If you are one of those people who think that half a loaf is better than one, and that the recent supermarket development -- two slices of bread wrapped in cellophane -- best of all, do not read on.

This is for people who think in terms of 25 pounds of flour, or gallon tins of olive oil. Such quantity buying saves a great deal of money if you entertain a lot, or if you invite the 300 people you owe all at one crack.

Heaven, for anyone who wants to buy in large quantities, lies in the area of Fourth, fifth and Morse Streets NE, a sprawling concentration of shops, stalls and warehouses known as the Northeast Market.

A stroll up Morse Street will take you past Chan's Market, at 505, where you can buy rice, onions, sugar, salt or flour in 25- to 50-pound sacks, or lay in a gallon of Kikkoman Soy Sauce at $5.50 for your next Chinese banquet.

The other day, Kramer and Sons at 515 was offering a 40-pound box of chicken wings for $27.60, or a 30-pound box of spareribs at $42, just the thing to use up all that soy sauce.

Onward and upward to Litteri's, where one gallon of Progresso olive oil sells for $12.50; Madre Sicilia for $13.50, and other brands for as little as $8.95 a gallon. Even if you don't enterain often, it's still a good buy and can be decanted into smaller bottle for easier use.

There also are capers by the quart, the tiny nonpareil at $7.75, or the larger ones for $5.75.

With Parmesan cheese selling for almost $12 a pound most places, Litteri's price of $2.69 a pound for an entire wheel seeems incredible. (It is, in that a whole wheel weighs almost 17 pounds.) That's the kind of bargain you can take advantage of only if you are going to throw the word's largest pasta party, have an insatiable lust for Parmesan, or have a large group of friends who would like to share. More easily disposed of is a 5-pound block of Mozzarella at $1.69 a pound.

At 523 Morse is WM. pence Co., where 10 pounds of fresh turkey parts cost $6.50 ($4.95 if you buy them frozen), where yo can find pigs' feet, large bags of soup bones, Virginia hams, whole, half or slices, 5 pounds of fresh chicken liver for $2.89, or the same amount of chicken backs and necks (for making stock) for $1.

Fifth Street is lined with doorways which lead into dark, chill warehouses.

They may look intimidating, but venture in and tell them what you're looking for. I have bought flats of cherry tomatoes and crates of tiny eggplants at prices which make the search worthwhile.

Fifth Street also is the site of an indoor market which covers almost an entire block (again, it is unmarked, so ask). Independent vendors sell produce, meat, poultry, eggs; there is even a stall selling voodoo items. Behind the indoor market is an outdoor one where occasinally there are live fowl and, once at least, an extremely large turtle.

If you persevere and don't let yourself be put off by the endless comings and goings of trucks and the dashing about of small carts, you usually can find a place to park. The central indoor and outdoor market behind it are open all weekend, and some of the shops keep Saturday hours. But the market is best visited during the week.