A few weeks ago, at a gathering of Soviet cultural workers here, a theater director received a huge ovation for wishing everyone in the hall a happy New Year -- "the full-of-promises year of 1983."

The roar of approval from that audience of intellectuate reflected a feeling of expectation and hope that has been palpable in the Moscow air since the change of leadership in the Kremlin last November. In his first 100 days in office, Yuri Andropov, the new leader of the Soviet Communist Party, has moved swiftly to push this lumbering behemoth of a country in a new direction. His surprisingly bold leadership has fueled widespread expectations of new departures still to come.

The new mood is an abrupt change from the immobility and public apathy of Leonid I. Brezhnev's last months. To keep it alive Andropov must make good on at least some of the hopes he has helped to stir, and there is no guarantee that he can do so. But he has already broken the mold of previous transitions to new leadership, taking command more forecfully and more quickly than any of his predecessors, from Stalin (the first successor, after Lenin's death) to Brezhnev.

If there is one theme that has emerged during his first 100 days with clarity, it is Andropov's insistence on social and economic discipline. Lacking economic tools, he has resorted to police methods not seen since the days of Stalin when he sent countless deputized vigilantes and police to carry out daytime raids throughout the country to fight worker absenteeism.

The raids lasted for three weeks and were presumably designed to shock the nation out of its lethargy. Recent government statistics show that in January, industrial output and labor productivity both experienced dramatic increases.

At the same time Andropov has conducted an extensive purge of the governmental and party bureaucracies. Perhaps the most significant single act was the abolition of the secretariat of the general secretary, Moscow's equivalent of the Whie House staff. Under Brezhnev, the secretariat had grown in size and authority to become the effective power center in the country. Its various counselors and assistants could overrule their counterparts in the government and the party by virtue of the leader's authority.

The purge of the government thus far involves scores of ministers and department heads.

Perhaps the most significant appointments include the naming of Gaidar Aliev, a veteran KGB operative whom Andropov appointed to full Politburo membership, as the first deputy prime minister, and of Vitaly Fedorchuk, another KGB veteran, as interior minister to replace Gen. v. Shcholokov.

The prominence of KGB men in top positions produced an instant joke in Moscow playing on the acronym for the voluntary Society in Support of the Army, Airforce and the Fleet, DOSAF. It is now jokingly referred to as the Society for the Support of Andropov, Aliev and Fedorchuk.

It is clear that Andropov is putting into key government positions tough and efficient men, and that in this way he hopes to make the governmental mechanism responsive to his demands.

Among those who were ousted are Transportation Minister Ivan Pavlovski, 60; Minister of Agricultural Construction S. H. Khitrov, 72; Trade Minister A. I. Struyev, 77; Deputy Premier V. N. Makeyev, 52; chief of the Young Communist League Boris Pastuhov; head of the central committee propaganda department Evgeny Tyazhelnikov, 52, who was in effect the country's propaganda minister; sports chief Sergei Pavlov; editor-in-chief of the government newspaper Izvestia N. A. Alexeyev, and many lesser officials.

In virtually all instances, Andropov sought to ease these retirements by giving them an honorable appearance, or by shifting people to responsible if lesser positions. Trapeznikov, for instance, is now ambassador to Romania.

For the first time since Lenin, the Soviet media is now publishing accounts of weekly Politburo sessions. For the first time since Khrushchev, a Soviet leader has gone unannounced to a factory to speak directly to workers about their problems.

In a country with a vertical structure of authority, the leader's style has a rippling effect. People are now coming to work on time because the leader does so. Soviet journalists, for example, tell a story about the editor-in-chief of the main Soviet weekly paper who used to conduct his business by phone from his dacha. Nowadays, the editor is working each day at his office.

None of Andropov's actions thus far is revolutionary; in Western terms the changes he has made are modest. But Andropov is a Soviet, not a Western, leader, and measured against Soviet experience, his performance in these first 100 days has been extraordinary. It took Stalin, Khrushchev and Brezhnev literally years to establish a position as strong as the one Andropov seems to have won for himself in three months.

When the leader of the Soviet Communist Party dies or is removed from office, a new leader is quickly selected. But the new leader inherits only the position, not the authority and prestige of his predecessor. He also gets his predecessor's agenda of unsolved problems, and his predecessor's key personnel.

No automatic resignations are submitted to the new leader by Politburo members, cabinet ministers, ambassadors or other high officials. None of them, indeed, is permitted to resign, according to an entrenched if unwritten rule.

It is one of the important myths of the Soviet party that it does not make mistakes -- that it selects the very best people to fill leading positions, and that consequently there is no reason for a wholesale purge of officials, even when many old-timers are known to be seriously ill or incompetent.

A new leader is not free to announce a new national agenda by himself. Nor can he decide unilaterally to bring new blood into the hardened arteries of the party bureaucracy. He must first consolidate his authority within the existing power structure if he is ever going to institute changes that would leave a personal imprint on the country.

At 68, Andropov inherited the leadership of a country in crisis. At home, after a decade of growth, the economy was on a severe decline. Soviet agriculture was simply not able to feed the country.

Abroad, Moscow was bogged down in Afghanistan and threatened in Poland. Detente, the cornerstone of Brezhnev's foreign policy through which he sought to raise domestic living standards by regulating relations with the West, was in tatters. The planned deployment of new U.S. nuclear missiles in Western Europe confronted the Kremlin with a major threat and a major challenge.

That Andropov could establish himself so quickly as the Kremlin's preeminent leader is to some extent due to his personal qualities. His earlier career as ambassador to Hungary, secretary of the central committee and particularly his 15 years running the KGB security apparatus have endowed him with a variety of skills and assets to help him steer through the Byzantine thickets of Soviet politics.

The KGB job also turned him into one of the best-informed Soviet officials on foreign and domestic matters, which helped him hit the ground running the moment he was elected general secretary.

Because of his experience, Andropov was pushed to the top by the armed forces chiefs and the KGB, the two most powerful Kremlin lobbies. That this took place at a moment of crisis is particularly significant. President Reagan's rearmament program was seen as a profound and threatening challenge to the security of the Soviet Union and the Soviet system itself. It required a determined response by a tough and determined new leadership.

There are Western and Soviet observers here who argue that Andropov has yet to secure full control over the course of political developments in Moscow and that he may yet prove to be a transitional figure. Nobody questions the proposition that he has established his preeminence in the leadership. Yet some experts believe there is a silent Brezhnevite majority in the politburo which is rhetorically supporting the new leader but is really waiting for him to falter.

Adherents to this view note that Andropov has not removed his rivals in the Politburo and established his own majority. Some suggest it is evidence of Andropov's weakness that the post of president, a largely ceremonial job, has been left empty.

It seems more likely, though, that Andropov has fully consolidated his authority and is moving gradually in a direction of his choice. The important point about the presidency may be that no one else has taken the job. Andropov's priorities suggest that the interests of his principal constituencies are uppermost in his mind. This in turn means that domestic issues -- and particularly efforts to revitalize the economy -- will remain his primary concern.

Not that Andropov has ignored foreign policy. He has focused on Moscow's relations with the United States and China, following the basic policy line laid by Brezhnev.

With respect to the United States, the main Soviet concern at the moment is the planned deployment of new American medium-range nuclear missiles in Western Europe. The Soviets try to convey the impression that they take this deployment as seriously as the Kennedy administration took the deployment of Soviet missiles in Cuba in 1962.

The Soviets are using their best propaganda resources in efforts to prevent the U.S. deployment. The outcome of the Geneva, medium-range talks could to a large extent shape Soviet-American relations for the next two decades.

It is in this security context that domestic affairs gain the overwhelming importance in Andropov's mind. When he bluntly told the workers that greater productivity and output are the basis of Soviet security, he was reflecting the view of the armed forces chiefs who have openly stated their anxieties about economic difficulties during the past two years of Brezhnev's life.

Despite his long career in the security police, the popular preception of Andropov is a curious one. He is respected rather than feared. His anticorruption drive is popular and so is his insistence on law and order. There is a feeling among Soviets that he is attempting to make the government and party at least appear more accountable to the people. His speeches, which are short and to the point, are appreciated. So is the fact that he is not making exaggerated promises.

Andropov's straightforwardness is refreshing for the population. In his first major speech he conceded that he had no "recipe" for curing the country's economic ills. He also bluntly told the workers that they should not expect "miracles" from the government, a rather startling reversal for pronouncements from Soviet leaders, who traditionally have insisted that the government would take care of everything for the people.

Popular jokes provide an insight into public attitude toward the new leader. The Kremlin is now jokingly called "Andropolis." The study of Soviet politics is referred to as "Andropology." Wags say a new pill invented to clear up huge governmental headaches was to clear up huge governmental headaches was named "Andropil." And it is said that Andropov, like Lenin, has introduced his own NEP, an acronym for new economic policy. Andropov's NEP (in Russian) stands for "introduction of basic order."

The leader's personal habits also seem to have left an imprint at least on this capital. Andropov can be seen going to work each day at 8:40 a.m., and he can be seen going home no earlier than 6 p.m., and often after 7.

An ascetic man, he is said to drive himself and his immediate subordinates hard and has made known his distaste for wasting time. Solid work, rather than patriotic exhortation and speeches, is the way to solve economic problems, he said in a speech. The only time he spoke directly to the workers was during their break.

It seems noteworthy that all recent party conferences and consultations have taken place on Saturdays and Sundays -- not during working hours as in the past.

It is said here that the change in style will eventually bring about a change in the substance of Soviet policies. So far, there are only hints to that effect.

The tone of the public debate has become more critical and open. Various proposals are aired in the media for providing meaningful incentives to farmers to increase agricultural output. The government has raised prices on a variety of items in what could be a prelude to some adjustments in this centrally planned economy. There have been new decrees to tighten economic discipline accompanied by criticism of uravnilovka, the practice of paying all workers the same salaries regardless of individual performance.

At the same time, the new leadership appears inclined to act more decisvely even than Brezhnev did to stamp out any form of organized dissent. It has sharply reduced the emigration from the Soviet Union of Jews, ethnic Germans and Armenians, so that only a handful are now getting permission to leave.

Intellectuals are hoping for some liberalization in the realm of culture, but it is too soon to say whether those hopes are justified. The signals are mixed. While the authorities have recently shut down some controversial theaterical performances, they have shown signs of unusual tolerance toward former politicians who have become non-persons, including Khrushchev.

One has the impression, however, that such matters are of marginal importance to the new leadership. Under Andropov, the inner circle of leaders consists of Defense Minister Dmitri Ustinov, Foreign Minister Andrei Gromyko, Aliev and Vladimir Shcherbitsky, the Ukranian party chief.

These aren't the sort of men who seem likely to spend much time worrying about what plays can be staged in Moscow's theaters. They seem preoccupied with the American challenge and the overriding need to get the Soviet Union moving again. They are serious men with serious purposes. It will take more than a hundred days to gauge their real progress.