Draw a mental picture of the restaurant owner or manager: "Well dressed, well fed, wearing a welcoming smile and a gracious manner," you suggest.

Look a little closer. The paunch may be real enough, but there's a good chance the collar will be slightly frayed or the suit in need of pressing.The smile is straight from central casting, there is a slight tick in an eyelid -- caused by fatigue or worry or both -- and the gracious manner may just be an outward impression given by someone too preoccupied to concentrate.

It appears to be such a glamorous life that no one feels sorry for the restaurateur except himself. As he (or she) sees it, the "middle man" who operates a restaurant business isn't the one who buys low and sells high; instead he takes the heat for mercenary suppliers and inept cooks on one side and rude, uncomprehending patrons on the other. These customers are oblivious to his best efforts and usually complain from ignorance rather than enlightened concern.

This is exaggeration, of course. There are restaurateurs who are happy in their work. But most of those who populate the world of restaurants do feel themselves misunderstood and often mistreated.Furthermore, for fear of offending a fickle public, few of them will speak out, even in the face of outrageous behavior.

One evening I encountered a maitre d' of my acquaintance in some pain. He had just been kicked in the groin by an angry (and drunken) customer who had forgotten to have a parking ticket validated and had been forced to return to the restaurant.

That's not normal, but broken reservations are. So are people who ignore reservation times or dress codes at will, who steal china, silver, table appointments and even bits and pieces of the decor.

Pity the poor restaurateur. When he takes steps to improve quality, his customers argue about price. When he introduces something new to the menu -- an exotic dish or a classy domestic wine, they ignore it until it disappears, then complain about being offered only "the same old things."

Also, although only the help complains about it, he too, works lousy hours and sees home life suffer for it.

Sooner or later, he may become cynical and develop a severe case of contempt for the customer, a dangerous disease that some feel can be found in epidemic proportion among the French restaurant community.

It's not all one-sided, though. There are restaurant operators without talent, taste or any sense of public relations. There are restaurants, some of them financially successful, so flawed that Laurel and Hardy's best efforts could scarcely disrupt the dining room. There even are people in the business filled with malice and evil intent. The industry hasn't done much to curb its cheaters and frauds, but neither have the medical or legal professions.

At some point, perhaps, during the 200 years or so public eating places called restaurants have been urban institutions, there was peace and harmony.But I doubt it. There were, however, fixe hierarchies in the dining room and kitchen. Waiters were not too proud to serve attentively and skillfully; journeymen cooks knew their craft thoroughly.

Today the owner or manager lives constantly with uncertainty. A restaurant is an expensive business to run and one which requires a consistent short-term cash flow. Only a few weeks of slack business can disrupt projections and cause serious problems.

"We have a difficult situation," Francois Haeringer, the widely respected owner of Auberge Chez Francois, once said. "You just shrug if the shoe or television repairman tells you it's not ready, to come back next week. But we must be ready twice a day, at 11:30 and 6, no matter what's happened. No excuses will do."On the other hand, I've yet to encounter a situation where a note on the menu announced "50 Percent Off Today" because two cooks didn't show up, inferior cuts of meat were delivered, the air conditioning failed and the maitre d' was hung over.

There is constant concern with the cost of food, labor and rent, three of the four horsemen of what consumer specialist Sidney Margolius has called "the inflationary apocalypse."Net profits, according to several owners, aren't what they once were and the pot seems even smaller if it is shared among several partners or part of it goes to the chef or maitre d'.

The restaurant operator may feel himself caught in a vice on several fronts.

To save labor costs and keep prices down, he turns to prepared foods. Then the consumer demands fresh. Back come the extra cooks and close behind them is the health department, much more likely to find violations in restaurants where extensive "hands on" preparation is done. (A French chef once told me with irritation of a health inspector asking him what a cook was doing with a product he didn't recognize. "The cook was checking mussels to throw out any that were bad," the chef said. "And this guy is marking me down because there are cracks in my floor.")

To the customer, the kitchen is a place apart where men in tall white hats perform culinary miracles. To the owner, it is a shadowy world filled with members of a medieval cult. In hiring them recommendations and background are meaningless. Cooking is a craft, but there is no exam, no rating system. A skilled technician may prove to be a dreadful administrator -- a cook but not a chef. There are personality conflicts within the kitchen, arguments about art versus economy, and opportunities for loss, theft or inefficiency that can send food costs skyrocketing. Few survive in the restaurant business who don't know the back of the house or learn it.

It is no wiser to feel secure about waiters and barmen.They, too, have opportunities to take advantage. Furthermore, being in direct contact with the public, they can hurt the restaurant's image with a bad attitude, by inattention to duty or by being untidy or unclean. They are not being paid much, so a fall off in business or miserly tipping will drive them elsewhere. (To restaurateurs, the ideological question of why customers should be expected to tip is moot. That's the way it is, they say. If the customer didn't pay a tip, he or she would have to pay through higher prices on the menu, which -- they claim -- nobody wants.)

The public blames the restaurant, not its suppliers, for slippages in quality, for menu items that are not available and for sudden jumps in price. The need for careful supervision of deliveries and the need to do battle in the face of inadequate provisions are other strains that aren't supposed to show in the dining room.

What of the menu? The old-line restaurant operator sees it as an advertising and sales tool for him, not an information sheet for the consumer. After all, he pays to have them printed. So if customers are used to such romantic notions as "spring" lamb or chicken, "Roquefort" instead of blue cheese or "homemade" pastry, what's the harm? Everybody does it, right?

Wrong, of course. Jack Cockrell, who heads the Restaurant Association of Metropolitan Washington, prefers the term "accuracy-in-menu" to "truth-in-menu" and hastens to point out that his association supports it and has worked closely with local authorities to promote it.

But, in the language of a menu, all of the above are served with the main course. They are part of the pangs of a business that those who stick with find exciting, challenging and ever changing. After a static period of seeming decline, young people have been coming into the restaurant trade once again. Eating out has become a national way of life. Questions of quality and style are raised, as they always have been, but the industry's future is promising.

What, then, do restaurateurs want? I judge it is not so much to be loved as to be fully appreciated. What drives the operator of the spiffy "table cloth" restaurant up his damask-covered wall is a customer flatly stating that such and such a dish is "too expensive" or complaining that he can buy pasta cheaper elsewhere.

People who glory in an "all you can eat" menu should realize, they point out, that no one is subsidizing such free-style gluttony. The restaurant involved must make a profit (unless it is on a kamikaze flight or being used as a tax write-off) or it won't be open next week. Somewhere along the line corners are being cut.

The thoughtful restaurateur doesn't object to such places. Diversity is one of the strengths of his industry. But he would be pleased if the customers would look beyond prices on the menu or the volume of food on the plate and consider his entire operation.

Begin with the physical plant. Is it in a high-rent district? Is it well kept up? Is there a parking lot attached or valet parking? All this costs money.

How about the decor and appointments? Homeowners know how much bathrooms, carpets and antique lamps cost. If the restaurant sports the real thing, credit the owner with taste and a willingness to spend money to create that illusive quality called ambiance.

Look at the table, the chair you are sitting in, the silver, glassware and flowers. Are they distinctive? Are they real? It takes time and more than a few extra cents for a portion of "veal francais" to pay off such investments.

Does the restaurant advertise? Is there a lighted sign outside? That costs money. So do waiters' uniforms. How many serving personnel are there? Do they know their jobs and the menu? Are they well supervised?

Last, but not least, what about the menu items? The day when a restaurant was respected for the length and breadth of its selection has passed. People mistrust -- rightly, I think -- a restaurant that offers something of everything. But is the food fresh? How much of it is made on the premises? Are the preparations complex enough to require specialists in the kitchen? Are there daily specials? A made-at-the-table Irish coffee or steak tartare may be high-priced, but you can't hide the ingredients, and the time involved plus the show should be worth something.

There is, of course, the risk that real whipped cream -- on a drink or in a restaurant -- will mask a lack of substance beneath. There is also the human reality that different people look for different experiences when they dine out, and that for many absolute food quality is not the prime consideration.

It is, as they say, a tough business. CAPTION: Illustration 1, no Caption, By Don Carstens for The Washington Post; Illustrations 2 through 5, no Caption, by John H. Bowen from Menu, Copyright (c) , 1978 Robert N. Hills