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A personal digital assistant (PDA), also known as a handheld PC ,   is a variety mobile device which functions as a personal information manager. PDAs have been mostly displaced by the widespread adoption of highly capable smartphones, in particular those based on iOS and Android, seeing a rapid decline in use after 2007.  
A PDA has an electronic visual display. Most models also have audio capabilities, allowing usage as a portable media player, and also enabling many of them to be used as telephones. By the early 2000's, nearly all PDA models had the ability access the Internet, intranets or extranets via Wi-Fi or Wireless WANs, and generally include a web browser. Sometimes, instead of buttons, PDAs employ touchscreen technology.
The first PDA, the Organiser, was released in 1984 by Psion, followed by Psion's Series 3, in 1991. The latter began to resemble the more familiar PDA style, including a full keyboard.   The term PDA was first used on January 7, 1992 by Apple Inc. CEO John Sculley at the Consumer Electronics Show in Las Vegas, Nevada, referring to the Apple Newton.  In 1994, IBM introduced the first PDA with analog cellular phone functionality, the IBM Simon, which can also be considered the first smartphone. Then in 1996, Nokia introduced a PDA with digital cellphone functionality, the 9000 Communicator. Another early entrant in this market was Palm, with a line of PDA products which began in March 1996. Palm would eventually be the dominant vendor of PDAs until the rising popularity of Pocket PC devices in the early 2000s.  By the mid-2000s most PDAs had morphed into smartphones as classic PDAs without cellular radios were increasingly becoming uncommon.
A typical PDA has a touchscreen for navigation, a memory card slot for data storage, and IrDA, Bluetooth and/or Wi-Fi. However, some PDAs may not have a touchscreen, using softkeys, a directional pad, and a numeric keypad or a thumb keyboard for input. To have the functions expected of a PDA, a device's software typically includes an appointment calendar, a to-do list, an address book for contacts, a calculator, and some sort of memo (or "note") program. PDAs with wireless data connections also typically include an email client and a Web browser, and may or may not include telephony functionality.
Many of the original PDAs, such as the Apple Newton and Palm Pilot, featured a touchscreen for user interaction, having only a few buttons—usually reserved for shortcuts to often-used programs. Some touchscreen PDAs, including Windows Mobile devices, had a detachable stylus to facilitate making selections. The user interacts with the device by tapping the screen to select buttons or issue commands, or by dragging a finger (or the stylus) on the screen to make selections or scroll.
Typical methods of entering text on touchscreen PDAs include:
Despite research and development projects, end-users experience mixed results with handwriting recognition systems. Some find it frustrating and inaccurate, while others are satisfied with the quality of the recognition. 
Touchscreen PDAs intended for business use, such as the BlackBerry and Palm Treo, usually also offer full keyboards and scroll wheels or thumbwheels to facilitate data entry and navigation. Many touchscreen PDAs support some form of external keyboard as well. Specialized folding keyboards, which offer a full-sized keyboard but collapse into a compact size for transport, are available for many models. External keyboards may attach to the PDA directly, using a cable, or may use wireless technology such as infrared or Bluetooth to connect to the PDA. Newer PDAs, such as the HTC HD2, Apple iPhone, Apple iPod Touch, and Palm Pre, Palm Pre Plus, Palm Pixi, Palm Pixi Plus, Google Android (operating system) include more advanced forms of touchscreen that can register multiple touches simultaneously. These "multi-touch" displays allow for more sophisticated interfaces using various gestures entered with one or more fingers.
Although many early PDAs did not have memory card slots, now most have either some form of Secure Digital (SD) slot, a CompactFlash slot or a combination of the two. Although designed for memory, Secure Digital Input/Output (SDIO) and CompactFlash cards are available that provide accessories like Wi-Fi or digital cameras, if the device can support them. Some PDAs also have a USB port, mainly for USB flash drives.[ dubious ] Some PDAs use microSD cards, which are electronically compatible with SD cards, but have a much smaller physical size.
While early PDAs connected to a user's personal computer via serial ports or another proprietary connection,[ specify ] many today connect via a USB cable. Older PDAs were unable to connect to each other via USB, as their implementations of USB didn't support acting as the "host". Some early PDAs were able to connect to the Internet indirectly by means of an external modem connected via the PDA's serial port or "sync" connector,  or directly by using an expansion card that provided an Ethernet port.
Most PDAs utilize Bluetooth, a popular wireless protocol for mobile devices. Bluetooth can be used to connect keyboards, headsets, GPS receivers, and other nearby accessories. It's also possible to transfer files between PDAs that have Bluetooth. Many PDAs have Wi-Fi wireless network connectivity and can connect to Wi-Fi hotspots.  All smartphones, and some other PDAs, can connect to Wireless Wide Area Networks, such as those provided by cellular telecommunications companies. Older PDAs from the 1990s to 2006 typically had an IrDA (infrared) port allowing short-range, line-of-sight wireless communication. Few current models use this technology, as it has been supplanted by Bluetooth and Wi-Fi. IrDA allows communication between two PDAs, or between a PDA and any device with an IrDA port or adapter. Some printers have IrDA receivers,  allowing IrDA-equipped PDAs to print to them, if the PDA's operating system supports it. Universal PDA keyboards designed for these older PDAs use infrared technology.[ citation needed ] Infrared technology is low-cost and has the advantage of being allowed aboard.[ specify ]
Most PDAs can synchronize their data with applications on a user's computer. This allows the user to update contact, schedule, or other information on their computer, using software such as Microsoft Outlook or ACT!, and have that same data transferred to PDA—or transfer updated information from the PDA back to the computer. This eliminates the need for the user to update their data in two places. Synchronization also prevents the loss of information stored on the device if it is lost, stolen, or destroyed. When the PDA is repaired or replaced, it can be "re-synced" with the computer, restoring the user's data. Some users find that data input is quicker on their computer than on their PDA, since text input via a touchscreen or small-scale keyboard is slower than a full-size keyboard. Transferring data to a PDA via the computer is therefore a lot quicker than having to manually input all data on the handheld device.[ citation needed ]
Most PDAs come with the ability to synchronize to a computer. This is done through synchronization software provided with the handheld, or sometime with the computer's operating system. Examples of synchronization software include:
These programs allow the PDA to be synchronized with a personal information manager, which may be part of the computer's operating system, provided with the PDA, or sold separately by a third party. For example, the RIM BlackBerry comes with RIM's Desktop Manager program, which can synchronize to both Microsoft Outlook and ACT!. Other PDAs come only with their own proprietary software. For example, some early Palm OS PDAs came only with Palm Desktop, while later Palm PDAs—such as the Treo 650—have the ability to sync to Palm Desktop or Microsoft Outlook. Microsoft's ActiveSync and Windows Mobile Device Center only synchronize with Microsoft Outlook or a Microsoft Exchange server.[ citation needed ] Third-party synchronization software is also available for some PDAs from companies like CommonTime  and CompanionLink.  Third-party software can be used to synchronize PDAs to other personal information managers that are not supported by the PDA manufacturers (for example, GoldMine and IBM Lotus Notes).
Some PDAs can synchronize some or all of their data using their wireless networking capabilities, rather than having to be directly connected to a personal computer via a cable. Devices running Palm's webOS or Google's Android operating system primarily sync with the cloud. For example, if Gmail is used, information in contacts, email, and calendar can be synchronized between the PDA and Google's servers. RIM sells BlackBerry Enterprise Server to corporations so that corporate BlackBerry users can wirelessly synchronize their PDAs with the company's Microsoft Exchange Server, IBM Lotus Domino, or Novell GroupWise servers.  Email, calendar entries, contacts, tasks, and memos kept on the company's server are automatically synchronized with the BlackBerry. 
The most common operating systems pre-installed on PDAs are:
Other, rarely used operating systems:
Some PDAs include Global Positioning System (GPS) receivers; this is particularly true of smartphones. Other PDAs are compatible with external GPS-receiver add-ons that use the PDA's processor and screen to display location information.  PDAs with GPS functionality can be used for automotive navigation. PDAs are increasingly being fitted as standard on new cars. PDA-based GPS can also display traffic conditions, perform dynamic routing, and show known locations of roadside mobile radar guns. TomTom, Garmin, and iGO offer GPS navigation software for PDAs.
Some businesses and government organizations rely upon rugged PDAs, sometimes known as enterprise digital assistants (EDAs) or mobile computers, for mobile data applications. These PDAs have features that make them more robust and able to handle inclement weather, jolts and moisture. EDAs often have extra features for data capture, such as barcode readers, radio-frequency identification (RFID) readers, magnetic stripe card readers, or smart card readers. These features are designed to facilitate the use of these devices to scan in product or item codes.
Typical applications include:
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PDAs and handheld devices are allowed in many classrooms for digital note-taking. Students can spell-check, modify, and amend their class notes on a PDA. Some educators[ who? ] distribute course material through the Internet or infrared file-sharing functions of the PDA. Textbook publishers have begun to release e-books, which can be uploaded directly to a PDA, reducing the number of textbooks students must carry.  Brighton and SUSSEX Medical School in the UK was the first medical school to provide wide scale use of PDAs to its undergraduate students. The learning opportunities provided by having PDAs complete with a suite of key medical texts was studied with results showing that learning occurred in context with timely access to key facts and through consolidation of knowledge via repetition. The PDA was an important addition to the learning ecology rather than a replacement.  Software companies have developed PDA programs to meet the instructional needs of educational institutions, such as dictionaries, thesauri, word processing software, encyclopedias, webinar and digital lesson planners.
PDAs may be used by music enthusiasts to play a variety of music file formats. Many PDAs include the functionality of an MP3 player. Road rally enthusiasts can use PDAs to calculate distance, speed, and time. This information may be used for navigation, or the PDA's GPS functions can be used for navigation. Underwater divers can use PDAs to plan breathing gas mixtures and decompression schedules using software such as "V-Planner".
The Sony CLIÉ is a series of personal digital assistants (PDAs) running the operating system (OS) Palm OS, developed and marketed by Sony from 2000 to 2005. The devices introduced many new features to the PDA market, such as a jog dial interface, high-resolution displays, and Sony technologies like Memory Stick slots and ATRAC3 audio playback. Most models were designed and manufactured in Japan. The name was initially an attempt at a new coinage term, though it means tool in the Jèrriais language.
Palm OS was a mobile operating system initially developed by Palm, Inc., for personal digital assistants (PDAs) in 1996. Palm OS was designed for ease of use with a touchscreen-based graphical user interface. It is provided with a suite of basic applications for personal information management. Later versions of the OS have been extended to support smartphones. The software appeared on the company's line of Palm devices while several other licensees have manufactured devices powered by Palm OS.
Psion PLC was a designer and manufacturer of mobile handheld computers for commercial and industrial uses. The company was headquartered in London, England, with major operations in Mississauga, Ontario, Canada, and other company offices in Europe, the United States, Asia, Latin America, and the Middle East. It was a public company listed on the London Stock Exchange and was once a constituent of the FTSE 100 Index.
A Pocket PC is a class of personal digital assistant (PDA) that runs the Windows Mobile or Windows Embedded Compact operating system that has some of the abilities of modern desktop PCs. The name was introduced by Microsoft in 2000 as a rebranding of the Palm-size PC category. Some of these devices also had integrated phone and data capabilities, which were called Pocket PC Phone Edition or simply "Smartphone".
Palm was a line of personal digital assistants (PDAs) and mobile phones developed by California-based Palm, Inc., originally called Palm Computing, Inc. Palm devices are often remembered as "the first wildly popular handheld computers," responsible for ushering in the smartphone era.
A smartphone is a portable computer device that combines mobile telephone functions and computing functions into one unit. They are distinguished from older-design feature phones by their stronger hardware capabilities and extensive mobile operating systems, which facilitate wider software, access to the internet, and multimedia functionality, alongside core phone functions such as voice calls and text messaging. Smartphones typically contain a number of metal–oxide–semiconductor (MOS) integrated circuit (IC) chips, include various sensors that can be leveraged by pre-installed and third-party software, and support wireless communication protocols. More recently, smartphone manufacturers have begun to integrate satellite messaging connectivity and satellite emergency services into devices for use in remote regions where there is no reliable cellular network.
The Psion Series 5 was a personal digital assistant (PDA) from Psion. It came in two main variants, the Series 5 and the Series 5mx (1999), the latter having a faster processor, clearer liquid crystal display (LCD), and updated software. There was also a rare Series 5mx Pro, which differed only in having the operating system (OS) loaded into random-access memory (RAM) and hence upgradeable. Ericsson marketed a version of the Series 5mx renamed as MC218.
A mobile device is a computer small enough to hold and operate in the hand. Mobile devices typically have a flat LCD or OLED screen, a touchscreen interface, and digital or physical buttons. They may also have a physical keyboard. Many such devices can connect to the Internet and connect with other devices such as car entertainment systems or headsets via Wi-Fi, Bluetooth, cellular networks or near field communication. Integrated cameras, the ability to place and receive voice and video telephone calls, video games, and Global Positioning System (GPS) capabilities are common. Power is typically provided by a lithium-ion battery. Mobile devices may run mobile operating systems that allow third-party applications to be installed and run.
The Tungsten series was Palm, Inc.'s line of business-class Palm OS-based PDAs.
Windows Mobile was a family of mobile operating systems developed by Microsoft for smartphones and personal digital assistants.
ActiveSync is a mobile data synchronization app developed by Microsoft, originally released in 1996. It synchronizes data with handheld devices and desktop computers. In the Windows Task Manager, the associated process is called wcescomm.exe.
The Z22 was one of the first of Palm, Inc.'s handhelds to be released under the new "Palm" brand, and the first to be released without the "Zire" moniker. Released on October 12, 2005, it replaced the monochrome Zire 21, and was priced at $99 USD. The Palm Z22 came with Palm OS Garnet 5.4.9 preloaded and is not upgradable. It featured a 200 MHz Samsung S3C2410 ARM processor developed around the 32-bit ARM920T core that implements the ARMv4T architecture. The Z22 ran on a li-ion battery that had a life of about 8 hours depending on usage.
Push email is an email system that provides an always-on capability, in which new email is actively transferred (pushed) as it arrives by the mail delivery agent (MDA) to the mail user agent (MUA), also called the email client. Email clients include smartphones and, less strictly, IMAP personal computer mail applications.
The Motorola A780 is the second cellular PDA running the Linux operating system.
iQue was a line personal digital assistants (PDA) with integrated Global Positioning System (GPS) receivers sold by Garmin. It was introduced in 2003 and discontinued in mid-2008.
A tablet computer, commonly shortened to tablet, is a mobile device, typically with a mobile operating system and touchscreen display processing circuitry, and a rechargeable battery in a single, thin and flat package. Tablets, being computers, do what other personal computers do, but lack some input/output (I/O) abilities that others have. Modern tablets largely resemble modern smartphones, the only differences being that tablets are relatively larger than smartphones, with screens 7 inches (18 cm) or larger, measured diagonally, and may not support access to a cellular network. Unlike laptops, tablets usually run mobile operating systems, alongside smartphones.
The Palm Pre, styled as palm prē, is a multitasking smartphone that was designed and marketed by Palm with a multi-touch screen and a sliding keyboard. The smartphone was the first to use Palm's Linux-based mobile operating system, webOS. The Pre functions as a camera phone and a portable media player, and has location and navigation capabilities. The Pre also serves as a personal information manager, has a number of communication and collaboration applications, and has Bluetooth and Wi-Fi connectivity built-in.
An app store is a type of digital distribution platform for computer software called applications, often in a mobile context. Apps provide a specific set of functions which, by definition, do not include the running of the computer itself. Complex software designed for use on a personal computer, for example, may have a related app designed for use on a mobile device. Today apps are normally designed to run on a specific operating system—such as the contemporary iOS, macOS, Windows, Linux or Android—but in the past mobile carriers had their own portals for apps and related media content.
Pocket PC 2000 was the first member of the Windows Mobile family of mobile operating systems that was released on April 19, 2000, and was based on Windows CE 3.0. It is the successor to the operating system aboard Palm-size PCs. Backwards compatibility was retained with such Palm-size PC applications.
Pocket-sized computer describes the post-programmable calculator / pre-smartphone pocket-sized portable-office hardware devices that included the earlier DOS-based palmtops and subsequent Windows-CE handhelds, as well as a few other terms, primarily covering the 1980s through 2007.