Wouldn't you know they'd blame a computer? Even before the final bell had rung on Wall Street's "Black Monday," the instant analysts were rounding up suspects to blame for the 508-point drop that marked the biggest one-day decline in the history of the stock market. Not surprisingly, one of the chief culprits was that all-purpose electronic scapegoat of the age, the computer. The crash was the result of "computerized panic," The Wall Street Journal said. The president of the Pacific Stock Exchange blamed the market's disastrous day on "inhuman machines."

It's true that major financial institutions have been using computers to assist them in pursuing complex market strategies known as "program trading" or "computer-assisted trading." And it is not only the Wall Street giants who use computers to play the markets. There are also all sorts of stock market programs and information banks -- some of them awesomely sophisticated -- available to investors equipped with nothing more than a personal computer like the one that you have on your desk.

But the suggestion that computers caused, or even contributed to, the crash reflects a fundamental misunderstanding of the role of the computer in our modern world.

The computer is a tool, on a par with other tools like the pencil, the screwdriver and the dishwasher. It can do only what humans make it do. It can enhance human feats and foibles, but it does not cause them. To say that the computer caused the Wall Street crash is roughly akin to saying the screwdriver caused World War II. After all, the Japanese used screwdrivers to build their bombers, and without bombers there would have been no Pearl Harbor raid, and so on.

Before the politicians and the regulators go on a witch hunt to slay the beast called "computerized trading," it might be useful for them to learn what the term means. In essence, it refers to Wall Street applications for two familiar features of the computer revolution: high-speed electronic communication from one computer to another, and high-speed number crunching.

The big financial institutions do this work on fairly big machines -- IBM 3850 midsize computers or larger. They receive constant reports from several securities markets -- the Chicago Mercantile Exchange, the New York Stock Exchange, the American Stock Exchange, etc. -- and constantly compare prices, looking for the best time and place to buy or sell particular packages of stocks.

The computers can be programmed to ring bells or flash lights to signal the optimum time to sell a particular contract on a certain exchange. But these "inhuman machines" don't decide when to buy or sell, any more than an alarm clock decides when you should wake up. The clock and the computer ring their bells only because some person has programmed them to do so under a given set of conditions.

Not many individual investors find it worthwhile to spend the time and money to set up the same intricate program trading functions. But hundreds of thousands of personal computer owners use their machines to track and analyze market data. The opportunities available, even on simple home computers, are stunning.

Lotus, the big Cambridge, Mass., firm that publishes one of the world's most popular programs, 1-2-3, offers a long list of investor-support products. For the trader who has to know what's going on in the market every second, there is Lotus Signal. Signal is part hardware -- an FM receiver that hooks into the modem port of any MS-DOS computer -- and part software -- a program that pulls market quotes out of that receiver and can manipulate the numbers. Signal, for example, can ring an alarm if shares of XYZ Corp. drop below 20; it can give you minute-by-minute recalculation of your total portfolio as its value fluctuates with market swings.

For the investor who doesn't need "real-time" (that is, instantaneous) market data, Lotus sells a weekly financial data service called "One-Source." The One-Source subscriber gets a Federal Express package each Monday morning with a CD-ROM disk full of securities data. Data from Signal and One-Source are distributed in a form that makes it easy to plug them into 1-2-3, letting an investor manipulate the numbers as needed.

These Lotus services are not cheap, but a lot of serious investors find them worth the cost. For the investor on a budget, an outfit called Compustock (Box 130, Bountiful, Utah, 84014) offers somewhat less ambitious market data service at a fairly low price. Compustock is a financial data-crunching program, permitting a broad range of manipulations and comparisons of corporate and market figures. The program costs $60; for another $200 a year, you get monthly updates (mailed on floppy disk) of performance figures on a group of stocks of your choice.