Personal digital assistants (PDAs) are hand-held computers equipped with operating system and applications software. PDAs can be equipped with communications capabilities for short-text messaging, e-mail, news updates, Web surfing, voice mail, and Internet telephony. Today’s PDAs also can act as MP3 players, voice recorders, and digital cameras with the addition of multimedia modules.

Some PDAs can even accommodate a module that provides location information via the Global Positioning System (GPS). PDAs are intended for mobile users who require instant access to information regardless of their location at any given time. The Newton MessagePad, introduced by Apple Computer in 1993, was the first true PDA.

Trumpeted as a major milestone of the information age, the MessagePad was soon joined by similar products from such companies as Hewlett- Packard, Motorola, Sharp, and Sony. These early hand-held devices were hampered by poor performance, excessive weight, and unstable software. Without a wireless communications infrastructure, there was no compelling advantage of owning a PDA.

With the performance limitations largely corrected and the emergence of new wireless PCS—plus continuing advances in operating systems, connectivity options, and battery technology—PDAs are now well on the way toward fulfilling their potential.

Applications

Real estate agents, medical professionals, field service technicians, and delivery people are just a few of the people using PDAs. Real estate agents can use PDAs to conveniently browse through property listings at client locations. Health care professionals can use PDAs to improve their ability to access, collect, and record patient information at the point of care.

Numerous retailers and distributors can collect inventory data on the store and warehouse floor and later export tose data into a spreadsheet on a PC. Insurance agents, auditors, and inspectors can use PDAs to record data in the field and then instantly transfer those data to PCs and databases at the home office.

For professionals who tote around a laptop computer to give presentations with Microsoft PowerPoint, there is a module for the Springboard Visor that connects the device directly to digital projectors (or other VGAdisplays) with an interface cable. The user downloads the presentation material from a PC to the Visor and then taps an icon displayed on the Visor screen to start the 1024 × 768 resolution color presentation. The user can even control the presentation from anywhere in the room using the product’s infrared remote control.

PDA Components

A side from the case, PDA components include a screen, keypad, or other type of input device; an operating system; memory; and battery. Many PDAs can be outfitted with fax/modem cards and a docking station to facilitate direct connection to a PC or LAN for data transfers and file synchronization. Some PDAs, such as Palm Computing’s Palm VII, have a wireless capability that allows information retrieval from the Internet.

Of course, PDAs run numerous applications to help users stay organized and productive. Some PDAs have integral 56-kbps modems and serial ports that allow them to be attached via cable to other devices. Aunique PDAis Handspring’s Visor, which uses the Palm OS operating system.

What makes the Visor unique is that it is expandable via an external expansion slot called a Springboard. In addition to backup storage and flash storage modules, the slot lets users add software and hardware modules that completely change the function of the Visor. Springboard modules allow the Visor to become an MP3 player, pager, modem, GPS receiver, e-book, or video game device.

Display The biggest limitation of PDAs is the size of their screens. Visibility is greatly improved through the use of nonglare screens and backlighting, which aid viewing and entering information in any lighting condition. In a dim indoor environment, backlighting is a virtual necessity, but it drains the battery faster. Some PDAs offer user-controllable backlighting, while others let the user set a timer that shuts off the screen automatically after the unit has been idle for a specified period of time. Both features greatly extend battery life. Other PDAs, such as the Visor Prism, feature an active-matrix backlit display capable of displaying over 65,000 colors.

Keyboard Some PDAs have on-screen keyboards, but they are too small to permit touch typing. The use of a stylus speeds up text input and makes task selection easier. Of course, the instrument can be used for handwritten notes. The PDA’s handwriting-recognition capability enables the notes to be stored as text for use by various applications, such as a date book, address book, and to-do list. As an option, foldout full-size keyboards are available that attach to the PDA. They weigh only 8 ounces, making it much easier to respond to e-mail, compose memos, and take notes without having to lug around a laptop.

Operating Systems A PDA ’s operating system provides the foundation on which applications run. The operating system may offer handwriting recognition, for example, and include solutions for organizing and communicating information via fax or electronic mail, as well as the ability to integrate with Windows and Mac OS-based computers in enterprise environments.

The operating system also may include built-in support for a range of modems and third-party paging and cellular communication solutions. Because memory is limited in a PDA, usually between 2 and 64 MB, the operating system and the applications that run on it must be compact. Some operating systems come with useful utilities. There are utilities that set up direct connections between the PDA and desktop applications to transfer files between them via a cable or infrared connection.

A synchronization utility ensures that the user is working from the latest version of a file. Some operating systems offer tools called “intelligent agents” that automate routine tasks. An intelligent agent can be programmed to set up a connection to the Internet, for example, and check for e-mail. To activate this process, the user might only have to touch an icon on the PDA’s screen with a pen.

There are two major operating systems in use today— Microsoft’s Pocket PC platform and the Palm OS. Pocket PC’s predecessor, Windows CE, was too difficult to use and not powerful enough to draw users away from the popular Palm OS. But the Pocket PC’s redesigned interface overcomes most of Windows CE’s previous problems. The Pocket PC platform is a version of Windows that preserves the familiarity of the Windows-based desktop and integrates seamlessly with Outlook, Word, and Excel.

The platform includes a version of Internet Explorer for browsing the Web over a wireless connection or ordinary phone line and Windows Media Player for listening to digital music and watching digital videos. It also includes Microsoft Reader for reading e-books downloaded from the Internet. Palm OS is a more efficient operating system than Pocket PC. Consequently, it requires less processing power and less memory than equivalent products using the Pocket PC operating system.

Memory Although PDAs come with a base of applications built into ROM—usually a file manager, word processor, and scheduler—users can install other applications as well. New applications and data are stored in RAM. At a minimum, PDAs come with only 2 MB, while others offer up to 64 MB. When equipped with 2 MB of memory, the PDAcan store approximately 6000 addresses, 5 years of appointments, 1500 to-do items, and 1500 memos.

Some PDAs have a PC card (formerly PCMCIA) slot that can accommodate storage cards that are purchased separately. Even though many Pocket PC products come in higher memory configurations, an 8-MB Palm OS product can store as much or even more information than a 16-MB Pocket PC product with little performance degradation.

The better performance is due to the efficiencies of the Palm OS, which uses less memory and processing power than equivalent products based on Pocket PC. Since greater memory capacity increases the overall price of the product, vendors like Handspring believe that 8 MB offers the most utility at the most competitive price.

Power Many PDAs use ordinary AAA alkaline batteries. Manufacturers claim a battery life of 45 hours when users search for data 5 minutes out of every hour the unit is turned on. Of course, using the backlight display will drain the batteries much faster. Using the backlight will reduce battery life by about 22 percent. Other power sources commonly used with PDAs include an ac adapter and rechargeable lithium-ion battery.

The rechargeable battery offers more flexible power management in a smaller space. The components that operate the color screen increase the power draw from the battery. With AAA batteries, the user would have to replace them rather frequently. The rechargeable battery solution enhances the user’s experience by providing full power in a pocket-sized package. Lithium-ion rechargeable batteries offer 2 hours of continuous use.

Fax/Modems Some PDAs come with an external fax/modem to support basic messaging needs when hooked up to a telephone line. Others offer a PC card slot (formerly PCMCIA) that can accept not only fax/modems but also storage cards. With fax/modems, PDAusers can receive a fax from their office, annotate it, and fax it back with comments written on it in “electronic ink.”

There are wireless Ethernet modules available that allow the user to roam about the workplace or campus with secure connections, peer-to-peer links between devices, and highspeed access to the Internet, e-mail, and network resources. Transmissions of up to 11 Mbps are possible, but actual throughput is determined by the speed of the PDA’s processor.

The modules adhere to the IEEE 802.11b high-rate standard for wireless LANs and support 40- or 128-bit Wired-Equivalent Privacy (WEP) encryption. Transmission ranges of up to 1000 feet (300 meters) in open environments and 300 feet (90 meters) in office environments are supported.

Cradle A cradle allows the PDAto connect to a desktop PC via a standard serial cable or USB cable. The user simply drops the PDAinto the cradle and presses a button to automatically synchronize desktop files with those held in the PDA. An alternative to cable is an infrared (IR) connection.

With an IR-enabled PDA, users not only can swap and synchronize files with a PC but also can beam business cards, phone lists, memos, and add-on applications to other IRenabled PDAs. IR-enabled PDAs also can use third-party beaming applications with IR-enabled phones, printers, and other devices.

Improvements in technology and the availability of wireless communications services, including PCS, overcome many of the limitations of early PDAproducts, making today’s handheld devices very attractive to mobile professionals. In the process, PDAs are finding acceptance beyond vertical markets and finally becoming popular among consumers, particularly those looking for an alternative to notebook computers and younger people who want a versatile device from which they also can play MP3 music files and games as well as read e-books.