Now, computers to take along on that business trip

For the executive on the go, what could be more useful than a portable computer? Use it on the plane, in the hotel, even while relaxing at the beach.

Or so goes the thinking of many computer manufacturers around the country. Dozens of companies are coming out with portable computers offering different capabilities and functions. They're all aimed at what the computer industry sees as an untapped market with almost unlimited potential.

The smallest can be held in the palm of your hand, and looks like a calculator. The largest ones weigh in at 39 pounds, and after a day of lugging them around you may well question the use of the word ''portable.'' But as their makers point out, all of them will fit under an airplane seat.

More than a year ago, the Osborne Computer Corporation of Hayward, Calif., came out with the Osborne I, a portable computer about the size and weight of a portable sewing machine. It retails for $1,795. Since Osborne entered the market, producers like Micro Source Inc., Extec Corporation, and Otrona Corporation have come up with variations on the Osborne theme, producing computers about the same size, but priced a bit higher.

Some of these portable computers feature built-in printers. Some have full-size display screens showing 24 lines of 80 characters each. And they come with various software packages which the manufacturers hope will catch the eye of the business community.

Most manufacturers aim to provide the basic computing functions of an in-office computer: some word processing, accounting, calculating, and time-management functions. Some even offer graphics. Most are capable of sending and receiving information from a company's mainframe computer.

Manufacturers turning out hand-held units include the Panasonic Company, Axlon Inc., IXO Inc., and Lexicon Corporation. These computers are mostly used to hook up with various data bases. Most have minuscule keyboards and one-line displays. On some, information is read ticker-tape style as it dances across the display. Most can run on batteries. Prices range from $300 to $1,000.

The data base hookup ability is popular, since it allows a user to get information from his company data base. It also allows access - through a phone line - to news, stock quotations, economic surveys, and even weather and sports in data bases such as the Source, CompuServe, and the Dow Jones News/Retrieval Service.

Some of these smaller models offer a host of peripherals, or ''extras,'' ranging from miniature printers to an adapter making it possible to read a full page of text on your hotel room television.

The Teleram Communications Corporation of White Plains, N.Y., says its new product is a happy medium between the bulkier Osborne and the limited memory capabilities of hand-held computers. Teleram, billing its own as the only truly portable computer, will begin to market the T-3000 next month. This model weighs less than nine pounds and snuggles into a briefcase, and it can operate on rechargeable batteries for several hours. The base price is $2,795. Other companies are expected to follow in Teleram's footsteps.

As a whole, makers of portable computers claim their machines will perform a wide range of functions. Salesmen will be able to place their orders and keep track of inventory as they travel. Businessmen will keep up with electronic mail and banking. They'll make airline reservations and know the latest real estate listings. They will get statistical analysis and credit verification, and even be able to send telegrams. And they'll whip off memos like there's no tomorrow.

But do people in business really need the services offered? Fred Withington of Arthur D. Little Inc., a technology consulting firm in Cambridge, Mass., says that manufacturers ''are not really addressing the problem.''

''Not that many businessmen need computing services when they're on the road, '' he says. The real need is for better communication services such as electronic mail and data retrieval. Mr. Withington thinks there won't be a very large market for portable computers ''until better support systems are available for the hardware.''

GRiD Systems Corporation of Mountain View, Calif., is one company which, in Withington's view, is confronting the problem. According to GRiD's director of marketing communications, Barry Margerum, it didn't plan a portable computer. It sought to make a computer with all the functions a manager would need, and then to make that portable.

The result is a sophisticated nine-pound computer with a versatile software package. GRiD claims it will provide a wide range of communication services. The price is less portable - a hefty $8,150.

Steven Epner, founder of the Independent Computer Consultants Association in St. Louis, says that ''in our mobile society mobility is becoming more expensive , and communication needs are increasing. The productivity potential is tremendous.'' But he doesn't know how well these new portable computers will fill the gap.

Jean Orr, a vice-president for research at Smith Barney, Harris Upham Inc., a brokerage firm, says that with so many new portables available, ''it's too early to see which will be the winners.'' Only the marketplace will tell which computer manufacturers have adequately anticipated and filled a legitimate business need.