In theory, it seemed like a great idea. Why not let the microcomputer take over the dreary daily routine: keeping track of things to do, places to go, people to see. Freed of these mundane, quotidian chores, the executive could concentrate on important tasks -- like running the business.

Thus, in 1979 was born Time Manager, a personal scheduling and appointment software package that has spawned at least 25 imitators. Ranging in price from less than $55 to more than $990 (for The Scheduler, from Micro Information Systems Inc. of Montgomeryville, Pa., a program dedicated to untangling the complicated lives of attorneys and accountants), the majority do many of the same calendar-juggling tasks -- some, however, better than others. A few of the programs will diligently search for an open time slot; others will remind you that an important meeting is coming up. Many produce expense reports; some will coordinate a number of different schedules.

For the most part, though, these programs have failed to fire the managerial imagination. "Let's just say [Time Manager] wasn't the biggest hit in the world," says a spokeswoman for Microsoft Corp., a Bellevue, Wash.-based software publishing house that recently dropped the version of the program it had been distributing for Apple computers.

Why have executives been reluctant to dump their Day-at-a-Glance paper calendars in favor of electronic schedulers? "A lot of them still seem to prefer the human element," says Andy Johnson, manager of Your Business Software Inc., a Dallas retail outlet that has sold only two or three of these programs in six months. "They have a secretary who tugs on their sleeve and says, 'Mr. Jones, you have an important board meeting in the morning.' Those who do buy the programs often find that they don't perform the kinds of jobs they thought they would or don't do enough to warrant the effort involved in updating them."

Until recently, however, one of the greatest liabilities of time management programs was the fact that the computer had to be dedicated entirely to their use in order for them to work most effectively. "If I'm doing word processing or spreadsheet analysis and someone gives me a call and says, 'Hey, can we get together for lunch next Thursday?' says Paul Schuman, software product manager for Businessland Inc., a 15-store San Jose, Calif.-based computer retail chain, "I've got to save the document I've been working on, take out the disk for my time manager, stick it in my computer, boot up the system, and about three minutes later I can see whether I have any time free next Thursday."

The alternative, of course, is to use the computer strictly as an electronic scheduler. And, points out Marty Winston, president of Winston & Winston Inc., a nine-employee Fort Worth marketing communications consulting company, "the last thing a person needs is a $5,000 calendar."

In the past few months, however, software developers have come up with a solution: programs that allow users to switch easily among many different software packages that are stored in the machine's memory. Now you can forge ahead with Lotus 1-2-3, for example, while keeping a time management program running in the background. Punching one key lets you jump quickly from one package to the other without interrupting work in progress.

Despite their limitations, not everyone finds time management programs unappealing. George Hayles, former editor and vice-president of PC Info Inc., a Marietta, Ga., start-up that publishes a biweekly newsletter for business users of the IBM Personal Computer, uses Shoebox (Techland Systems Inc, New York City; $125), a scheduling program that he found helpful from day one. "I'm the kind of person that doesn't like to leave loose ends," he says, "and this has a way of reminding me of all the loose ends that need to be tied up."

Shoebox, which purports to "tidy your life," lets users keep appointments, expense reports, and a daily reminder list separately -- the feature Hayles finds most valuable. When he arrives at the office each morning and powers up the computer, "the first thing I do is look at that list of things to do and see what I scheduled for myself today."

If Hayles knows he will need to do some task three weeks down the road, he simply enters the job and the date it should be done. When the critical day arrives, that task pops up on the day's reminder list. And if he doesn't get the job done on time, it, and any other unfinished business, crops up the following day with an asterisk alongside it.

But it is the program's capacity to handle recurring events that receives highest marks from Hayles. Given his line of work, he places a high priority on attending his IBM PC user group meetings. Although the group meets regularly -- the third Wednesday of every month for the business subgroup and every second Wednesday for a general gathering -- Hayles would just as regularly forget.

Before getting Shoebox, he says, "I thought about [the meeting] at 7:20 on a Wednesday night, and it starts at 7:30 "

Now he just tells the program when his meetings take place, and it slots in the appropriate Wednesdays. "I don't care what combination you come up with -- this meeting is going to [occur] every nth day on a leap year -- it'll remind you," he says. As an added precaution, he tells Shoebox to start nudging him about his commitment three days in advance. "When I fire up on Monday morning," he says, "it reminds me that those meetings are coming up during the week."

Since Hayles spends most of his time editing and writing, he asked Shoebox's authors whether it was possible to keep the program loaded while working with WordStar. They suggested Memory/Shift (North American Business Systems Inc., St. Louis; $99), a program that lets users switch among as many as nine packages. (Techland Systems now sells Memory/Shift as an option. Together, the two programs go for $195.)

But Hayles is not entirely satisfied with Memory/Shift, which he bought. When he is using it, he has difficulty operating other so-called utilities, such as a print-spooling program that lets him run the printer while working on another task. And if he partitions his PC's memory, he says, he can't use internal RAM as an electronic disk drive -- a trick that allows users to retrieve data much faster than they can by relying on an external disk for storage Still, Hayles appreciates the additional flexibility Memory/Shift allows him, and usually keeps WordStar in the forefront, with Shoebox just a keystroke away in the background.

While Hayles finds Shoebox beneficial for a limited, albeit important, function -- jogging his less-than-perfect memory -- Jeri Laizure, owner and president of Laizure/Woodward & Wise, an advertising agency in Charlotte, N.C., considers The Desk Organizer (Conceptual Instruments Co., Philadelphia; $250) critical to nearly every aspect of her working day Laizure's unusual devotion to the contents of a floppy disk had its origins in great expectations. Unlike many other executives, she didn't think the primary value of a microcomputer lay in its wordprocessing or spreadsheet capabilities. Instead she hoped the IBM PC she bought last January would help her better organize her day-to-day activities.

"I was looking at bits and scraps of different colored [and] sized pieces of paper with things on them that had no meaning, no logic, no order. And I'm a very organized person," she says. Besides, she adds, "ever since I got the computer my first question was, What do I use this thing for really, moment to moment, in my business life? You're not writing a novel all day. You're not doing VisiCalc all day. What I do is try to keep up with my time and my information." On the alert for software that would serve this end, she snapped up Time Manager after reading a few reviews of the program.

Laizure was soon disillusioned. "First of all," she says, "you tie up the computer totally." Since the program uses a modified form of MS-DOS, the IBM PC's operating system, it doesn't work with Memory/Shift, which functions only with packages employing standard MS-DOS. And there was no other similar software on the market to do the job. While Time Manager did track appointments and expenses and provide space for some note-taking, it was, Laizure found, "extremely limited." All it is, she says, is a "to-do list, and I found that I didn't need to be looking at a screen all day telling me I had a 2:00 appointment."

Poking around further in the computer magazines, she came across an interview with Conceptual Instruments Co. president Fred Collopy, and decided that his ideas of "desk management" matched her own. Conceptual Instruments's program, The Desk Organizer, does just about everything except play "For He's A Jolly Good Fellow" at the end of a rough day. Organized around "indexes," a note-taking system that lets you file jottings in up to 21 categories of your choosing, it will alert you with a chime when you have an appointment, look up telephone numbers, place calls, calculate, stamp items with the correct time and date, control a printer and other peripherals, and inform you, via a gas-gauge-like symbol, how much space remains on your disk.

It also has its own program-switching capacity, called Meta. "That's very important to me because I write," says Laizure. Now she loads EasyWriter II and The Desk Organizer and goes back and forth between the two. "That takes care of my entire day," she says.

The program's note-taking format is more like a "miniature file cabinet" than a Rolodex, says Laizure. She maintains a quote index with bids from all her suppliers, a schedule index with appointments and her to-do list, a company/person file, and an index, which contains pertinent information, as well as names, addresses, and phone numbers, for each of her clients. She keeps salutations and endings in a letter and memo index, which she uses instead of EasyWriter for short notes, and has a copy-writing file for ad copy. And her media index gives her instant access to rates for local radio, television, and newspapers. "I've got everything on here," she says. "It's practically like dumping your brain onto a disk "

Instead of scribbling notes on a memo pad while on the phone, Laizure types in information stores it, and prints out a hard copy for her secretary. "I don't even have to go through the added pain -- and neither does she -- of trying to decipher my writing," she says. If she needs to call a person whose name she has filed away, she asks to see the appropriate index, presses the "J" key, for "jump," to find the correct name, and hits "A," for autodial to get the number. Her computer, equipped with a Hayes Smartmodem board, dials as soon as she hits "P." The entire procedure takes 10 to 15 seconds.

Then there is the calculator. Talking on the phone to a printer or media person, for instance, Laizure will enter the specifications of a job, calculate them, add markup, taxes, art, and type, then hit function key J to bring the value of one of eight registers to the screen. "I've got a complete quote done before I'm off the phone," she says. "I can get a hard copy, somebody can come by and pick that up, the secretary can mail it out, [or] we can file it." "People," she adds, "have these computers sitting on their desks, and they have a numeric key pad, and they essentially never use that function as a calculating device. And those are the things that you really do day-to-day. You calculate, you phone, and you write down information."

While The Desk Organizer's slightly slow speed is, for Laizure, a minor inconvenience, others find the program's slowness unacceptable. Marty Winston, for instance, who uses both Shoebox and Time Manager, tried The Desk Organizer and decided against it. "It seems to use more of my time than it saves," he says. Winston usually prints out his schedules, then tucks them in a binder that he calls his war book -- a system he finds particularly effective when he is on the road.

Of course, for anyone who travels frequently, The Desk Organizer -- or any other program that claims to put your schedule at your fingertips -- has one whopping drawback. You can't take it with you. That is why Conceptual Instruments's Collopy doesn't use his own product for jotting down formal appointments away from the office. "I write those down by hand in a good old daytimer," he says.

Radio Shack tried to provide a partial solution to this dilemma with its TRS-80 Model 100 portable computer. Besides building in word processing and Basic software, its designers included a calendar function for scheduling appointments, a name and phone number directory, and automatic dialing capabilities.

George Hayles, who uses his Model 100 to write articles and letters when he is not at the office, also thinks it is handy for quickly locating names and telephone numbers. But as far as scheduling and reminders go, the software, he says, is nowhere near as capable as Shoebox's. "I wish I had [Shoebox] running on my Radio Shack 100," he says. "That would be ideal."

In November, Convergent Technologies Inc., in Santa Clara, Calif., began shipping its WorkSlate, a three-pound, battery-operated computer that the company thinks will handle any contingency a businessperson might meet. Besides providing a versatile electronic spreadsheet and calculator, it is targeted, says Convergent spokeswoman Karen Toland, toward managers and executives "who have notes written on the backs of business cards, napkins stuffed in their pockets, and little yellow tags stuck on everything."

Touted as a complete executive tool, WorkSlate can function as a dictating unit, speakerphone, automatic telephone dialer, telephone answering machine, communicating terminal, calendar, memo pad, expense recorder, and Rolodex. And you can do many of these tasks simultaneously -- record a phone conversation, use the speakerphone, and take notes, for instance.

The machine even works while you sleep. If you enter an appointment, press the alarm key, set the timer, hit the "do-it" key, then nod off, WorkSlate will shut itself off after five minutes to preserve its batteries. Still snoozing when its time for your appointment? WorkSlate turns itself back on and beeps you awake.