It's amazing, when you think about it, how many personal computer users there are who still don't have a SideKick.

I don't mean a sidekick of the Tonto/Kemosabi variety. I mean an accessory or "desktop" software program like the famous SideKick, the programming innovation that created this indispensable new category of software.

Indispensable? Definitely. You wouldn't try to use your computer without a monitor or keyboard or disk drive. As I see it, a SideKick program is equally essential. And yet I talk to PC users all the time who still don't have one.

The function of SideKick and its many clones is to automate and organize the cluttered set of tools on a normal desktop: the appointment calendar, the notepad, the alarm clock, the Rolodex, the pocket calculator, etc.

The great genius of these programs is that they are "memory resident." That means the desktop program loads automatically into memory when you first turn on your computer, and then it is instantly available whenever you need it.

There's no need to find a disk and load a program; you just hit a key and a window opens on the screen -- right on top of the program you're using -- with your electronic calendar, message pad or whatever. When you're finished with it, you hit the Escape key and the window disappears, returning you to whatever program you were originally working on.

When I first discovered SideKick a year ago, I was intrigued with the idea but a little skeptical. My trusty old desk calendar, message pad and pencil had worked fine for years. What was the point of putting them in the computer?

After months of satisfied use, I know the difference -- and I'd never go back.

For one thing, the computerized desktop tools are always there. Everybody knows that the pencils of the world have conspired to disappear just when you need one to write down a crucial order or phone number. But that Notepad function in SideKick will always pop up the instant you press a key.

For another, computerized messages, phone lists, etc. don't get lost. Is there anyone who hasn't had the experience of scrawling down the address of an important meeting on a scrap of paper -- and then losing the scrap? With desktop programs, that address would have been filed automatically on a disk as soon as you finished typing it in.

The computerized tools are faster than the pencil-and-paper versions -- particularly if you spend much of your day at the computer keyboard anyway. I thought that nobody would invent a faster telephone directory than the ingeniously simple Rolodex. But the phone list in SideKick works faster -- and can dial the number automatically once you find it.

Finally, as I noted last year, the desktop programs eliminate that ignominious feeling that comes when you're using your $5,000 computer but have to dig through a drawer for a $9.95 calculator to add a column of numbers.

You could, of course, file away whatever you were doing on the computer, load up a spreadsheet program, and add the figures that way -- but in the time this would take, you could get the answer on your fingers.

With SideKick and its copycats, the calculator is always ready. And once you get the result of your calculations, you can automatically move it to a letter, an invoice or whatever else you are working on at the time.

Some of the desktop programs have additional goodies. A common feature is an alarm clock that will beep at you and flash a message on the screen at a given time. Some will automatically print out the next day's appointments when you leave the office at night. Some let you jump back to DOS or to another application program without the need to exit and store the data base or spreadsheet you are currently working with. Some include programmer's tools like a listing of ASCII codes and instant decimal-hexidecimal number conversions.

Thanks to the good example set by Borland International, the makers of SideKick, most desktop programs are relatively cheap -- $50 or so via mail order -- and not copy-protected. At the moment, this category of software represents the best bargain in the personal computer marketplace.

So why doesn't everybody have a SideKick? Maybe people have been confused by the torrent of new desktop programs flooding the market.

To help out, I'm currently test-driving a sample of the available choices -- including a brand-new program that brings the SideKick concept to the world of CP/M computers. In a couple of weeks, I'll report on my findings. Watch this space!