PCs often have no cards fitted. However, PCI is still used for certain specialized cards, although many tasks traditionally performed by expansion cards may now be performed equally well by USB devices.

Work on PCI began at Intel's Architecture Lab circa 1990. PCI 1.0, which was merely a component-level specification, was released on June 22, 1992. PCI 2.0, which was the first to establish standards for the connector and motherboard slot, was released on April 30, 1993. PCI 2.1 was released on June 1, 1995.

PCI was immediately put to use in servers, replacing MCA and EISA as the server expansion bus of choice. In mainstream PCs, PCI was slower to replace VESA Local Bus (VLB), and did not gain significant market penetration until late 1994 in second-generation Pentium PCs. By 1996 VLB was all but extinct, and manufacturers had adopted PCI even for 486 computers. EISA continued to be used alongside PCI through 2000. Apple Computer adopted PCI for professional Power Macintosh computers (replacing NuBus) in mid-1995, and the consumer Performa product line (replacing LC PDS) in mid-1996.

Later revisions of PCI added new features and performance improvements, including a 66 MHz 3.3 V standard and 133 MHz PCI-X, and the adaptation of PCI signaling to other form factors. Both PCI-X 1.0b and PCI-X 2.0 are backward compatible with some PCI standards. With the introduction of the serial PCI Express standard in 2004, motherboard manufacturers have included progressively fewer PCI expansion slots in favor of the new standard. Although it is still common to see both interfaces implemented side-by-side, traditional PCI is likely to slowly die out in coming years.

PCI provides two separate 32-bit or 64-bit address spaces corresponding to the memory and I/O port address spaces of the x86 processor family. Addresses in these address spaces are assigned by software. A third address space, called the PCI Configuration Space, which uses a fixed addressing scheme, allows software to determine the amount of memory and I/O address space needed by each device. Each device can request up to six areas of memory space or I/O port space via its configuration space registers.

In a typical system, the firmware (or operating system) queries all PCI buses at startup time (via PCI Configuration Space) to find out what devices are present and what system resources (memory space, I/O space, interrupt lines, etc.) each needs. It then allocates the resources and tells each device what its allocation is.

The PCI configuration space also contains a small amount of device type information, which helps an operating system choose device drivers for it, or at least to have a dialogue with a user about the system configuration.

Devices may have an on-board ROM containing executable code for x86 or PA-RISC processors, an Open Firmware driver, or an EFI driver. These are typically necessary for devices used during system startup, before device drivers are loaded by the operating system.

In addition there are PCI Latency Timers that are a mechanism for PCI Bus-Mastering devices to share the PCI bus fairly. "Fair" in this case means that devices won't use such a large portion of the available PCI bus bandwidth that other devices aren't able to get needed work done. Note, this does not apply to PCIE.

"How this works is that each PCI device that can operate in bus-master mode is required to implement a timer, called the Latency Timer, that limits the time that device can hold the PCI bus. The timer starts when the device gains bus ownership, and counts down at the rate of the PCI clock. When the counter reaches zero, the device is required to release the bus. If no other devices are waiting for bus ownership, it may simply grab the bus again and transfer more data."

There is a PCI Latency Tool available, you can use a search engine to locate the latest version. This tool will allow you to change/set the latency for any PCI card that allows it. These specifications represent the most common version of PCI used in normal PCs.

• 33.33 MHz clock with synchronous transfers
• peak transfer rate of 133 MB/s (133 million bytes per second) for 32-bit bus width (33.33 MHz × 32 bits ÷ 8 bits/byte = 133 MB/s)
• peak transfer rate of 266 MB/s for 64-bit bus width
• 32-bit or 64-bit bus width
• 32-bit address space (4 gigabytes)
• 32-bit I/O port space
• 256-byte configuration space
• 5-volt signaling
• reflected-wave switching

Data and source mostly taken from Wikipedia.