A year after the military coup that ousted Isabel Peron, President Jorge Rafael Videla of Argentina is firmly in saddle, thanks to domestic gains and President Carter.

The economy which was foundering under Peron, is on the mend and leftist terrorism is greatly reduced. Kidnapings and violence committed by rightist extremists seem also to be fading somewhat following private exhortations from Videla to his troops and a delicate balancing and shuffing act among the "hard" and "soft" groupings of generals.

Divisions among the officers wer papered over in a roar of nationalistic indignation when Carter propsoed a halving of Argentina's military aid because of human-rights violations.

"Carter made a great mistake in putting all the generals together in one sack an accusing all of them," said a prominent former political figure. "Everyone has to back Videla now but we don't know what that's going to cost him in the long run."

Argentina promptly rejected the remaining $15 million in U.S. aid, and was followed in aid refusals by Uruguay, Brazil, Chile, El Salvador and Nicaragua. Analusts of U.S. Latin relations are still sorting our the balaces between official protests and the rights abuses and disappearances, and whoops of joy from groups in clandestine opposition to the dictatorships.

In Argentina, however, the need to stand up to the United States with a united front has apparently helped to consolidate Videla's position as first among equals in the three-man ruling junta. What he may have had to concede, if anything to win that backing is the subject of much speculation. There is however no further talk of replacing him as president.

In his first year, Videla has maintained the slow and stubbornly cautious pattern of decisionmaking that preceded the coup last March 24. The style still irritates his critics, among them the many members of the junta, Adm. Imilio Massera. Videla defended the nations progress in a conversation with local journalists: "The baby moves little, four or five steps a day, but he doesn't lose any ground."

In this vein, the officers promised Economy Minister Jose Marthinez de Hoz a year's free hand at restoring the shattered national accounts, and they have backed him firmly against criticism from both left and right that improvement was not coming fast enough. Videla has resisted pressure to crack down faster on truculent generals, with the result that he has converted many of them.

He has moved equally slowly, critics charge, against continuing human-the net reslut has been that nearly everyone has something to complain about.

Nevertheless, Videla and the other officers have keep open their lines of communication the country's various political elements, even though all political and union activities are officially suspended and many leaders are in jail. Everyone agrees that the soldiers know what the problems are "Each one has his own little storefront listening post" the former political figure said. "The time is coming quickly when they will have to act on what they know."

Like most of the country, the politician is waiting engerly for Videla's speech March 29, the anniversary of his assumption to the presidency.

The degree of improvement in Argentina is relative. Writs of habeas corpus is relative. Writs of haveas corpus continue to be rejected by the hundred in the courts and a daily line of relatives of missing person forms outside the government Pink House, waiting to ask officials for news.

The Permanent Assembly for Human Rights, an ecumenical organization of churchmen and public figures, yesterday formally asked Videla to make public a list of political prisoners as "the only way of dissipating the anguish and prolonged agony of thousands of families ignorant of the location of their loved ones." Church sources estimate that there are about 5,200 prisoners, but other guesses are much higher.

The respected daily La Opinion estimated that leftist terrorists lost 4,000 persons in 1976 through deaths, wounds, arrests or desertions. The days of head-on confrontations between guerrillas groups and authorities are over, although the terrorists claim their silent supporters are more numerous then ever. For every bombing or attempt on Videla's life - there have been three close calls so far - there is an apparent act of retribution by the right.

Army sources call those acts the work of "freelancers" and sy they expect the violence will be over in about six months. But incidents continue.

Friends of 20 Uruguayan refugees arrested in Argentina in June and July supplied journalists and church elements with documentation of what they said was the transfer of those arrested to Urugnay by Argentine police. Such a transfer violates international rules on treatment of political reguees.

The government denies any knowledge of the whereabouts of union leader Oscar Smith, and neither the right nor the left has claimed his kidnaping last month.

Unions, which formed the bedrock of support of Isabel Peron and her late husband, Juan, are about to be granted organizational rights but only up to the regional level. The government want's to prevent the formation of another nationally powerful General Labor Confederation like the one they blame for much of the economic troubles under peronism.

The economic chaos has abated, but the measures used have fallen hardest on the low- and middle-income sectors.

Inflation, which might have reached 5,000 per cent for 1976 had it continued at pre-coup levels, has slowed to around 10 per cent per month, according to official figures. Employment continues more or less full with 4 to 6 per cent jobless, depending on the source. "Now we have 4 per cent unemployed and 96 per cent working for starvation wages, and 100 per cent of them are unhappy," said a high military leader.