"Daddy, if you must see your white friends, please do so at your office and not at home," Percy Qoboza's 7-year-old son reportedly told him last year.

That was before Qoboza, 40, former editor of the now banned black newspaper, The World, was arrested by the South African government during its purge of political [WORD ILLEGIBLE] last October. Since then, his children have learned a painted political lesson, tending to confirm their anti-white feeling. Qoboza, generally regarded as a moderate, has been radicalized by his jailing, according to one report.

"They are very angry," said Qoboza's sister, Martha. "I fear they may grow up with a grudge against white people because of their father's detention.

"Doesn't Mr. Kruger have a family? What does he think about us when he sits down with them?" One child recently asked his mother, referring to Minister of Police and Justice Jimmy Kruger.

Qoboza is one of the 51 black political leaders put in "preventive detention" Oct. 19. On the same day, six white men whose political activity the government disapproved found themselves prisoners of a different sort when they were banned.

The recent flight to freedom-in-exile of newspaper editor Donald Woods, who was one of those banned, once again focuses attention on these who remain behind. Friends, relatives and attorneys report that frustation, bitterness, anger, boredom and uncertainty about the future plague the detainees.

For some, like Qoboza, who believed they were moderate enough to be tolerated by the government, the detentions came as a shock, and have changed them.

"Qoboza has lost faith in the ability of the progressive forces in the write community to effect change," said Richard Stemple, a political officer at the U.S. consulate in Johannesburg. Stemple, who has visited Qoboza as a personal friend on three occassions since his jailing, reports that he is generally in good spirits, but has been "radicalized by the experience.

Anne Qoboza says she sees a big change in her husband. For the first time," he is a bitter man" - not so much about his detention, but rather because of the banning of The World, she explained.

"It was the only voice for black people in this country and Percy lived for his work," she said.

The Post, formerly a Durban-based Indian newspaper, has moved into the vacuum left by the World but, well aware of the government't Oct. 19 message, it pulls its punches as a result, it has lost some of The World's readership and some of its best reporters.

Bitterness about the elimination of his life's work is something Qoboza shares with the younger, more radical detainees. Ramsy Ramakgopa and Aubrey Mokoena, both leaders of the black-consciousness movement started by Steve Biko, who died in police custody, are most bitter about the government's bannings of the organizations they worked for an the seizing of those groups' assets, including furniture, cars and cash. Their wives say they fear their husbands will emerge from prison more defiant than when they went in.

Also at Modderbee prison is Nthato Motlana, former chairman of the banned Soweto Committee of ten, and recognized as the preeminent political leader of that community of 1.5 million people. As a seasoned politician who has been detained before and who is "very strong-willed" according to acquaintances, Motlana is reportedly "coping" with this detention and treating it much as a "nuisance" that has to be endured for the time being.

While the government has isolated these political leaders from the people, it has not separated them from each other. The 47 male detainees are all at Modderbee, 27 miles southeast of Johannesburg. There they share four large, dormitory-like cells.

They can receive visits from their immediated family twice a week and from their attorneys at any time. Since their status is that of "prisoner awaiting trial," although none has been charged with a crime, reading material, television sets, radios and sports equipment are permitted.

The diverse political beliefs and age differences among the Modderbee detainees have created some friction, according to one onconfirmed report, with the younger black-consciousness radicals calling the more moderate, older men, "irrelevant."

The four women picked up Oct. 19 include Ellen Khuzwaye, the "grand old lady of Soweto," and Tenjiwe Mtintso, a close friend of Biko and a former journalist on Woods' newspaper. They are held at Johnnesburg's local jail.

Meanwhile, the whites banned on Oct. 19 live in prisons without walls. It's like being putting someone in a cage," said Illse Naude, wife of Beyers Naude, 62, former director of the banned Christian Institute.

"The worst thing is that he can't be involved, because he was always part and parcel of everything. Now if there are injustices he is not able to voice his concern and his disgust," she said.

This silencing has presented Naude with a spiritual conflict because he is torn between obeying God (by speaking out against injustices) and obeying the goverment's banning order.

Naude spends most of his time reading, answering correspondence and coping with the minute restrictions - like not seeing more than one person at a time - that go along with being banned! He obeys the rules so that none of his friends will be forced to lie if they are ever questioned by the police.

Another banned person, the Rev. Brian Brown, has continued to give sermons at his Johannesburg Methodist church, but he avoids political isues and does not greet his parishoners after the services in order not to contravane his banning order.

For most of the detainees, their future is a huge question mark. The length of their imprisonment depends solely on the determination by Kruger that law and order will not be upset by their release. Since many were employees of now banned organizations, they will have no jobs if they are released.

There is speculation that the government will let them out after next months elections for government-sponsored community councils in Soweto, which the detainees all had opposed as meaningless.

There is a strong feeling among families and observers that the most influential leaders, at least, will be banned if they are ever released.

Security police have already paid a visit to Anne Quoboza, asking such questions as what church her husband attends, which route he uses to go to work, which car he drives, and how many hours a week he works. Such information is needed to write "Banning orders," which are usually custom-made for each person. A banned person cannot write anything for publication and since Quoboza is a journalist, "that would kill him," his wife said.

These banned and detained men and women have received international attention because of the current interest in South Africa but they are not the first. The South African Institute of Race Relations estimates there are now close to 800 people in detention for political activity and 165 banned persons.