I'm pretty good with computers; I know this port from that port and where to bang the case when the disk drive sticks. But an unfamiliar computer is like a rental car, and the Psion Series 3a pocket computer ($545; 800-547-7466), an anniversary present from my wife, is like a tiny, delicate-looking foreign rental car. Can I safely bang on the case to free up the disks? Are there disks? How do I connect a printer? Why do I want this thing?

Why do I want this thing? -- that question keeps coming up. But if my wife, a research genius, selected a Psion, it has to be the best of its kind, whatever kind it is.

For starters, it's a word processor that's compatible with Microsoft Word, which I use in the office. The small keyboard has all the keys I need; it's fine for memos and E-mail but too small for typing longer documents. It lacks a pointing device, and the keyboard combinations for moving documents take time to master.

But first things first: Read the manual. I always read the manual. Doesn't everyone? The Psion has a good manual. More than 250 pages -- larger than the computer but not nearly as sturdy. Psion or someone else should design a case for the manual. My manual is pretty beaten up from having been on the road with me. But it is well done and easy to read. Protect the manual!

The Psion uses solid-state disk drives, SSDs. It comes with one SSD installed and room for two removable drives, which are available in sizes of up to 4 megabytes. They are expensive and compatible only with the Psion; I don't think that I will ever buy one. I wish the Psion had a larger internal SSD and an external 3.5-inch floppy so I could save files to the disks that are available everywhere, already formatted, for 89¢. I can also back up files to another computer -- a Mac or a PC -- connected directly to a serial or a parallel port.

I do a great deal of E-mail and fax correspondence, so the computer's $300 3FAX/modem is an attractive option. It turns the palmtop into a portable fax machine, and allows me to connect to my E-mail system and on-line services. Now, if Psion engineers were to take my advice on disk drives, they would eliminate SSD ports and integrate the modem into the body of the Psion.

The Psion dials the phone for me directly from address files, either over the modem or by playing tones while I hold the machine next to a telephone headset. It can also be used with cellular phones. (Maybe the engineers could replace the second SSD port with a cellular phone. That would make it a truly amazing machine.) So I have a tiny computer, a fax, a modem, and a word processor all in the same amount of space as my address book and my calendar book combined.

In fact, the Psion also has an agenda program that can replace my calendar and a database system that can replace my address book. I will part with my paper address book and calendar when I get all the information entered -- a major rite of passage for me.

OK: a tiny computer, a fax, a modem, a word processor, an address book, and a calendar, all taking about the same space as my calculator. What else? The Psion is also a complete scientific calculator. And a spreadsheet. It uses the same file formats as Lotus 1-2-3. So I can read the files into any other spreadsheet capable of accepting 1-2-3 WK1 files. It allows me to password-protect files and to lock the entire machine. It has dual batteries and all sorts of safeguards against loss of power.

The Psion has the makings of a cult icon. If you need to do DOS, Windows, or Mac applications, you'll need another machine. And if I were buying a small computer I would buy a notebook or a subnotebook with an integrated fax-modem and floppy and a more practical keyboard. But with a few engineering changes . . .

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Sandy Friedman is the founder and CEO of Counterpoint Publishing Inc., in Cambridge, Mass.