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. In this article, 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.
PDA Basics
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.
The parts that can make
up 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.
PDA Parts
Regardless of the type of PDA, they all share
the same major features:
Microprocessors
Motorola Dragonball microprocessor
in a Palm M100
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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.
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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:
- LCD, enhanced LCD, or color super-twist nematic
(CSTN) types (See How
LCDs Work for details.)
- pixel resolutions (160 x 160, 240 x 320)
- black-and-white (16 grayscale) or color (65,536
colors)
- passive
or active matrix -- active matrix displays
have sharper images and are easier to read
- reflective
or backlit -- backlit screens are good for
reading in low light
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.
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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.
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.
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:
- 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 resolution - PDAs have various
pixel resolutions (160x160, 240x320). 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
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:
- E-mail
- Word processing
- MP3 music files
- MPEG movie files
- Wireless Internet
- Video games
- GPS receiver
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. Additional specialty software
may also be available, including maps, video games,
and photo editing software.
Manufacturers
Popular PDAs
Here are some of the best-selling PDA models,
listed for comparison.
