GIANT FOOD is taking the plunge. It has decided to stop putting prices on each item in its supermarkets in the expectation that its customers will share its own faith in the computer.

This step was inevitable once the supermarkets went to computer-fed cash register and those little devices that scan the manufacturer's code on each item. That code tells the computer what it is you are buying, and the computer then tells the register what it costs. By relying exclusively on those codes, Giant can eliminate the cost of labor for putting labels or stamps on each of thousands of items. That savings will give it more profit in a notoriously low-profit business or a slight price advantage or, more likely, both.

But what about the consumer? Gaint says it will improve shelf markings so consumers can tell at a glance what each item costs. Will that be enough or will customers go elsewhere for the item with the price on top?

Our guess, like Giant's is that most customers will be content with a better shelf-price arrangement as well as a receipt that tells you what you bought instead of providing, as it used to, a long list of what sometimes seemed to be random prices. All that will be missing will be the ability to pick up an item at home and compare its written price with the price on the one you bought today.

If customers don't take to this new system, however, Giant will know rather quickly. In that event, you can bet that the prices will go back on the items.But given this particular food chain's past success with innovation, the odds favor a quick change instead by the other supermarkets. They can't afford for long to give a competitor that fraction of a cent advantage the no-label, no-stamp system will provide. If that happens, all those cans on your pantry shelves will soon be priceless.