What's the most widely used program for personal computers? It's the one shared by every machine: its operating system.

For most people that means MS-DOS. It starts your computer in the morning, checks the memory chips to see that they're working right and sends data to the printer when you're ready for hard copy. It lets you know what's on your disks and paints text and images on the display screen.

But there are a lot of things DOS doesn't do. It doesn't set up your hard disk to operate at its highest speed. It doesn't preserve complicated commands as "macros" that you can run again with a few keystrokes. It doesn't protect your machine against virus infections and it can't keep your files secret by encoding them. Worst of all, if you accidentally delete a file, DOS can't easily "undelete" it.

DOS is also taciturn when it comes to telling you what's inside your computer, from how much expanded memory you have to how fast your co-processor runs to what your disk "interleave" factor is and what it should be.

To fill all those holes, there's a big business in utilities these days. The Norton Utilities and PC Tools are the two biggest names.

Now there's another big name in the utility game: Ashton-Tate Corp., the company that brought you dBASE, offers a utility called Control Room ($129, (213) 329-8000).

Control Room has two parts: one that inspects your IBM Personal Computer or compatible and tells you what's inside and another that can tune your machine to operate at its most efficient pace.

The inspector in Control Room will test every part of your system except removable hard disks, such as Bernoulli drives. And for most parts, it will offer some customization options.

Control Room will tell you what kind of central processor chip your system has, how fast it runs and how many "wait states" your memory chips require. (Wait states are short periods when your central processor "waits" for the slower memory chips to catch up with it electronically. They help you gauge the true speed at which the computer works. The more wait states, the slower the machine). Control Room will do the same job for any math co-processor chip you have. It will find and list the serial and parallel ports in the system, the display adapter type, the version of DOS you're using, what sort of keyboard you have and the size, speed and interleave of the hard disks on the system.

For the keyboard, Control Room can increase the "type ahead" buffer (so you can type as fast as you want and not lose characters), change the volume of the beep sound and set the "repeat" speed of keys (how quickly a key shoots new characters onto the screen if you keep pressing it). It also offers a macro feature for recording and reusing any series of commands. (For example, if you find yourself typing "National Aeronautics and Space Administration" over and over, you could make a macro of the phrase and thereafter zip it out just by pressing Alt-N.)

For your hard disk, Control Room will tell you the disk's access time, controller type, physical layout and interleave (a technical factor that affects speed). It can "safe park" the disk (so the "head" that reads information won't bounce and damage the disk) and has a caching utility that can keep the most used information from the disk in RAM chips for even greater speed.

Control Room can test your computer's memory, tell you how much conventional, extended and expanded memory you have and list the programs in memory.

In its own simple editing window, Control Room lets you see and change your AUTOEXEC.BAT and CONFIG.SYS files. That's a great help if you're a tech type who wants to configure your system. It's even more of a boon to someone who doesn't know about those files but needs to tell a tech support person what's in them.

Like Norton Utilities or PC Tools, Control Room can "undelete" a file, though it isn't as flexible as those programs in finding and recovering files. It can hide a file in code and then later decode the file. And it can absolutely erase everything on a floppy, not leaving scraps of files behind as the DOS delete command does. Control Room will also inspect important files each time you start your PC to see if they have mysteriously changed in size. That could indicate a virus infection. Control Room can't disinfect your system, but it can provide some warning of trouble.

Control Room wraps all this analysis into a single "Comprehensive Expert Opinion" that's like having an unbiased and fairly lucid computer nerd at your side.

The opinion will look at the details of your system and tell you how it matches up in the world of PCs. Is your processor chip fast enough? Do you need a math co-processor? Do you have and should you care about expanded memory? What about your hard disk speeds? (My main drive is an old 21-megabyte hard disk, and Control Room was blunt: "This drive has a very slow average access time. For routine character-based word-processing and low-demand office chores, this drive may prove satisfactory.")

The only problem I bumped into was with the macros -- they didn't work on my AT clone. Whenever I turned the macros on, the keyboard turned off. The technical support staff at Ashton-Tate thinks it must be some conflict between Control Room and my brand of AT. They were surprised, apologized and promised to find a solution. For now, I can live without the macros.

Control Room is easy to install and has a great little manual (crucial if I'm going to read the thing). But I don't think you will need to read it because the on-line help covers the ground just fine. With the menus and on-line help, you can run Control Room with just the return, escape and arrow keys (or a mouse).

I'm sold on Control Room. I think DOS should provide most of these facilities (is Microsoft listening?), but as long as it doesn't, I'm willing to pay extra to get them. At $129, the price is a bit steep (that's more than I paid for DOS), but maybe by mail order you'll see Control Room for $50 or so. At that price, it's something every PC should have.

Phillip Robinson is an author of books and articles about computers and an editor for Virtual Information of Sausalito, Calif.