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 - hand-held vs. palm-sized
  • Type of data entry - keyboard vs. stylus/touch-screen
  • Operating system - PalmOS vs. PocketPC (formerly Windows CE)
  • Display
  • Memory
  • Power supply - disposable vs. rechargeable batteries, AC adapter
  • Communication
    • cable - serial vs. USB port
    • infrared (IR)
    • wireless
    • telephone modem
  • Special Features
    • e-mail
    • MP3 player
    • MPEG player
  • Software
    • personal information management (PIM)
    • spreadsheet, word processing, calculator
    • voice recognition
    • data synchronization
    • specialty
    • availability
  • Price - $150 to $1,000

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.

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

  • color vs. monochrome - Most PDAs are black-white (16 gray scales), but some have colors (65,536). PDAs with color screens need more memory and tend to be more expensive.
  • pixel resolutions - PDAs have various pixel resolutions (160 x 160, 240 x 320). The higher the resolution, the clearer the display.
  • passive or active matrix - active matrix displays have sharper images and are easier to read, but tend to be more expensive
  • reflective or backlit - backlit screens are good for low level room lighting conditions
  • size - Hand-held PDAs tend to have larger screens. Most palm-sized PDAs have four-inch (10 cm) square screens.
  • writing area - Some PDAs only allow you to write in special areas of the screen, while others allow you to write anywhere
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.

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

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.