by Amazon.com Need information on the go? Keep yourself informed, organized, and entertained with a personal digital assistant (PDA). PDAs are mobile computers that manage your calendar, contact information, and to-do lists. Some provide a voice recorder and note taker, and others even let you read e-mail and information downloaded from the Internet.
Overview PDAs are usually designed to work with your desktop PC. First, you connect the two devices with a serial cable. Then you use the PDA's included software to manage tasks on your desktop PC and to synchronize tasks with the PDA. When shopping for a PDA, start by identifying your needs. Do you want just a basic electronic pocket organizer with personal information management (PIM) functions? Will you need to coordinate your information with others who are connected through a network? Will you need to download e-mail and other information from the Internet to your PDA? Will you use your PDA to jot down notes during meetings? Will you need a larger PDA with a bigger screen and more memory, or will you want to travel with your PDA in your pocket? Knowing what tasks you'll use your PDA for will help you decide what body size, display type, memory, operating system, handwriting software, power source, and other amenities you'll need.
PDA body sizes Credit-card-size units typically offer only basic PIM functions and have about 512-KB RAM. Because the units are so small, the screen may be difficult to read, and there's little room for buttons, so entering data can be tedious or require you to connect to a desktop PC and to use the PC's keyboard. Still, these PDAs can sound an alarm before your appointments and keep track of your business contacts, addresses, and phone numbers in a tiny, convenient package. Palm-size computers are the most popular PDA body style. In fact, may people consider "PDA" and "palm computer" to be synonymous. Smaller than a paperback but larger than a deck of cards, palm computers fit easily in the palm of your hand. The units are too small to include a keyboard, so you enter commands and data by pressing surface-mounted buttons or by tapping the display with a stylus. Most PDAs also let you "write" text and include some sort of handwriting recognition software; a few recognize spoken commands. Larger handheld PDAs range in size from a thick checkbook to a small notebook computer. These units have room for more memory and expansion slots, a half-height or even full-size VGA display, and a keyboard with touch-type capabilities. With increased size, you get increased computing power and versatility, but you lose the advantages of pocket portability. These larger units also usually cost more than smaller ones.
Operating system platforms In general, Windows CE devices have more memory and functionality. The Windows CE OS comes with a large set of standard applications, and its interface uses a variation of the familiar Windows desktop. The standard applications are Microsoft Pocket Outlook, which includes Calendar, Contacts, Tasks, and Inbox (which sends and receives e-mail); ActiveSync, which synchronizes data with your PC; Calculator; Channels, which downloads information from the Internet; Connections, which provides Internet access and communications; Note Taker; PC Link; Solitaire; and Voice Recorder. The PDA manufacturer may add other applications as well. Devices based on 3Com's Palm OS tend to operate faster--starting up faster after you turn them on, running applications and finding data faster, and so on. They have a reputation for being easy to set up, learn, and use, and have a much longer battery life. They are also known for their popular PIM applications and extensive support from third-party developers, with thousands of software, shareware, and freeware titles to choose from. The PIM applications include Date Book, Address Book, Mail, To-Do List, Memo Pad, Expense, and Calculator, along with Security, Games, and HotSync technology (synchronizes data with your PC).
Display types A typical palm-size PDA has a resolution of 320 x 240 pixels with four shades of gray; more expensive color models offer 256 colors. Nearly all PDAs have a liquid crystal display (LCD), backlit touch-screen with a stylus for tapping commands, selecting items, and writing text. Monochrome LCD is the least expensive and most energy-efficient choice, providing grayscale images and text. Passive-matrix is a type of LCD color display on mid-level units that provides good color images when you view it straight on. There are three types of passive-matrix displays: double-layer supertwist nematic (DSTN), color super-twist nematic (CSTN), and High-Performance Addressing (HPA). Recent improvements in CSTN make it a great low-cost alternative to active-matrix. Active-matrix, also called "thin film transistor" (TFT), is the brightest, sharpest, clearest, and most expensive type of LCD flat panel display that is practical for PDAs.
Memory The operating system and built-in application programs are stored in ROM. For upgrading purposes, some manufacturers place the operating system in a socketed ROM module--a module you can remove from its socket and replace with a new one. Other manufacturers use flash memory--a type of memory that can be erased and reprogrammed but that doesn't erase when the power is disconnected. Some PDAs include slots for CompactFlash cards. These 50-pin cards are similar in function to, but much smaller than, the 68-pin PCMCIA PC cards that are so popular in laptop and notebook computers. CompactFlash cards provide up to 96 MB (and growing) of data storage, but their small, light, energy-efficient design make them ideal for PDAs. (With an appropriate 50-to-68 pin adapter, a CompactFlash card can be used in a PCMCIA Type II slot.) Finally, some larger handheld PDAs include PCMCIA slots for PCMCIA cards. There are three types of PCMCIA cards and slots: Type I, Type II, and Type III. Type I cards are 3.3 millimeters thick and are used mostly as additional ROM or RAM. Type II cards are 5.5 millimeters thick and used mostly as modems. Type III cards are 10.5 millimeters thick and used mostly as virtual disk drives; however, most PDAs are not large enough to accommodate these. A Type I slot holds one Type I card; a Type II slot holds one Type II card or two Type I cards. A Type III slot holds one Type III card or one Type I and one Type II card.
Infrared transceiver port
Text entry and handwriting
recognition Other PDAs may come with, or may permit you to buy and install, natural handwriting recognition software. Instead of following the software's rules for writing letters, you train the software to recognize your own handwriting. The advantage is that you don't have to learn the PDA's writing rules; the disadvantage is that natural handwriting recognition is less accurate, although the accuracy may improve with training.
Power supply and batteries One set of alkaline batteries usually lasts a few weeks with normal use; rechargeable battery packs typically last several hours between charges. And not by coincidence, the PDAs that come with rechargeable battery packs usually consume more power than those that come with only alkaline batteries. Many PDAs have power-management settings to help the batteries last longer. For example, you can set the backlight or the PDA itself to turn off after a few minutes of idle time. The most common types of rechargeable battery packs are nickel cadmium (NiCad), nickel metal hydride (NiMH), and lithium ion. A larger PDA may have a smart battery pack that provides the PDA with information about its power status so that the PDA can conserve power intelligently.
E-mail and Internet access Setting up a PDA to work with an Internet Service Provider's (ISP) e-mail server can be a tedious, time-consuming process--especially if you've never done it before--but you should only have to do it once. One reason for the added time and complication is that the communication software on many PDAs is less sophisticated and has fewer automatic setup conveniences than the corresponding software on desktop PCs. Before setting up the PDA, you need your e-mail address, password, ISP's dial-up telephone number, and the following information about your e-mail system: your protocol to receive e-mail; your incoming-mail server name; your outgoing-mail server name; and your primary and secondary DNS name server addresses. You may also need to know if your ISP wants you to use IP header compression or to enable software compression. You can find this information on your ISP's Web site or by contacting its customer service department. Among the PDAs that support e-mail directly, most work with POP3, IMAP4, SMTP, and LDAP protocols, with POP3 being the most common. Larger PDAs based on Windows CE may include Pocket Internet Explorer, a slimmer version of Microsoft Internet Explorer. Tapping your stylus on a touch screen that's running Pocket Internet Explorer is a convenient and fun way to surf the Web, but don't expect to watch streaming videos or to listen to sound clips; these functions are not yet supported.
Price range
~Mike Brown is a consumer electronics editor for Amazon.com, covering phones, PDAs, printers, scanners, and other products.
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