From ECDL.web

A personal digital assistant (PDA), also known as a palmtop computer, or personal data assistant, is a mobile device that functions as a personal information manager. Current PDAs often have the ability to connect to the Internet. A PDA has an electronic visual display, enabling it to include a web browser, but some newer models also have audio capabilities, enabling them to be used as mobile phones or portable media players.

The term PDA was first used on January 7, 1992 by Apple Computer CEO John Sculley, referring to the Apple Newton. In 1996, Nokia introduced the first mobile phone with full PDA functionality, the 9000 Communicator, which grew to become the world's best-selling PDA. The Communicator spawned a new category of mobile phones: the "PDA phone", now called "smartphone".

Today, almost all PDAs are smartphones. Over 150 million smartphones are sold each year, while "stand-alone" PDAs without phone functionality sell only about 3 million units per year.

[edit] Typical features

• Touch screen: 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. Touchscreen PDAs may have 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.
• Memory cards: although many early PDAs did not have memory card slots, now most have either some form of Secure Digital (SD) slot or a CompactFlash slot.
• Wired connectivity: early PDAs connected to a user's personal computer via serial ports or another proprietary connection, most of them today connect via a USB cable. PDAs are not typically able to connect to each other via USB, as USB requires one machine to act as a "host", which isn't a typical PDA function.
• Wireless connectivity: most modern PDAs have Bluetooth to connect keyboards, headsets, GPS receivers, and other nearby accessories, or other PDAs. Many modern PDAs have Wi-Fi wireless network connectivity, and can connect to Wi-Fi hotspots. Older PDAs typically had an infrared (IrDA) 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.
• Synchronization: most PDAs can synchronize their data with applications on a user's personal computer. This allows the user to update contact, schedule, or other information on their computer, 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. 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.
• Automobile navigation: 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.
• Rugged PDAs: some businesses and government organizations rely upon rugged PDAs for mobile, in-the-field data applications. These PDAs often have extra features for data capture, such as barcode readers, radio-frequency identification (RFID) readers, magnetic stripe card readers, or smart card readers.

[edit] Lists of PDAs

• Popular consumer PDAs: Acer N Series, Apple iPod touch and iPhone, BlackBerry, HP iPAQ, HTC, Palm smartphones (Pre and Pixi)
• Discontinued PDAs: Apple Newton, Atari Portfolio, Casio Pocket Viewer, iPAQ, HP Jornada Pocket PC, Palm (Tungsten E2, TX, Treo, Zire Handheld), Psion, Sony CLIÉ
• Rugged PDAs: Motorola, Psion Teklogix, Honeywell, Skeye, Trimble Navigation