Johannesburg — As a white person drove through the dusty streets of one of South Africa's troubled black townships recently, a black teen-ager picked up a rock and held it menacingly before letting it drop back to the ground.
The end of the year finds South Africa relatively quiet. But it is more an uneasy silence brought on by government force than a genuine calm.
Violence erupted in more than a score of black townships this year, leaving approximately 160 dead and millions of dollars' worth of property damage. It is regarded as the worst year of black unrest in South Africa's history, surpassing (though the death toll remains lower) the Soweto disturbances of 1976.
Despite the trauma of 1984, the government appears dedicated to continuing its gradualist approach of ''reform,'' discredited though it is among most blacks. There are signs the government plans either to amend or repeal several segregationist laws next year that prohibit marriage or sex across the color line and that prohibit integrated political parties.
There are two broad perceptions of the internal turmoil South Africa has faced this year. The divergence of those perceptions suggests this country faces greater internal conflict in 1985 and beyond.
One perception is held by the government and most of the country's whites. It is that the country is in the middle of a process of slow but genuine reform of its policy of racial segregation, called apartheid. They expect that process to be turbulent as radical elements seek to undermine evolutionary change.
The other perception, held by most blacks is that ''reform'' means nothing more than ''reformulated apartheid'' and that the government is not yet addressing the real questions, let alone finding solutions. These blacks believe this year's upheaval is yet another sign that South Africa is heading toward greater internal conflict. And the government will be required to rule through increasing force and repression, they say.
Black attitudes and the atmosphere in the townships changed markedly in 1984. A year ago a white was greeted in black communities mostly with curiosity. Now there is suspicion and anger - and an inclination to violence.
''There is a more fatalistic approach'' among blacks, says one respected black community leader, ''a feeling that crisis is the order of the day.''
This year's upheaval was accompanied by significant political developments, analysts say, that seem to have shifted a little more power and a lot more confidence to the government's black opponents. Black political movements were revitalized in 1984 and, unless banned by the state, seem poised for further gains. The government's policy of so-called reform provided a rallying point for opposition groups like the United Democratic Front (following in the tradition of the banned African National Congress) and the National Forum (carrying on the philosophy of the Black Consciousness movement, which emphasizes that blacks must liberate themselves without help from whites).
Black trade unions made their most serious advances to date into the political realm with a two-day strike in November that showed black workers' willingness to challenge the government on some issues. Black labor's tentative move into politics is backed by the growing strength of the union movement, now making itself felt in the nation's crucial mining industry.
The South African government has taken on a new, less racially exclusive look while keeping power in the hands of whites. Pieter Botha consolidated more political control in his own hands under a new Constitution that made him president instead of prime minister. Coloreds (persons of mixed-race descent) and Indians were brought into Parliament. Blacks were left out.
Instituting the new Parliament shuffled the deck of white politics, causing some of Mr. Botha's right-wing Afrikaner supporters to defect, but enlisting new supporters from the less-conservative English community. The new Parliament sowed serious dissent among Coloreds and Indians, most of whom refused to support it in August elections.
The only united reaction to the new Parliament came from the country's black majority, which warned it was a dangerous step likely to promote violence.
There appear to be three basic causes for this year's unrest:
* Economic decline. South Africa has experienced its most serious economic downturn in modern times for the past three years. Blacks bear the brunt. They are losing their jobs, and paying higher prices and taxes. Many in the rural areas are going hungry. Yet they have no say in government. Drought has also forced South Africa, traditionally a large food exporter, to import maize (corn) for the second year in a row, taking a heavy toll on its foreign-exchange earnings.
* Constitutional exclusion. South Africa's new Constitution excluded blacks. Blacks saw this as no accident or oversight but a culmination of the policy of apartheid which holds as one of its tenets that blacks belong in ethnic ''homelands'' and have no right to political participation in the central government of South Africa.
* Educational frustration. Blacks value education as a means to rise above their inferior status in South Africa. But they perceive their segregated, inferior schools as tools by which the government seeks to keep them down.
This year's events have shown that the urban black youth of South Africa are highly politicized.
Black unrest in 1984 began brewing in the high schools of Atteridgeville, an older black township west of Pretoria. Students arrested in late 1983 were not readmitted in 1984. Fellow black students boycotted classes in sympathy.
Eventually, six secondary schools in Atteridgeville were closed for most of the school year. But the issues in that community crystalized and gained wider support among black students at many other schools throughout the country. Students demanded an end to the age limits for each school grade (used in Atteridgeville to keep students arrested one year from repeating that grade the next year), stricter controls on teachers (charged with using excessive corporal punishment and having sexual relations with students), and most important, the establishment of ''student representative councils.''
The government eventually agreed to establish student councils in 1985. But blacks rejected the form of the councils envisaged by the government. Negotiations about their structure continue.
As student boycotts spread at midyear, another warning flare was fired on the economic front. The small rural township of Tumahole, 65 miles south of Johannesburg, erupted in riots that lasted almost a week. The protests were over higher rents and the hike of the sales tax in South Africa to 10 percent.
Against this backdrop of simmering protests over education and economic hardship, the government moved briskly with its new Constitution.
The August elections for Coloreds and Indians flopped, with only about 30 percent and 20 percent of their respective registered voters going to the polls amid violent confrontations between police and those urging people not to vote.
Although many of the people campaigning for a boycott of the elections were locked up by the government, opposition forces were emboldened by their success at the polls.
On Sept. 3, the same day South Africa's new Constitution came into being, several black townships south of Johannesburg erupted on a scale that shocked the country. Rioting swept the townships and left some 30 dead.
Observers were stunned at the ferocity of the violence, and particularly the way angry blacks attacked local black officials, who were apparently seen as traitors for their participation in official institutions created by the white government.
The government reacted with an unprecedented show of force. It used the Army to quell dissent in the black townships. Previously it had been a police responsibility, and many feel the use of the Army is a watershed for South Africa.
Black unrest took a correspondingly significant turn. Black unions, only legally recognized in South Africa since 1979, joined forces with students and community groups in calling for a general strike in Transvaal Province Nov. 5-6.
The strike was devastatingly effective, slowing the economy, boosting blacks' confidence, and alarming the government. Following the strike, the government detained key union leaders and other blacks responsible for the strike.
The government has dropped all its orders for ''preventive detention'' of black political and labor leaders. But many of those government opponents have been charged with treason.
There are signs that Pretoria may go further with its ''reforms'' in 1985, conceivably dropping its ban on marriage or sex across the color line and its prohibition of integrated political parties.
But black demands now focus on political participation and most analysts do not expect changes in the race laws to placate blacks.