The two basic types of PDAs are the palmtop computer and the pen-based PDA. A palmtop computer is styled similarly to a laptop computer, only it is smaller. A palmtop has a landscape-mode screen and a full QWERTY keyboard. A pen-based PDA is typically a portrait-mode device with a touch-sensitive screen and a stylus, but no keyboard. Pen-based PDAs use various types of handwriting recognition to translate the user's writing to text, and usually offer a small, on-screen 'keyboard' to allow the user to 'type' text on the screen. To confuse matters more, some palmtop machines also have touch-sensitive screens and use a stylus.
Various companies have produced PDAs of various types. Psion, a UK company, has been building palmtop computers for many years. Apple Computer produced the Newton, which was the predecessor of the current range of pen-based PDAs (but is itself long out of production). When Apple killed the Newton program, the Newton design team reportedly went on to design what has become the Palm platform (and the similarities between the two are quite striking). A latecomer in the PDA game has been Microsoft, with their Windows CE operating system (now renamed PocketPC, due to the negative image attained by CE), running on machines produced by a variety of companies, and in both palmtop and pen-based form factors.
Right off the bat, the author must confess to being much more fond of palmtop computers with real keyboards than pen-based PDAs. This page is being written on a Psion Series 3c (an older model palmtop) in the field. Serious data entry of this sort is simply not practical with a stylus and touch screen. While separate keyboards are available for many pen-based PDAs, they are not particularly practical. They are much larger than palmtop keyboards, resulting in rather ungainly contraptions when fitted to their mating PDAs. One may as well use a full-size notebook computer at that rate. Some of the add-on PDA keyboards fold for storage as well, with the result of very little structural integrity due to the need for multiple hinges and the flexing of multiple ribbon cables.
Palmtops also typically offer larger screen resolutions than do pen-based units. This older Psion has a 480x160 LCD, which is the equivalent of three Palm screens (only 160x160) side-by-side. Unlike a Palm device, a typical palmtop can display such things as email messages in their native form, in the standard width of 80 columns. The landscape-mode display of a palmtop is also more natural for viewing (hence the great width of movie theater screens, and the recent trend toward widescreen television).
The author is fond of compact, stable, and efficient operating systems, as well as elegant hardware architecture designs.
While some of the hardware of Windows CE devices is impressive in specifications, it is not particularly efficient. Said operating system is not at all compact, stable, or efficient. For this reason (and others), CE devices will never be regarded as serious contenders in the PDA field.
Palm devices do use a more efficient operating system and architecture than do CE devices, but they have too many other limitations to be considered seriously. The Palm OS apparently does not even have a real filesystem.
Psion, with their older EPOC16 and current EPOC32 operating systems, running on their own highly efficient hardware, have created the world's best palmtop computers. EPOC32 is also very commonly used as the OS embedded within many mobile telephones and other systems.
Power sources vary among different PDAs. Some use standard alkaline cells, while others use various types of rechargeable battery packs (including all of the PDAs with color displays). As far as the author is concerned, a color display on a handheld machine is nothing more than a gimmick, as the power consumption alone is far too high to yield a practical platform. More efficient machines can operate for tens of hours from standard alkaline cells (such as the author's Psion, which typically runs for 20-40 hours from two AA cells). The ridiculous system resources required to run Windows CE also result in excessive power consumption. All of these factors contribute to making a color pen-based CE device the worst possible PDA. Even though the Palm platform (with the exception of color devices) is efficient enough not to require rechargeable cells, many Palm devices use them anyway. Some may regard this as a feature, but to the author, it is a liability. All rechargeable cells have a finite lifetime, and if they are buried deep within the machine, replacement can be quite tedious. If one is using a PDA in the field and the rechargeable cells run down, the user must find a power source (and have the required charger along), or be out of luck. In contrast, it is a simple matter to carry a few spare alkaline cells with the machine.
Another power issue is that of backup batteries. Many PDAs use some sort of battery (often a lithium coin cell) to retain their memory contents when the main batteries die, and/or while changing batteries. Apparently, the Palm platform does not use any sort of backup battery. This means that, if the main batteries die, the machine loses all of the information stored in its memory. If caught in the field with dead rechargeable batteries for too long, one will lose everything. That is simply inexcusable in the mind of the author.
Last updated: 7 February 2001
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