By day, he pilots his company through production snares and personnel conflicts. By night, flanked by two comrades, he hunches over his IBM Personal Computer, charting a course that will uncover treasures buried deep in an underground cave. Like many chief executive officers, Bruce Williams, president of U.S. Tool Grinding Co., a 100-employee company in Desloge, Mo., plays microcomputer games. Unlike some businesspeople, he cheerfully acknowledges his habit. "It's just plain old fun," he says.

Estimating the number of entertainment disks bought by businesspeople for their own amusement is no easy task. "Probably in the neighborhood of 25% of executives have a game hidden somewhere in their drawers," says Dave Lee, owner of a ComputerLand store in Cincinnati. "You hear them talk to the salesmen about it when they're in the store on their lunch break. They don't seem to be proud that they're playing games. But I know they are [playing them]. I see the sales receipts."

The games businesspeople buy aren't predominantly the shoot-'em-up arcade types beloved by their sons and daughters. Nor, though they take advantage of computer memory and capability, are they played with paddles, joysticks, and the other paraphernalia that convert Apple computers into video arcades. In fact, the most popular entertainment program is, strictly speaking, no game at all.

Flight Simulator, published by Microsoft Inc., is "at the top of the list," says Ed Murphy, software-product manager for ComputerLand Corp. in Hayward, Calif. The program lets users "fly" a Cessna 182 Class airplane in "real time"; that is, it takes as long to go from Meigs field in Chicago to Willard Airport near Champaign, Ill., say, as it would in an actual airplane. The program allows users to operate in three modes: "easy flight"; a reality mode," where you have to worry about such details as running out of gas; and a World War I British Ace war game.

To fly right with Flight Simulator takes more than a little concentration. Patricia Asch, president of MicroImage Inc., a microcomputer consulting firm in Georgetown, Conn., pulls out her copy whenever she gets frustrated working. But, she says, the difficulty of the program generally imakes her frustration worse. "My brother's a pilot, and he adores it," she says. "But I crash continually." Still, she is hooked. "It's so realistic. That's what I love about it," she says.

Although Flight Simulator requires closer attention than some games bought by fun-seeking executives, it is not atypical. Many of the entertainment program that managers buy are "brain games," says Michael Backes, of Chess & Games Unlimited, a six-store, Los Angeles -- area chain that sells board and computer games. Generally, however, they don't buy these programs to give their gray cells a workout. The three primary reasons games sell to businesspeople, says Ed Murphy, are "entertainment, entertainment, and entertainment. Any other reason is strictly secondary."

Murphy does credit the "show-off impulse" with fueling some purchases, however. When businesspeople have a new computer, he maintains, they want something that can demonstrate to colleagues and friends what the machine can do. And, says Lee Davis, manager of Software Atlanta, a two-store retail software company, "showing your average cousin your latest Multiplan spreadsheet isn't going to impress him."

Bruce Williams makes no bones about finding games entertaining. When he brought home his IBM PC nearly a year ago, he played games for about 10 hours the first week. He enjoyed Air Traffic Controller, even though he killed 580 people in two hours. "I felt very badly about it," Williams says. He fooled around with Blingsplatz, an arcade-type program. "I didn't get much enjoyment out of that, because it wasn't a big challenge." But his hands-down favorite was the Microsoft Adventure game, a program in which players find mounds of treasure by solving a series of puzzles and riddles.

"When we first bought the computer," he says, "I would have computer parties. After we'd gotten the kids to bed, I'd invite two other guys over, and we'd work till two or three in the morning trying to solve the riddles of the game." Williams and his friends, a doctor and the vicepresident of a manufacturing company, played Adventure for two or three months, once or twice a week, before he moved his IBM PC to the office. "I guess we probably solved about 30% of the riddles until pressures of work and family took precedence over the game," he says. "There were some problems we spent five or six hours, sometimes several days, trying to solve." To track their progress, Williams and his friends kept a chart -- two big sheets of drafting paper covered with notes and maps.

But Williams found his game playing provided more than amusement. He remembers the day he walked into the computer store to pick up his new IBM PC. The salesperson, he recalls, suggested he sit down and play with the machine while the sales slip was being prepared. He looked at all the keys and realized that he had no idea which ones to push. "I thought, 'This is really distressing,' and I knew I had a long way to go to learn what to do with it." Playing games, he thinks, helped him over the hump. "You stick the disk in the machine," he says, "and it does something for you. You immediately get satisfaction."

Frank Sheahan, owner of Frank Sheahan Insurance, a six-person, San Luis Obispo, Calif., insurance firm, agrees. "I've heard that executives have literally retired early for fear that they may have to learn how a computer functions," he says. "But I think it can be a joy if you approach it as a new learning experience." Although adventure-type games hold no thrill for him, playing Millionaire, a stock market simulation program, helped him cozy up to his Apple. "If you can introduce yourself to [the computer] through games," he says, "it's not going to be that big monster that sits there and scares people. The more experience you have using the hardware in general, the more familiar you become with it."

The desire to ease into microcomputing helps account for the popularity of cine category of games -- those with which executives are already familiar. PC Man, a Pac Man knock-off for the IBM PC, was gobbled up by businesspeople, since it was one of the few arcade games that they knew; it is also a snap to play without having to read manuals. Avalon Hill Game Co., a 25-year-old game board manufacturer, which bills itself as "the thinking man's game company," has successfully computerized many of its classics. Its Microcomputer Games division, formed in 1980, converted such favorites as Acquire, Stocks and Bonds, and Facts in Five, as well as many of the company's popular war-strategy games. The division also developed several original computer games.

And the Friendly Ware PC Introductory Set, a package that includes electronic versions of such old standbys as Concentration, Othello, hangman, and blackjack became an immediate smash. In publishing one of the first game packages for the IBM PC, Ed Murphy points out, Friendly Ware was one of the few campanies to realize that businesspeople were not averse to fun. "The executives came in and, sure enough, they wanted to buy games," says Murphy. Because it had very little competition, the Friendly Ware Introductory Set was one of the best-selling programs for three months running.

Still, brain twisters remain the most popular game category with businesspeople. Infocom, a Cambridge, Mass. based company founded in 1979 by exiles from Massachusetts Institute of Technology's Computer Lab, specializes in adventure games and puzzlers. The game that gets the best reviews from his professional customers, says Software Atlanta's Lee Davis, is Deadline, Infocom's locked-room murder mystery. Zork I, a fantasy-type game modeled after Dungeons and Dragons and similar to Adventure, has been a best-seller for the company for four years, and the other Zorks, II and III, have also done well.

John Hodges, president of Harcomm Associates, a 25-employee advertising and marketing firm in Cambridge, Mass., thinks Zork is appealing, but he finds that it eats up too many hours. "I might be able to complete it," he says, "if I didn't have a lawn to mow and a business to run." Another Dungeon and Dragons -- type game, however, has kept his interest since day one.

Two or three evenings a week, Hodges sits at his TRS-80, Model III and dials up his electronic mailbox on the Delphi Network, an on-line computer service similar to CompuServe and The Source. A message is usually waiting for him -- or for his assigned character, an elf -- from the "dungeon master." Played against people all over the country, the game involves a quest for a magic ring. "It's pretty silly when you come right down to it," says Hodges. "But it's kind of nice recreation about four in the morning, those times when I find I have nothing else to do."

Hodges does all his game playing at home. Although he will soon be buying another TRS-80 for the office, he doesn't think he will indulge his hobby during business hours. "I feel guilty," he says. "I've got so many things to do, that I think I would have a hard time justifying playing with [the games.]"

Perhaps to assuage guilt feelings, a new crop of "businesslike" games has emerged in the past year. Executive Suite, the first program in Armonk Corp.'s Grey Flannel Fun line allows players to claw their way up the corporate ladder. Written by Blair Bryant, president of the Newport Beach, Calif.-based company and a 1978 Harvard Business School graduate, the game presents players with a number of thorny situations intended to test presidential timbre. Some of the choices, though humorous, are surprisingly true-to-life. "It was just like a real business environment," says Bruce Williams. "The things that get you ahead are not necessarily the things that are logical."

For those who would feel red-faced if their game playing were discovered by friends and colleagues, the program thoughtfully provides an escape hatch. Press the IBM PC's function key 5, and the screen is wiped clean. Press F6, and you are back, as it were, in business.

Frank Sheahan rarely feels compunction about playing his favorite game, Millionaire. A stock-market enthusiast, he finds the program helps him in devising investment strategies. That kind of learning experience, was, in addition to providing a good time, the intention of the grogram's author, Jim Zuber, head of reasearch and development for Blue Chip Software, a Woodland Hills, Calif., startup, that specializes in financial simulation games. In August 1983, Blue Chip shipped Tycoon, its commodity-market simulation game, and on the drawing board are Baron, which tackles the real-estate market, and Squire, a financial planning game.

At the beginning of each session of Millionaire, the program generates a new, 91-week stock-market "environment." Then players make decisions based on general economic news, industry trends, and factors influencing specific stocks. "If it says the auto industry is doing great this year, that will truly have a proportionate influence on auto industry stocks. You could never do that in a board game," says Zuber. "The key to success when you play it is just like the key to success in the real world," adds Blue Chip's president, Bob Slapin. "When you make money you feel great, and when you lose it, you are sick to your stomach."

To help his 14-year-old son, Matt, become familiar with the market, Sheahan turned him onto Millionaire -- to-good effect. But Matt's additional fondness for arcadelike games resulted in Sheahan's putting the computer off limits. Every time he came into his office, it seemed, his son was sitting at the Apple. "It became disturbing," he says. "It's hard to conduct business with these crazy sounds and games and the emotions he emitted every time something went right or wrong."

Whether or not the office turns into a game arcade is, clearly, becoming a new issue of the high-technology era. Now that Bruce Williams, for instance, has moved his IBM PC from his home, he hasn't touched an entertainment disk in a month. "Usually when I get into work," he says, "I have so much to do that I can't justify playing a game." But he misses those fun times huddled with his buddies in front of the IBM PC. "We still have the Microsoft Adventure game and the chart," he says wistfully. "And my friends keep saying, 'When are you going to have the computer at home, so we can start playing again?' "

1. Microsoft Flight Simulator (Microsoft Corp., Bellevue, Wash.). Realistic simulation of flight in a single-engline airplane. For IBM Personal Computer [49.95).

2. Microsoft Adventure (IBM Corp., Boca Raton, Fla.). One of the original adventure games in which players solve clues to find hidden treasure. For IBM PC ($30).

3. Millionaire (Blue Chip Software Inc., Woodland Hills, Calif. Playing the market without financial consequences. Blue Chip also publishes Tycoon (commodities simulation) and Baron (real estate). For Apple, Atari 800, IBM PC, and most MS-DOS and CP/M machines, including DEC Rainbow ($59.95; 8-inch format, $69.95).

4. PC Man (Orion Software Inc., Auburn, Ala.). A Pac Man knock-off. For the IBM PC ($34.95).

5. Friendly Ware PC Introductory Set (FriendlySoftInc., Arlington, Tex.). Familiar games for IBM PC including Othello, blackjack, Concentration, and hangman. For IBM PC ($49.95).

6. Zork (Infocom, Cambridge, Mass.). Fantasy game in which players search for treasure. Infocom also publishes Zork II and III ($39.95); Deadline ($49.95), a mystery that gives players 12 hours to find out who done it; Witness ($49.95), another mystery; and Starcross ($39.95) and Suspended ($49.95), science fiction adventure games. For the Atari; Apple; Commodore 64; DEC Rainbow; IBM PC; NEC PC 8000; Tandy Models I and III; TI Prof., 8-inch CP/M version*, DEC RT-11*, NEC APC.*

7. Stocks and Bonds and Acquire are among the 49 computer games for adults (Microcomputer Games Inc., a division of Avalon Hill Game Co., Baltimore). Stocks and Bonds for Apple, Atari 400 and 800, and IBM PC ($25). Acquire for Apple only ($25).

8. Executive Suite (Grey Flannel Fun, a division of Armonk Corp., Newport Beach, Calif.) A simulated climb up the corporate ladder. For IBM PC ($39.95).

* Versions for these computers cost $10 more.