Mayor Marion Barry says he, too, has frustrations in dealing with the District of Columbia bureaucracy, One involves a poster to promote a pet project, the city's summer jobs program for teen-agers:

"I've been trying for a month to get a poster that makes sense, and I haven't gotten a poster yet," Barry said the other day, throwing up his hands.

"There are some people who are just incompetent," Barry rambled on. "As I said to [acting labor director] Matt [Shannon] the other day, I said, 'Matt, if we can't get a damn poster out from a GS14, we ought to fire him or do something with him. I think the poster's just endemic to a larger problem."

In his first 100 days in office, which ended Wednesday, Marion Barry has come to learn the frustrations of a mayor who heads a bureaucracy that sometimes has problems performing the simplest of tasks.

Barry is confident that he has set a new tone of government and begun to address longstanding city problems. "I think people will generally concede that we've not yet made a dent in solving a lot of our problems," he said in a long interview last week. "But we've tried harder than ever before."

The trying has changed the style of government in the city. Publicly, there is more movement. Barry appears to insist that things be done right without cutting corners and imposing avoidable delays. He talks about solving longstanding problems. He makes proposals to cure the city's ills and aggressively forges symbolic partnerships with other area governments.

Although many in the city feel positive about the new mayor, the jury still is out on the question of how the initiatives launched during Barry's first 100 days will really change the city and its quality of life.

"You don't turn the world around in 100 days," said Metropolitan Washington Board of Trade President Oliver T. Carr. Others agree.

Trying to turn around city government has also changed Barry, the 43-year-old former strident black activist who for most of his life has been craving influence and power-first, from outside city hall and now from its highest office.

"I guess the awesomeness of the job has settled into me," Barry said. "It's an awesome responsibility to have decision-making power over people's lives or affecting people's lives. That's a sobering feeling."

And in the quiet of his office on the top floor of the District Building, Mayor Marion Barry sits in the high-backed brown leather chair behind a large glass-topped desk cluttered with papers. He is surrounded by the same dozens of green plants that kept him company during four years on the City Council.

The thinning hair in his salt-and-pepper Afro is slightly grayer. The girth inside the vests of his three-piece suits bulges, the result of abandoned efforts to slim down.

He insists on portraying himself as the consummate public leader and totally dedicated public servant. One minute he tells an interviewer that the only way he can rest from his work is to leave town-as he has done this weekend. "What do you do to relax?" the interviewer asks later.

"Work," Barry grunts.

"When you get tired of work."

"I'm serious. I work."

Barry's pastor and longtime friend, the Rev. David H. Eaton of All Souls Unitarian Church, says of the new mayor, 'He's been able to control his temper better. He's becoming a person who understands the positive aspects of patience.

"Marion used to be young, and brash and with very definite ideas. Ever since his campaign, he's learned not to promise more than he can deliver."

A. Knighton Stanley, a politically active minister who first opposed Barry's candidacy but endorsed him after Barry's victory in the Democratic primary, said Barry's real transition may finally be ending.

"A month ago," Stanley said, "it was wait-and-see. Now people have accustomed themselves to the fact that Marion is mayor. You hear people struggling to say, 'Mayor Barry."

The mayor crises the mayor has faced were mostly unexpected. He has had to contain thousands of unruly, protesting farmers, whose demonstrations gave Barry his first experience with mass demonstrations in the nation's capital. While Barry vacationed in Florida, almost two feet of snow fell unexpectedly on this city, halting cars, buses and subways and clogging streets.

Later, he would be confronted with a paralyzing 23-day strike by teachers. His personnel director would be indicted by a grand jury. Then a predawn fire would kill nine persons in a home, for outpatients from St. Elizabeths mental hospital, that city inspectors said afterward should never have been issued an occupancy permit.

Reflecting during the interview on his first three months in office, Barry said it was only the teacher strike that he would have handled differently.

"I shouldn't have waited a week to let them [the school board and the teachers union] meet and mess around," Barry said. "It might have been better to have started earlier . . . but that was just a matter of not knowing what the ingredients would be in such a strike."

Barry claimed credit for ending the strike and that won points for the new mayor, Stanley said. "Marion claimed a victory in the school strike. Nobody else would have done that. People ask me if he really did that and I say, 'I don't know.' But he claimed he did, and that it took guts."

Barry has been sharply criticized only once-for comments he made during the heavy snowfall. He asserted that city workers had done a "fantastic" job clearing the snow-even though many streets had not been plowed. "It's not a crisis," he told a reporter.

What about those who could not drive cars or take buses, the reporter asked. "They can walk," Barry said. When that was quoted in an article, people were enraged.

Last week Barry stuck by his praise of the snow-plowing job. The crisis in confidence was created, he said, by misperceptions presented in the reporter's story.

"What angered me most about the snow story," Barry said, "was the fact that I had been in contact with the appropriate people-even when I was in Florida . . . The criticism was that the people interpreted [the newspaper characterization] as a cavalier attitude."

Barry used his first three months in office to carry out some of his major campaign promises. He removed more than a dozen of the department heads and top-level aides whose alleged incompetence, he said, bogged down city government.

He presented proposals to double the number of summer jobs for youth, charged a task force with finding a way to reduce infant mortality and proposed a $35 million program to start "taking the boards off" 733 of the estimated 4,500 abandoned housing units in the city. Barry has other plans to help stimulate low and moderate income home ownership in the city.

In the next 100 days, Barry said, he wants to focus more attention on the troubled Department of Human Resources, the Department of Environmental Services and the Department of Corrections. He said he wanted to improve services in each of those departments but did not elaborate.

Since becomg mayor, many of Barry's days have become filled with dawn-to-dusk meetings with department heads and top aides.

"The reason I have tso many meetings is the fact that I am putting my personal imprint on the government," Barry said. The impression process is sometimes hampered, his alter ego and general assistant Ivanhoe Donaldson said, because the city bureaucracy is sometimes more incompetent than Barry had anticipated.

"What should have been a one-day project, now takes up 10 days of your time," Donaldson complained.

Donaldson said many of the department heads are simply not used to the new mayor's style and philosophy. Nor are some accustomed to writing anayltical reports, Donaldson said.

One department head described meetings with Barry and Donaldson this way: "They come at you from the point of questioning every single thing you say. They really interrogate you. You start out in a deficit and you've got to prove yourself."

Herbert L. Tucker, director of the Department of Environmental Services, smiled when asked once about the style of the new self-professed "competent and compassionate" Barry administration.

"It may be a compassionate hand," Tucker said, "but it's wearing an iron glove."

The satisfaction that Barry has received in the job is defined in large part by the unique set of values of the mayor-a Mississippi-born black man, raised in the segregated South. He seems determined to overturn the myths of inferiority that that system tried to foster.

"I believe in achieving and I believe in excellence as a personal philosophy. I just believe that," Barry said. "And I believe that what you do, you ought to do your very best."

He was proud, he said, to have found "capable and competent and committed blacks" to join his cabinet. "I've demonstrated-that it can be done in general and black people can do it in particular."

"It doesn' have to say that we're doing everything we should have done," he said. "But we've done enough good things, I think, to give people a feeling that we're in charge, we're on top of things, that we know what we're doing."

The high point of his first 100 days, Barry said, was standing in a boarded-up home in the 100 block of Bates Street, NW, and launching his program to take the boards off city-owned houses. "I could deliver in two and a half months on a major promise which ordinarily would have taken another mayor a year to do," Barry said. "And that was a major accomplishment.

"Bob Moore [the new D.C. housing director] came on the 20th of January and in less than a month and a half, with all the mess over there, we put together this program."

Much of the excitement about the new spirit Marion Barry has brought to city hall is in fact relief from the lack of spirit many saw in the 11 years of Walter E. Washington's administration.

"At this point," said Kenilworth Courts Housing Project tenant Michael Harrison, "I can say that he [Barry] at least makes a committed effort to talk about some things that Walter Washington tried to evade or tried to give the appearance of not being problems."

Minister Stanley recalled seeing housing Director Moore on television last week conceding that lax inspectors in his department were partially to blame for the fatal fire that killed nine patients at the group home that burned this week.

"That's different," Stanley said of the admission. "The Washington administration had been in so long that they were punch-drunk and defensive. That's new."

Much of the excitement about Barry stems from the realization, expressed by former Washington Urban League president John E. Jacob, that "Marion the wild man" is not "Marion the wild mayor."

This former dashiki-wearing militant now dresses in stylish three-piece suits. He rattles off the names of federal programs, terms himself a fiscal conservative, peppers his talk impressively with statistics and expresses concern for the problems of businessmen whom he at one time all but cursed.

Last week, for example, Barry appeared as a luncheon guest before the conservative American Enterprise Institute for Public Policy Research, a Washington think tank.

As the group of mostly white scholars and experts sat at the long conference table in chartreuse leather chairs, Barry graphically portrayed the problems of the city. He fielded questions aggressively, chuckled when the name of his hometown, Itta Bena, Miss., was mispronounced and addressed by their first names former Federal Reserve chairman Arthur F. Burns and Herbert Stein, chairman of the president's Council of Economic Advisers in the Nixon Administration.

The Barry magic worked on political anaylst Ben J. Wattenberg who said he was impressed. "I expected him to be a little more militant," Wattenberg said of Barry.

The mayoral Marion Barry is a well-cultivated creature, some friends of the mayor say, the product of a man who is aware that hints of his militant past could be red flags that hinder progress in his new efforts.

But Barry, the self-described "situationist." said last week that despite the image he once had as the personification of militant black anger in the District, he was seldom angry then and does not get angry that often now.

"Even in the 60s," barry said, "My anger was a matter of the times, a matter of style. It wasn't a matter of being angry just to be angry."

The major had to think a while and a silence fell over the room when a reporter prodded Barry on what things had made him angry in office.

"When somebody does some silly stuff that hurts a large number of people," he finally responded. "Like the fire.I mean that was uncalled for. I think. For human lives to be lost that way."

"I guess if I get angry at anything I get angry with the press more than I get angry with anybody else around here-including you," he said.

Barry said he thinks the press is holding him up to a standard that is five times higher than, for example, the executives of Prince George's and Montgomery counties and the governor of Maryland.

"I think the government is larger than Marion Barry, that things are going on far beyond me. I'd like to try to figure out how the press and others could begin to look at the good, the bad and the ugly in other parts of this government as opposed to staying on me all the time," he said.

"You're the mayor," the interviewer said.

"Of course, I'm the mayor, [But] I don't need and want all that puplicity."

Barry has always been a very private person, friends say. And the fact that the news media are now trying to intrude on his privacy is more crucial, because the private moments have become fewer.

Barry seldom jogs or plays tennis or shoots basketball, as he said he occasionally used to do. He doesn't get a chance to go to the theater, which about 18 months ago, he told a reporter. he had become fond of doing.

Other than bulky government documents, he gets to read little. The last book Barry read, he said, was "Let's Get Well," by nutritionist Adelle Davis.

Then there's the extra body weight and graying hair to suggest that this new job is really tough.

"My father was white [-haired] at 40, so I'm just half white, so I'm in good shape," he says.

"That's right. You're ahead of the game," he is told.

"That's right," the mayor agreed. "That would have happened to me anyway without this job.The job's not worrying me to death." CAPTION: Picture 1, Mayor Marion Barry in his office: "I guess the awesomeness of the job has settled into me." By James M. Thresher-The Washington Post; Picture 2, D.C. Mayor Marion Barry, left, holds staff meeting in his office with aides. They are, clockwise from top, Elijah Rogers, the city administrator; Ivanhoe Donaldson, general assistant to the mayor; Tina Smith, executive assistant to Donaldson, and Warren Graves, special assistant to the mayor. By James M. Thresher-The Washington Post; Picture 3, Mayor Marion Barry at work.