A few weeks ago a friend cornered me over a taco and asked some questions about the uses of personal computers in the home. The answers to those questions, it turns out, are pretty instructive about desk-top computer potentials and pitfalls for ordinary people like you and me.

My friend, it seems, dreads grocery shopping, so he wanted to know whether a personal computer could a) keep an inventory of every grocery item he has, b) inform him when it is time to shop because stocks are low, and c) print out the shopping list of needed items in the order by which he normally encounters them as he walks the aisles of his local supermarket.

Simply speaking, the answers are: "yes," "yes," and "yes."

But before you start dreaming about how a personal computer is going to revolutionize your shopping habits, consider these rather imposing problems.

First, to get your computer to do any one of those things, you'll have to develop your own computer home inventory and sorting program. That means you will either have to know a computer language such as BASIC or be able to figure out how to modify a commercially sold business program (cost: $200) so that it can accomplish what you want it to.

Strike one.

Even more imposing is this: For the program to work you'll have to type into the computer's memory every teaspoon of sugar you put in your coffee and every sheet of toilet paper you use just so your machine can keep up with your own brand of consumerism.

Strike two.

Finally, you'll have to obtain a copy of your store's aisle plan and then constantly update it because it will probably change from week to week.

(Interestingly, my friend went so far as to call his neighborhood chain supermarket to see if such a floor plan existed. Apparently one does, but local outlets often change it to suit their needs. More intriguing, however, is that my friend discovered that he was not the first to ask about obtaining such a floor plan for computer shopping-list sorting purposes.)

Strike three.

But before we write off personal computers as a total loss when it comes to grocery shopping, let's consider this scenario:

You turn on your computer, which is hooked up to a phone, and have it dial the number of your local supermarket. Then you call up an order blank, fill out your shopping list--the store's computer asking at appropriate places what size or quantity you want--and request a total. Finally, you type in your personal charge code and your computer prints out an itemized receipt.

A half an hour later, after watching the ball game or washing the dishes, you drive over to a window and pick up your order. With the time you saved you can gripe about the impersonality of it all or watch the second half of the game.

So far as I've been able to learn, no one is developing such a system right now (someone will let me know if I'm wrong, you can be sure of that), but most people familiar with the burgeoning electronic information industry say it is only a matter of time, perhaps as soon as five years, more likely 10, before it comes to pass.

That's why I said in the last column that it is here, in this "interfacing" between the home and the rest of the world, that the true power and value of home computers may eventually be realized.

When you start talking about the outside world, you're talking about networking and databank services.

Networking is really nothing more than a system whereby individuals with computers can link up so that they can send letters and messages to each other--a sort of electronic mail, if you will. Databanks are computers to which many people can gain access at the same time--via phones, for instance. These databanks contain all kinds of useful (and maybe not-so-useful) information.

Because of the importance of phones in this area of personal computer utilization, some people are calling it "telecomputing."

At least three telecomputing systems are in the field. One of them, The Source, is based in McLean. Another, CompuServe, is in Columbus, Ohio. The third, Dialog Information Retrieval Service, is a California-based operation.

What they offer is everything from electronic shopping restaurant guides and networking to banking and access to newspapers and up-to-the-minute wire service reports.

We'll talk about the costs of these systems in the next column.