A personal computer is a wonderful tool for managing your investments. Using a computer, you can evaluate stock and bond portfolios, chart commodity and option trends, or compare real-estate tax shelters. You can gather information about potential investments more quickly than you ever dreamed of, then subject your data to the kind of analysis that until recently was the province of the pros. Up-to-the-minute performance evaluation. Statistical summaries and graphs. Projection and comparison of alternative purchases.

Sound like fun? Sure, you say -- if I didn't have to work.

The objection is not trivial. Managing your investments on a computer may produce profits -- some day. To reach that point, you will have to spend a considerable amount of time figuring out which programs might be most helpful, learning how to work them, then actually putting them to use. If time is money, computerized investing is an expensive proposition.

Still, putting your portfolio on a computer now gets you in on the ground floor of a field that is likely to burgeon in the future. Although most investment-management software at the moment is relatively primitive, programmers are already at work on easy-to-use yet sophisticated tools that should broaden the reach of the personal computer immeasurably. By the 1990s, successful investors may find themselves willy-nilly in one of two camps: those who make money through computerized analysis, and those who make money because they are lucky.

Then, too, computerized investment management can be an engaging hobby. "For most people, it's probably not cost-effective," observes Tom Meyers, president of the American Association of Microcomputer Investors Inc. "They're doing it because they find it interesting -- they want to be able to turn on the computer and see how their stocks are doing."

Essentially, a computer helps you with two tasks. One is keeping track of your portfolio: what you have bought and what you have sold, how much it is worth, how much you have made or lost. The other is helping you figure out what to buy or sell next. Amid the bewildering array of investment-management software that is available, it is helpful to keep these two categories in mind. Most of the programs are simply variations on one theme or the other.

Portfolio-management programs range widely in price, but most work on the same basic principles. You enter your assets and transactions -- what you buy and sell, at what price, and so on -- and the program takes over from there. The simplest programs let you record and update this information, and provide you with a profit-and-loss statement that you can use at tax time. More complex programs offer any number of fills, many of them useful. Blu Chip Portfolio Manager (XOR Corp., Minnetonka, Minn.; $79.95) uses a spreadsheet format to show your portfolio and its tax implications. The Computing Investor (The Computing Investor, Marana, Ariz.; $99) allows "weekend investors" to update and study charts and portfolios on a weekly rather than a daily basis.

As with most purchases, the trick is to figure out what you need. Do you want to keep track of short sales, margin loans, or assets other than equities? Do you want to know your annualized percent gain or loss for each holding? Do you care how your stocks are doing by industry, or what your portfolio's overall P/E ratio is? Programs can be found that provide all this information in various combinations. Most intriguing -- although relatively expensive -- are programs that let you update your portfolio automatically, from electronic stock-information services. Portware (Portware Inc., Edina, Minn.; $195) can retrieve price updates from any of several on-line databases, keep track of portfolio values and transaction lots, and generate reports on your holdings. Dow Jones & Co. offers a package of programs, one of which, Market Manager, allows you to maintain and analyze your portfolio and to communicate with Dow Jones News/Retrieval (Dow Jones & Co., Princeton, N.J.; $299).

Fundamental analysis software, in principle, performs the service traditionally performed by brokers and securities analysts, albeit in somewhat different fashion: It searches the investment universe for good buys. To accomplish this end, a program may either screen many equity groups or evaluate selected stocks in depth. The best-known programs are in the screening category. Standard & Poor's Stockpak II, for example (Standard & Poor's Corp., New York City; $275 to $1,010, depending on the range of stocks included; all programs come with monthly updates for a year), includes much of S&P's library of financial facts on some 4,500 companies, and can be screened for combinations of fundamental indicators in less than a minute. Value Screen (Value Line Inc., New York City; $495, including 12 monthly updates), which Value Line founder Arnold Bernhard attests crams 32 of his key variables onto a disk, provides information on all 1,650 companies followed by Value Line. You can screen these stocks either by Value Line's variables or by your own.

The in-depth analyzers are more diverse. One program may accept all the standard figures from an annual report, then print an evaluation of the company; another may ask for the very latest operating results and project figures for the next quarter; a third program may compare the various corporate ratios of companies you hold or are interested in, and rank them by fundamental strength. Here, the trick is to know what you are looking for, then find the right program.

Market Maverick (Financial Software Inc., Chardon, Ohio; $275, plus $120 for monthly data disks for one year) is a well-liked program for projecting future value from past earnings, dividends, and growth rate. The Evaluation Form (Investor's Software, Bradenton Beach, Fla.; $100) automates the analytic procedure developed by the National Association of Investment Clubs: It prompts input of over three dozen items about a company, then prints a tightly formatted two-sheet summary of the company's fundamentals, with estimates of probable price ranges. Stock Price Forecast (J.R. Software, Florissant, Mo.; $135) also uses past earnings/dividends and economic indices to project a target price. For an intense (and more expensive) monitoring of holdings, there is microDISCLOSURE (Disclosure Inc., Bethesda, Md.; $250), a package that puts an IBM Personal Computer on-line with a database of Securities and Exchange Commission filings, allowing custom creation of ratios and reports on the latest fundamentals of most companies.

Technical analysis software is more specialized than other investment-management software. Technical analysts -- "elves," as they have come to be known through the television program "Wall Street Week" -- are investors who chart and analyze a host of statistical indicators, trying to read the market's direction on the basis of what it has done in the recent past. Those who spend hours constructing their charts by hand will find that a chartgenerating program is worlds ahead of graph paper. Even so, keying in new information can take hours, especially if you want to keep more than one or two charts daily. And if you download your new information automatically (using a modem and telephone to hook up to a national database), you will pay hefty connection fees, and you may find that some of the information you want isn't available. The cost of keeping just a few charts current can add up to the cost of a commercially available weekly chartbook that keeps hundreds of charts, with many times the data your computer will show.

To the confirmed chartist, of course, these objections will seem nonsensical: The important thing is to plot one's own configuration of statistics, not someone else's. Among the software packages that are worth looking into are Dow Jones Market Analyzer (part of the package mentioned above), which incorporates 17 different graphic tools; The Technical Investor (Savant Corp., Atlanta; $395), which combines database communications, charting, and technical analysis in up to four separate "windows" on the computer screen; and Wall Street Window (R&D Software, Reston, Va.; $395), a top-of-the-line program for the IBM PC and the IBM PC-XT that offers full-year daily graphs, Dow Jones quote interconnect, and a spreadsheet interface.

A few special programs support neither the fundamentalist nor the technician, but "opportunist" investors, who track the behavior of traders, insiders, and other investors. Market Mood Monitor (Computer Asset Management, Salt Lake City; $185) watches "sentiment indicators" like public short ratios, advance/decline lines, and premium/discount figures on futures. Market Trend Analysis System (Personal Equity Computing Inc., Ocean, N.J.; $350) claims to incorporate indicators that project "action of the smart money" in stock, options, and money markets.

Then there are the programs, some of them among the most interesting on the market, that are hard to categorize. A retired airline pilot named Carl Vietor, for example, has spent two years constructing a buy/sell analyzer, Compu-Cast (Compu-Cast Corp., Los Angeles; $325) whose 27 subprograms, with a master menu, measure a stock's critical turns. Vietor claims rather spectacular trading results with it.

Finally, some new programs allow what might be called "virtual diversification." Most investors wish they could own more equities than they can afford, and most portfolios would benefit from greater diversification. But even where substantial diversification is impossible, a program can be constructed that compares one eqity with others, weighing the stocks you actually hold against those you would like to hold. If this process of virtual diversification is carried out continuously and conscientiously -- and if stocks are switched now and then to achieve the balance indicated by the program -- you benefit from the collective action of all the stocks being compared.

Keeping up with the mushrooming field of computerized investing is difficult: There is almost too much information available. But if you have been bitten by the bug, here is where to turn for additional material:

Financial and Investment Software Review, 11 Hanover Square, No. 1302, New York, NY 10005. This bimonthly journal is co-sponsoring MICRO INVES/TECH' 84, a major exhibit and conference on investment software in New York City on November 8 and 9.

Wall Street Computer Review, 150 Broadway, New York, NY 10038. This monthly, aimed mainly at investment professionals, includes ongoing directories of various software categories.

Computerized Investing, American Association of Individual Investors, 612 N. Michigan Ave., Suite 317, Chicago, IL 60611. This group also runs the Individual Investors electronic bulletin board, a phone link that connects members' own computers with one another through the organization's national headquarters.

American Association of Microcomputer Investors Journal, PO Box 1384, Princeton, NJ 08542. Membership in this group brings the bimonthly journal, listings of public domain programs, and quarterly updates on a directory of hundreds of investment programs.