Unlike other handwriting-recognition devices, tablet PCs normally leave your scribbles as "ink" on the screen. This divorce of ink from text fatally compromises the tablet PC's usefulness.

First, if your writing is unreadable on paper, it will look even worse after being digitized as ink.

Second, ink is an inefficient, incompatible way to store words. An 11-page handwritten document measured 422 kilobytes, a lot to download in e-mail or fit on a floppy disk. Ink files can't be edited on anything but a tablet PC, and e-mails written in ink may be unreadable in many mail programs, especially those on a cell phone or handheld organizer.

The tablet PC software offers only limited, clumsy ways to transform ink into text. In Windows Journal, the core handwriting-input program, you can select up to a page's worth of ink, then navigate to the Actions menu and select "Convert handwriting to text" (a tricky maneuver with a stylus); the software will offer its interpretation as well as alternative transcriptions of any words it's unsure of.

With most other applications, you need to invoke a foreground window called the Tablet PC Input Panel, which accepts your handwriting, converts it in batches and pours the results into the current document.

If you leave your ink as is, the tablet PC will still do some transcription in the background, which lets you search inexactly through an ink document: It correctly found one instance of "compact" but thought it had located three more in the words "control," "comfortable" and "computing."

Take care to write slowly and precisely in cursive or print and the tablet PC may perform quite well. But if you rush, things go downhill in a hurry. (The tablet PC just interpreted that phrase as "Things go downhill or, a henry!") Its suggestions for alternative spellings can resemble the rantings of an increasingly deranged poet, such as these interpretations of "Christine": "Christie, Caroline, Caustic, Carotene, Carthorse, Christ-ire."

At no time can you see a tablet PC's transcription in real time, letter by letter, which blocks you from learning what parts of your writing confuse the software. It breaks the feedback loop that lets users of other pen-input systems -- Palm handhelds' Graffiti, Apple's Ink for Mac OS X and Microsoft's Pocket PC -- improve their accuracy.

The tablet PC software, in turn, isn't programmed to learn from your use of it.

This setup has been puzzling me all week. Half a decade ago, Apple's Newton MessagePad 2000 transcribed my handwriting with impressive accuracy while running on a far weaker processor. Can't Microsoft do better today?