Introduction
Personal Digital Assistants (PDA's) are small portable handheld computers that organize data, such as your schedule, address book, appointment calendar and to-do list. PDA's are also designed to work with your desktop PC by connecting the two devices with a serial cable. Your PDA will include software that will manage tasks on your desktop PC and synchronize tasks with your PDA.
Before you buy your PDA you need to consider a variety of factors. Do you want just a basic electronic pocket organizer with personal information management (PIM) functions? Do 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 need your PDA to take 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?
If you know how you expect to use your PDA it will help you decide what size, display type, amount of memory, operating system, handwriting software, power source and other amenities you'll need.

How big are PDA's ?
The size of a PDA can range from that of a credit card to a notebook computer. The number of features and the computing power usually increase with the size. Credit card size units typically offer only basic PIM functions and have about 512Kb of 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.
Palm size computers are the most popular PDA. In fact, many 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 PDA's also let you "write" text and include some sort of handwriting recognition software - a few even recognize spoken commands.
Larger handheld PDA's 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.

What kind of Operating Systems are available ?
Two operating systems dominate the PDA market - Microsoft's Windows CE and 3Com's Palm OS. Usually Windows CE devices have more memory and functionality. The Windows CE operating system 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 operating system tend to operate faster - starting up faster after you turn them on, running applications and finding data faster etc. 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).

What types of display are there ?
PDA's use displays that are smaller versions of those used in notebook computers, but as PDA's are small the display usually covers most of the front of the unit and is therefore the most visible feature. It's important to have a display that's as bright and legible as possible on a PDA that is within your budget. A typical palm size PDA has a resolution of 320 x 240 pixels with four shades of grey. More expensive colour 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 greyscale 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 (i) double-layer supertwist nematic (DSTN); (ii) color super-twist nematic (CSTN); (iii) High-Performance Addressing (HPA). Recent improvements in CSTN make it a great budget 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 PDA's.

How much memory does a PDA require ?
PDA's are usually supplied with 512-Kb of system RAM in credit card models and up to 16 MB in larger models. Many models also provide expansion slots for more memory.The operating system and built-in application programs are stored in ROM. To enable you to upgrade some manufacturers place the operating system in a socketed ROM module which can be removed from its socket and replaced with a new one. Other manufacturers use flash memory which can be erased and reprogrammed butbut will not erase when the power is disconnected.
Some PDA's 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 PDA's. (With an appropriate 50-to-68 pin adapter, a CompactFlash card can be used in a PCMCIA Type II slot.)
Some larger handheld PDA's 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 but most PDA's 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.

How do you transfer data from a PC to a PDA ?
The most common method for transferring data to your desktop PDA/PC is via a cable through a serial port. However, many PDA's can communicate with each other through an infrared port. These ports use the same technology as the remote control for your TV or VCR but with a higher data transfer rate (about the same rate as a parallel port). The infrared port on a PDA should conform to the IrDA standard specified by the Infrared Data Association. Any two PDA's running the same operating system, in close proximity, and in a straight line of sight to each other should be able to exchange data through their IrDA ports.

How do you write or enter text into a PDA ?
Larger PDA's have actual keyboards but medium and small PDA's require you to enter information through the touch screen with the stylus. Most systems let you tap letters on an on-screen "keyboard" or write letters on an on-screen tablet. Palm OS and Windows CE come with handwriting recognition software ie. Graffiti and Jot which allow you to print letters individually. However, you must form your letters precisely according to the software's rules, which can take some time to adjust to. Some PDA's come with 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.

What kind of power sources are available ?
More memory, CompactFlash cards, color screens, voice recording--there are many cool features and accessories for PDAs, but they need battery power to work. Most PDAs come with either alkaline batteries (usually AA size) or a rechargeable battery pack. Many also include a small backup battery to protect the memory when your main batteries run out. 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.

Can I access my email and the Internet using a PDA ?
Many PDAs are designed with the assumption that you'll check e-mail through your desktop PC and download the messages to your PDA for future reading. You can also download Web magazines, audio programs, and news subscription services if your PDA supports these features. However, some PDAs include a built-in modem or a slot where you can add one, allowing you to send and receive e-mail directly. 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.

Typical price range
At the low end are pocket organizers with some PIM functions which are little more than electronic address books. At the higher end are PDA's that look like notebook computers without disk drives and that include full size keyboards and VGA screens. Our palm size PDA's with standard functionality are in the middle and are priced between £150 to £500, with memory and display type primarily determining the cost.

Links to useful PDA resource websites
How PDA's Work
Software downloads for your PDA
PDA Support Forum

site last updated 27 August 2008