More than 9 million personal digital assistants have been sold.
You have been carrying around your big notebook/organizer that has your address book, daily planner, to-do lists, memo pads, calendar, project lists and expense reports -- everything that you need to keep your life organized. It's bulky, heavy and stuffed full, but if you don't have it, you're lost. But as you jot down appointments on your calendar or look up phone numbers in your address book, you see other people everywhere -- in business meetings, at the airport, around the supermarket -- scribbling things on a device that is about the size of a small calculator or maybe the size of a paperback book. They have traded their calendars and address books for a personal digital assistant, or PDA, a remarkable, tiny, fully functional computer that you can hold in one hand. And unlike that paper organizer, a PDA can hold your downloaded e-mail and play music.

PDAs are the one of the fastest selling consumer devices in history. More than 9 million hand-held computers have been sold, the vast majority of them from one company, Palm Computing. But other companies are breaking into the market. Competition means that you have more features to choose and decisions to make if you are thinking about buying a PDA. Now, we will examine how these devices receive information, process information, and communicate with other computers and PDAs. We will also talk about the features and trends so you can make a good buying decision.


How They Work
The idea of making a small hand-held computer for storing addresses and phone numbers, taking notes and keeping track of daily appointments originated in the 1990s, although small computer organizers were available in the 1980s. One of the first PDAs that was commercially available was Apple Computer's Newton Message Pad. The Newton was too big, expensive and complicated, and its handwriting recognition program was poor. Other companies attempted to make a PDA with little success.

In 1996, the original Palm Pilot was introduced, and it was a hit with consumers. It was small and light enough to fit in a shirt pocket, ran for weeks on AAA batteries, was easy to use and could store thousands of contacts, appointments and notes. Today, you can buy Palm-like devices from major PC hardware manufacturers (Hewlett-Packard, IBM, Compaq, Sony). Though originally intended to be simple digital calendars, PDAs have evolved into machines for crunching numbers, playing games or music and downloading information from the Internet. All have one thing in common: They're designed to complement a desktop or laptop computer, not replace one.

Inside a PDA
PDAs fall into two major categories: hand-held computers and palm-sized computers. The major differences between the two are size, display and mode of data entry. Compared to palm-sized computers, hand-held computers tend to be larger and heavier. They have larger
liquid crystal displays (LCD) and use a miniature keyboard, usually in combination with touch-screen technology, for data entry. Palm-sized computers are smaller and lighter. They have smaller LCDs and rely on stylus/touch-screen technology and handwriting recognition programs for data entry.


These are the parts that can make up a PDA.

Regardless of the type of PDA, they all share the same major features:

Microprocessors


Here is a Motorola Dragonball microprocessor inside a Palm Pilot M100.

Like standard desktop and laptop computers, PDAs are powered by microprocessors. The microprocessor is the brain of the PDA and coordinates all of the PDA's functions according to programmed instructions. Unlike desk and laptop PCs, PDAs use smaller, cheaper microprocessors, such as the Motorola Dragonball, Multiprocessor without Interlocked Pipeline Stages (MIPS), or Hitachi's SH7709a. Although these microprocessors tend to be slower than their PC counterparts (16-75 MHz, compared with up to 1,000 MHz in PCs), they are adequate for the tasks that PDAs perform. The benefits of small size and price outweigh the cost of slow speeds.

Operating Systems
The operating system contains the pre-programmed instructions that tell the microprocessor what to do. The operating systems used by PDAs are not as complex as those used by PCs. They generally have fewer instructions and take up less memory. For example, the Palm operating system fits in less than 100K of memory, which is less than 1 percent the size of Windows 98 or the Mac OS. PDAs typically have one of two types of operating systems, Palm OS (3Com) or PocketPC (formerly called Windows CE, Microsoft). Palm OS takes up less memory and runs faster, and most users say it is easier to use. PocketPC easily supports color displays, graphics, miniaturized Windows packages (Word, Excel), and other devices (such as built-in MP3 players or MPEG movie players). PocketPC takes up more memory and is slower, and users say it is more complicated. As of this writing, Palm OS dominates the market, but PocketPC is challenging. Other companies are developing software for both operating systems.


Here is an inside view of a PDA. The circuit board folds away from the screen. In the middle of the single-layer circuit board is the microprocessor, and to the left and above are the memory chips.

Memory
A PDA doesn't have a hard drive. It stores basic programs (address book, calendar, memo pad and operating system) in a read-only memory (ROM) chip, which remains intact even when the machine shuts down. Your data and any programs you add later are stored in the device's RAM. This approach has several advantages over standard PCs. When you turn on the PDA, all your programs are instantly available. You don't have to wait for applications to load. When you make changes to a file, they're stored automatically, so you don't need a Save command. And when you turn the device off, the data is still safe, because the PDA continues to draw a small amount of power from the batteries.

All PDAs use solid-state memory; some use Static RAM and some use Flash memory. Some are even incorporating removable forms of memory. PDAs usually come with 2 MB minimum of memory. One megabyte of memory can store up to 4,000 addresses and 100 e-mail messages. However, many application programs take up memory space, so more advanced models usually have more memory (5 to 32 MB). Also, PocketPC takes more memory space so PDAs with this operating system usually have 16 or 32 MB. In some PDA models, the amount of memory is upgradeable.

Batteries
PDAs are powered by batteries. Some models use alkaline (AAA) batteries, while others use rechargeable batteries (lithium, nickel-cadmium or nickel-metal hydride). The battery life depends on what kind of PDA you have and what you use it for. Here are some of the things that can drain batteries:

  • Operating system -- PocketPC requires more power by virtue of its increased memory requirements
  • More memory
  • Color LCD display
  • Voice recording
  • MP3 player
Battery life can vary from two hours to two months depending upon the PDA model and its features. Most PDAs have power management systems in place to extend the battery life. Even if the batteries are so low that you can no longer turn the machine on (it will give you plenty of warning before this happens), there's usually enough power to keep the RAM refreshed. If the batteries do run completely out of juice or if you take them out of the machine, you'll have about a minute to replace them before the transistors inside the device lose their charge. At this point, most PDAs lose all their data, which makes backing up a PDA on a desktop or a laptop extremely important. PDAs also come with AC adapters to run off household electric current.

LCD Display
PDAs have some type of LCD display screen. Unlike the LCD screens for desktop or laptop computers, which are used solely as output devices, PDAs use their screens for output and input. The LCD screens of PDAs are smaller than laptop screens, but vary in size. Hand-held computers generally have larger screens than palm-sized computers. PDA displays have the following features:


Here are the parts of the PDA -- the case, the LCD screen and the circuit board. This model comes in basic black, but you can buy interchangeable covers in various colors.

Input Device
PDAs vary in how you can input data and commands. Hand-held computers typically use a miniature keyboard in combination with a touch screen. Palm-sized computers use a stylus and touch screen exclusively in combination with a handwriting recognition program. Each model also has a few buttons to bring up screens or applications. Let's take a closer look at how a stylus/touch screen works.

The tiny, four-inch screen on a palm-sized computer serves as an output and an input device. It displays information with an LCD, similar to that you'd find on a laptop. But on top of the LCD sits a touch screen that lets you launch programs by tapping on the screen with a pen-like stylus or enter your data by writing on it.

Think of the Palm's screen as a multilayer sandwich. On top is a thin plastic or glass sheet with a resistive coating on its bottom. The plastic or glass floats on a thin layer of nonconductive oil, which rests on a layer of glass coated with a similar resistive finish. Thin bars of silver ink line the horizontal and vertical edges of the glass. Direct current is applied alternately to each pair of bars, creating a voltage field between them.

When you touch the stylus to the screen, the plastic pushes down through the gel to meet the glass (called a "touchdown"). This causes a change in the voltage field, which is recorded by the touch screen's driver software. By sending current first through the vertical bars and then the horizontal ones, the touch screen obtains the X and Y coordinates of the touchdown point. The driver scans the touch screen thousands of times each second and sends this data to any application that needs it. In this way, the PDA knows when you're tapping an on-screen icon to launch a program or gliding it across the screen to enter data.

Now let's look at how the handwriting recognition works. Using a plastic stylus, you draw characters on the device's touch screen. Software inside the PDA converts the characters to letters and numbers. However, these machines don't really recognize handwriting. Instead, you must print letters and numbers one at a time. On Palm devices, the software that recognizes these letters is called Graffiti. Graffiti requires that each letter to be recorded in one uninterrupted motion, and you must use a specialized alphabet. For example, to write the letter "A," you draw an upside-down V. The letter "F" looks like an inverted L. To make punctuation marks, you tap once on the screen and draw a dot (for a period), a vertical line (for an exclamation point), and so on. To help Graffiti make more accurate guesses, you must draw letters on one part of the screen and numbers in another part.

The disadvantage of handwriting recognition software is that you have to learn a new way to write, it's slower than normal handwriting and the device's character recognition is rarely letter-perfect. On the other hand, it's surprisingly easy to learn and it works. Some PDAs let you enter data anywhere on screen and employ different recognition software (for example, Jot) that doesn't require a special alphabet (but still works better if you draw your letters a particular way).

If you can't get the hang of PDA handwriting, you can use an onscreen keyboard. It looks just like a regular keyboard, except you tap on the letters with the stylus. An accessory to some palm-sized computers is a collapsible keyboard that plugs into your PDA, which is more practical than handwriting if you use the device to send e-mail.

Eventually, most PDAs will incorporate voice recognition technology, where you speak into a built-in microphone while software converts your voice waves into data.

Input/Output Devices
Because PDAs are designed to work in tandem with your desktop or laptop, they need to work with the same information in both places. If you make an appointment on your desktop computer, you need to transfer it to your PDA; if you jot down a phone number on your PDA, you should upload it later to your PC. You also need to be able to save everything on the PDA to a desktop computer in case the batteries go dead in the PDA. So, any PDA must be able to communicate with a PC. The communication between PDA and PC is referred to as data synchronization or syncing. This is typically done through a serial or USB port on the PDA. Some PDAs have a cradle that they sit in while hooked up to the PC.

In addition to communicating through a cable, many PDAs have an infrared communications port that uses infrared (IR) light to beam information to a PC or another PDA. Some PDAs also offer wireless methods to transfer data to and from a PC/PC network through a wireless e-mail /Internet service provider like those available on new models of cell phones. Finally, some PDAs offer telephone modem accessories to transfer files to and from a PC/PC network.

Desktop/Laptop PC Software
To sync your data to or from your PDA, you install a synchronization utility (HotSync for Palm OS, ActiveSync for PocketPC) on your computer's hard drive to connect the PDA to your PC (cable, IR, wireless, modem). You'll also need to have versions of your hand-held's address book, calendar and other important applications installed on your desk or laptop, or use a personal information manager (PIM) like Lotus Organizer or Microsoft Outlook that supports syncing. The PDA assigns each record a unique ID number and notes the date it was created. (A record is one appointment, one contact, one memo, etc.) When you press a button on the PDA or its cradle, the sync software compares the record on the PDA to the one stored on your PC and accepts the most recent one. The beauty of synchronization is you always have a copy of your data, which can be a lifesaver if your PDA is broken or stolen or simply runs out of power.

Future Trends in PDAs
The PDA market is changing quickly, especially as companies such as 3Com (makers of PalmPilot) and Microsoft vie for dominance. Here are some of the trends:

  • Add-ons and multifunctional devices. PDAs and Global Positioning System (GPS) receivers will be combined into one handheld device. Some PDAs will be able to capture and store images, as a digital camera does. You can already see this trend in the add-on devices for the Handspring Visor.
  • Built-in audio. PDAs will come to you ready to play audio files.
  • Wireless connectivity. Manufacturers are interested in using the Bluetooth short range radio system to connect PDAs to other devices. Hewlett-Packard is developing software that could wirelessly connect a PDA to a printer.
  • Both smaller (wristwatch size) and bigger (with more add-ons).
  • Internet connectivity as in the Palm VII.
New PDAs will communicate more with the Internet wirelessly. Instead of downloading entire Web pages to your PDA, Palm devices use a process called Web clipping to slice out bits of text information and send the text through the airwaves to your PDA. For example, say that you want to get a stock quote from an online broker such as E-Trade. You tap the E-Trade icon, fill out a form on your PDA listing the ticker symbol and tap the Send button. Your text query is sent via a data packet-paging network to an Internet server. Software on the servers searches the E-Trade site, then transmits the answer back to your PDA. News headlines, phone numbers, e-mail and other information can be transmitted in the same way. Eventually, PDAs will merge with cell phones and use a cellular network to communicate via voice as well as text. It is also likely that PDAs will become faster and have more memory as computer technology advances. Intel has announced a new microprocessor called Xscale that can run at 1 GHz and draw power from a single AA battery.


What They Can Do

Psion Revo Plus
PDAs were originally designed as organizers. They could store addresses and phone numbers, keep track of appointments, and carry lists and memos. PDAs still do those things, but they are now more versatile. They can retrieve or send e-mail or download other information from the Internet. They can play music, movies and video games. If you wonder whether you could use a PDA and whether it would be worth the money (the average cost is about $400), you should take a look at the basic tasks that can be done with a PDA, but you also might find other uses that you never even thought of.

Here are things that PDAs can do:

Who Uses PDAs?
PDAs can help technicians making service calls, sales representatives calling on clients or parents keeping up with children's schedules of doctor's appointments or after-school activities. In addition to the basic functions, there are thousands of specialty programs available for PDAs, including maps, sports statistics software, decision-making software, etc. Here are just a few examples of specialty uses for PDAs. These give you clues to the PDA's versatility.

  • Health Professionals
    Many health professionals (physicians, nurses, pharmacists) need to keep track of patient information (medications, treatments). Often, there are not enough computer terminals in the clinic or even at the bedside. In addition, many health professionals need access to information about pharmaceuticals (pharmacopeias, Physician's Desk Reference, Clinician's Pocket Reference), emergency room procedures and other medical or nursing procedures.

    Instead of carrying manuals with procedures or references or index cards with patient information in their pockets, doctors and nurses can put the information on a PDA. They can note patient information at the bedside in the PDA for later upload into a PC. They can download drug and procedural reference materials into a PDA for consulting at bedside. They can have programmed drug dosage calculators in their PDAs.

  • Amateur Astronomers
    The equipment that an amateur astronomer takes out in the field when observing is sometimes daunting. Not only does it include the telescope, telescope mount, eyepieces and cold weather gear, but also includes star charts, field guides and notebooks. Some astronomers have to carry a laptop to drive their computer-guided telescopes. So many of these loose items get scattered across an observer's table and are easily misplaced in the dark. If an amateur astronomer had a PDA, he or she could download a planetarium program into the PDA, which could serve as star chart and field guide. Then, they could take observation notes on the PDA and later upload them into a PC. The PDA could replace a laptop and drive the computer-guided telescope to the desired celestial coordinates. All of these functions could be done with one PDA instead of several other items.

  • Truck Drivers
    Truck drivers on the road must frequently communicate with their companies and their homes. They consult e-mail and keep track of expenses, shipping records, maps and schedules. Many drivers use laptop computers in their trucks to take care of these tasks. However, laptops have relatively short battery life and are bulky. PDA models and software available now can do many of these functions, from personal information management to mapping and wireless e-mail.


Features
Personal digital assistants (PDAs) are one of the fastest selling consumer devices in history. That popularity means that there are many models to choose from. You should first ask yourself "What do I need my PDA for?" and "How much can I afford to spend on a PDA?" The answers to these questions will help you find the right model. Here is a list of features that should be considered:

Size
Do you want a PDA that you can carry in your briefcase or in your pocket? PDAs come in hand-held or palm-sized models. The hand-held computers tend to be larger than the palm-sized. Most, but not all, palm-sized PDAs can fit into a shirt pocket. Also, PDAs vary in their weight from 4 to 8 ounces (113 to 227 grams).

Type of Data Entry
Which type of data entry do you prefer? Most hand-held PDAs use a miniature keyboard for data entry. Often the keyboards are too small for easy or comfortable typing. In contrast, palm-sized PDAs use a stylus/touch-screen technology in combination with hand-writing recognition software. This involves learning some shorthand alphabet, such as Palm's Graffiti, which can take some time to master fully.

Operating System
This is one of the most important decisions to make! It is the PDA equivalent to "Should I buy an Apple Macintosh or IBM PC/PC clone?" The operating system used by PDAs are one of two types, Palm OS (3Com) or PocketPC (formerly called Windows CE, Microsoft). Palm OS takes up less memory, runs faster, and is easier to use. PocketPC easily supports color displays, graphics, standard Windows packages (Word, Excel), and other devices (e.g., built-in MP3 players, MPEG movie players); however, PocketPC takes up more memory, is slower, and more complicated to use. However, if it is important to be able to exchange files with Windows packages, then PocketPC might be a better choice. As of this writing, Palm OS dominates the market because its operating system is specifically tailored to the basic uses of a PDA. However, PocketPC is challenging Palm OS, and third-party software developers exist for both operating systems.

Display
All PDAs have LCD displays. PDA displays have the following features:

Memory
All PDAs use solid-state memory, usually flash memory; some are even incorporating removable forms of memory. PDAs usually come with 2 MB minimum of memory. One megabyte of memory can store up to 4000 addresses and 100 e-mail messages. However, many application programs take up memory space, so higher models of PDAs usually have more memory (5 to 32 MB). Also, PocketPC takes more memory space, so PDAs with this operating system usually have 16 or 32 MB. In some PDA models, the amount of memory is upgradeable.

Power Supply
PDAs are powered by batteries. Some models use alkaline (AAA) batteries, while others use rechargeable batteries (lithium, nickel-cadmium, nickel-metal hydride). The battery life depends upon the following:

  • operating system - PocketPC requires more power by virtue of its increased memory requirements
  • amount of memory
  • color LCD displays
  • special features (voice recording, MP3 player, wireless connections)
Therefore, battery life can vary from two hours to two month,s depending upon the PDA model and its features. Most PDAs have power management systems in place to extend the battery life. Even if the batteries are so low you can no longer turn the machine back on (it will give you plenty of warning before this happens), there's usually enough power to keep the RAM refreshed. If the batteries do run completely out of juice, or you take them out of the machine, you'll have about a minute to replace them before the transistors inside the device lose their charge. PDAs also come with AC adapters to run off household electric current. In some models, an AC adapter is not included, but rather is sold separately.

Communication
Because PDAs are designed to work in tandem with your desktop or laptop, they need to work with the same information in both places. If you make an appointment on your PC, you need to transfer it to your PDA; if you jot down a phone number on your PDA you'll want to upload it later to your PC. So, any PDA must be able to communicate with a PC. The communication between PDA and PC is referred to as "data synchronization" or "syncing." This is typically done through a serial or USB port on the PDA. Some PDAs have a "cradle" that they sit in while hooked up to the PC. This feature is typically standard on all PDAs with the only choice being serial or USB port.

In addition to communicating through a cable, many PDAs have an infra-red communications port that uses infra-red (IR) light to beam information to another PDA or PC (the PC must have a receiving IR sensor!). Some PDAs also offer wireless methods to transfer data to and from a PC/PC network through a wireless e-mail Internet service provider like those available on new models of cell phones. Finally, some PDAs offer telephone modem accessories to transfer files to and from a PC/PC network. Check the model to see if any of these features are standard or require extra devices.

Special Features
Some PDAs have special features such as:

  • send or receive e-mail - available on some models. This feature will likely become standard on PDAs in the future.
  • do word processing - currently available on some hand-held models and PocketPC PDAs
  • play MP3 music files - currently limited to PocketPC palm-sized PDAs
  • play MPEG movie files - currently limited to PocketPC palm-sized PDAs
  • access Internet information (news, entertainment, stock quotes) - available on some models only
  • play video games - video game software is currently available for many models

Software
All PDAs come with some kind of personal information management (PIM) software for the following tasks:

  • store contact information (names, addresses, phone numbers, e-mail addresses)
  • make task or to-do lists
  • take notes
  • write memos
  • keep track of appointments (date book, calendar)
  • remind you of appointments (clock, alarm functions)
  • plan projects
  • do calculations
  • keep track of expenses
However, not all of these functions are included in every package, so check this before you buy. Also, make sure that your PC has similar software so that you can easily exchange information between your PDA and PC. Sometimes, PC PIM software is included with the PDA software.

In addition to these functions, consider the following software needs:

  • ability to exchange and work with Windows packages - currently available only on PocketPC PDAs
  • data synchronization software - this is usually standard, but may be extra in some models
  • specialty - thousands of programs are available for PDAs with both operating systems. These include maps, medical software, decision-making software, astronomy programs, etc. Many are available as freeware or shareware.


When You Shop
We've created a feature comparison chart for you to use as you research various PDAs. Take it to the store with you and fill in the blanks for each model you are interested in. You may also want to keep an additional copy near your desk as you research PDAs on the Internet.

The feature comparison chart is available to you as a PDF. You will need the free Adobe Acrobat Reader to view it.

Popular PDAs
Here are 10 of the best-selling PDA models listed for comparison.


Palm m100 Handheld

Palm V Handheld

Palm Vx Handheld

Handspring Visor Deluxe (Graphite)

Palm IIIxe Handheld

Compaq Aero 1550 Pocket PC

Hewlett Packard Jornada 548 Color Pocket PC

Palm VIIx Wireless Handheld


Look Out!
When purchasing a PDA, there are several things you should keep in mind to avoid buying a PDA that won't meet your needs. Here are some of the most common things to think about:

Screen
Check out the size of the screen. Is it easy to write on or does it feel cramped? Can you see the screen clearly under various lighting conditions?

Operating systems
Is it easy to open and close applications? Can you have multiple applications running at the same time?

Data synchronization
Will your PDA synchronize with your PC and favorite personal information management software? For example, some models do not sync with Microsoft Outlook unless you buy an add-on.

Memory
Is there sufficient memory for your use? If you download application programs, some take up large amounts of memory? Is the memory upgradeable?

Expandability
Does your PDA have expansion slots or options for peripheral devices? Consider what types of communications ports that you require. Will you need more memory?

Software
Make sure that the included software suits your needs!


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