Personal digital assistants (PDAs) are handheld computers, but have become much more versatile over the years. PDAs are also known as pocket computers or palmtop computers. PDAs have many uses: calculation, use as a clock and calendar, accessing the Internet, sending and receiving E-mails, video recording, typewriting and word processing, use as an address book, making and writing on spreadsheets, scanning bar codes, use as a radio or stereo, playing computer games, recording survey responses, and Global Positioning System (GPS). Newer PDAs also have both color screens and audio capabilities, enabling them to be used as mobile phones (smartphones), web browsers, or portable media players. Many PDAs can access the Internet, intranets or extranets via Wi-Fi, or Wireless Wide-Area Networks (WWANs). Many PDA's employ touch screen technology.

History

The term "personal data assistant" was on January 7, 1992 by Apple Computer CEO John Sculley at the Consumer Electronics Show in Las Vegas, Nevada, referring to the Apple Newton. PDAs are sometimes referred to as "Palms", "Palm Pilot" or "Palm Tops"

Typical Features

Currently, a typical PDA has a touch screen for entering data, a memory card slot for data storage and at least one of the following for connectivity: IrDA, Bluetooth and/or WiFi. However, many PDAs (typically those used primarily as telephones) may not have a touch screen, using softkeys, a directional pad and either the numeric keypad or a thumb keyboard for input.

Software typically required to be a PDA includes an appointment calendar, a to-do list, an address book for contacts and some sort of note program. Connected PDAs also typically include E-mail and Web support

Touch screen

Many original PDAs, such as the Apple Newton and the Palm Pilot, featured touch screens for user interaction, having only a few buttons usually reserved for shortcuts to often used programs. Touch screen PDAs, including Windows Pocket PC devices, usually have a detachable stylus that can be used on the touch screen. Interaction is then done by tapping the screen to activate buttons or menu choices, and dragging the stylus to, for example, highlight. Text input is usually done in one of two ways:

• Using a virtual keyboard, where a keyboard is shown on the touch screen. Input is done by tapping the letters.

• Using letter or word recognition, where letters or words are written on the touch screen, and then "translated" to letters in the currently activated text field. Despite rigorous research and development projects, end-users experience mixed results with this input method, with some finding it frustrating and inaccurate, while others are satisfied with the quality.[1] Recognition and computation of handwritten horizontal and vertical formulas such as "1 + 2 =" was also under development.

PDAs for business use, including the BlackBerry and Treo, have full keyboards and scroll wheels or thumb wheels to facilitate data entry and navigation, in addition to supporting touch-screen input. There are also full-size foldable keyboards available that plug directly, or use wireless technology to interface with the PDA and allow for normal typing. BlackBerry also has additional functionality as push based email and applications.

Newer PDAs, such as the Apple iPhone include new user interfaces using other means of input. The iPhone uses a technology called Multi-touch.

Memory cards

Although many early PDAs did not have memory card slots, now most have either an SD (Secure Digital) and/or a Compact Flash slot. Although originally designed for memory, SDIO and Compact Flash cards are available for such things as Wi-Fi and Webcams. Some PDAs also have a USB port, mainly for USB flash drives.

As more PDAs include telephone support, to keep the size down, many now offer miniSD or microSD slots instead of full-sized SD slots

Wired connectivity

While many earlier PDAs connected via serial ports or other proprietary format, many today connect via USB cable. This served primarily to connect to a computer, and few, if any PDAs were able to connect to each other out of the box using cables, as USB requires one machine to act as a host - functionality which was not often planned. Some PDAs were able to connect to the internet, either by means of one of these cables, or by using an extension card with an ethernet port/RJ-45 adaptor

Wireless connectivity

Most modern PDAs have Bluetooth wireless connectivity, an increasingly popular tool for mobile devices. It can be used to connect keyboards, headsets, GPS and many other accessories, as well as sending files between PDAs. Many mid-range and superior PDAs have Wi-Fi/WLAN/802.11-connectivity, used for connecting to Wi-Fi hotspots or wireless networks. Older PDAs predominantly have an IrDA (infrared) port; however fewer current models have the technology, as it is slowly being phased out due to support for Bluetooth and Wi-Fi. IrDA allows communication between two PDAs: a PDA and any device with an IrDA port or adapter. Most universal PDA keyboards use infrared technology because many older PDAs have it, and infrared technology is low-cost.

Synchronization

An important function of PDAs is synchronizing data with a PC. This allows up-to-date contact information stored on software such as Microsoft Outlook or ACT! to update the database on the PDA. The data synchronization ensures that the PDA has an accurate list of contacts, appointments and e-mail, allowing users to access the same information on the PDA as the host computer.

The synchronizing also prevents the loss of information stored on the device in case it is lost, stolen, or destroyed. Another advantage is that data input is usually a lot quicker on a PC, since text input via a touch screen is still not quite optimal. Transferring data to a PDA via the computer is therefore a lot quicker than having to manually input all data on the handheld device.

Most PDAs come with the ability to synchronize to a PC. This is done through synchronization software provided with the handheld, such as HotSync Manager, which comes with Palm OS handhelds, Microsoft ActiveSync for older versions of Windows or Windows Mobile Device Center on Windows Vista, which comes with Windows Mobile handhelds.

These programs allow the PDA to be synchronized with a Personal information manager. This personal information manager may be an outside program or a proprietary program. For example, the BlackBerry PDA comes with the 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 Palms such as the Treo 650 has the built-in ability to sync to Palm Desktop and/or Microsoft Outlook, while Microsoft's ActiveSync and Windows Mobile Device Center only synchronize with Microsoft Outlook or a Microsoft Exchange server.

Third-party synchronization software is also available for many PDAs from companies like Intellisync and CompanionLink. This software synchronizes these handhelds to other personal information managers which are not supported by the PDA manufacturers, such as GoldMine and Lotus Notes.

Customization

As with personal computers, it is possible to install additional software on most PDAs. Software can be bought or downloaded from the Internet, allowing users to personalize their PDAs to their liking. An example of this would be the display theme for the PDA. Almost all PDAs also allow for adding some form of hardware. The most common is a memory card slot, which allows the users to get additional and exchangeable storage space on their handheld devices. There are also miniature keyboards that can be connected to most mainstream PDAs for quicker text input. PDAs with Bluetooth use Bluetooth-enabled devices like headsets, mice and (possibly foldable) keyboards.

Medical and scientific uses

In medicine, PDAs have been shown to aid diagnosis and drug selection and some studies have concluded that their use by patients to record symptoms improves the effectiveness of communication with hospitals during follow-up. The first landmark study in testing the effectiveness of PDAs in a medical setting was conducted at the Brigham & Women's Hospital and Massachusetts General Hospitals in affiliation with Harvard Medical School. Led by the team of Steven Labkoff, MD and Sandeep Shah, the Constellation project used Apple's Newton (first PDA in the market) to cater to the demands of the medical professionals.

Constellation's objective was to test how clinicians in various medical environments (wired vs un wired) would use medical reference books on a hand-held device. The study validated the hypothesis that PDAs with medical content would be used to a greater degree (>40% more often) in unwired environments.

Today, the company evolved from the effort Skyscape offers a wide range of resources including drug information, treatment options, guidelines, evidence based information and journal summaries including the drug & safety alerts. Other entrants include Epocrates and ABX guide, which supply drug databases, treatment information and relevant news in formats specific to mobile devices and services such as AvantGo translate medical journals into readable formats and provide updates from journals. WardWatch organizes medical records to remind doctors making ward rounds of information such as the treatment regimens of patients and programs. Finally, Pendragon and Syware provide tools for conducting research with mobile devices, and connecting to a central server allowing the user to enter data into a centralized database using their PDA. Additionally, Microsoft Visual Studio and Sun Java provide programming tools for developing survey instruments on the handheld. These development tools allow for integration with SQL databases that are stored on the handheld and can be synchronized with a desktop/server based database. Recently the development of Sensor Web technology has led to discussion of using wearable bodily sensors to monitor ongoing conditions like diabetes and epilepsy and alerting medical staff or the patient themselves to the treatment required via communication between the web and PDAs.

Operating system

The currently major PDA operating systems are:

• Palm OS - owned by PalmSource

• Windows Mobile Professional and Classic for use on Pocket PCs, (based on the Windows CE kernel) - owned by Microsoft

• BlackBerry OS - owned by Research In Motion

• Many operating systems based on the Linux kernel - free (not owned by any company) These include

o Familiar (comes in three flavours: GPE, Opie and barebone)
o OpenZaurus (for Zaurus PDAs)
o Intimate (for PDAs with an exceedingly large amount of memory)

• Symbian OS (formerly EPOC) owned by Motorola, Panasonic, Nokia, Samsung, Siemens and Sony Ericsson