The most notable achievement of tonight's three-hour special, "Violence in America," on Channel 4 at 8 is that, for the most part, it shows us real violence, as against the gratuitous violence we see so often on our television screens.

NBC News and the special's executive producer. Stuart Schulberg, will no doubt be accused of pandering to what is a fairly evident appetite in this country.

But you cannot seek to spend three hours analyzing on television the causes and the effects of violence in this country without showing it, not as it exists in movies or on television itself, but as it really is.

"The fake, or gratuitous, violence is demonstrated in ample measure by quick cuts from movies such as "The Texas Chain Saw Massacre," "Bonnie and Clyde," and "Chinatown" plus scenes from television series such as "Serpico," "The Rockford Files," "Charlies' Angels," "Kojak" and "Delvechio," plus a moee VIOLENCE, B5, Col.1) (VIOLENCE, From B1)

Joseph Wambaugh, a former Los Angeles policeman who now writes best-selling novels and is the creator of the NBC series, "Police Story," understands the difference between wiolence as it is and violence on the TV or movie screen.

In the middle of the last hour of the special, which includes a look at movie violence and a remarkably honest and objective examination of violence on television, Wambaugh notes that television executives don't like to use the word "violence." They always talk about "action." Then he states: "We sanitize acts of violence."

Whatever television's sins, the juxtaposition of movies and television here make it quite clear that when it comes to panderng to America's basest taste, the movies are in a class by themselves.

But as Edwin Newman, who does a first-class job as the anchorman of this special, points out, violence as entertainment is a highly profitable business. To make certain that none of us misses his point, Newman adds: "You buy the tickets, you read the books, you see the movies, you turn the dials. You are the ones who are paying for it."

Perhaps the last hour, which examines our fascination with violence from the first pulp magazines through comic books and radio to television and movies, should have been the opening episode. In this way, we might better appreciate the stories and scenes of real violence that occupy the first two hours of the special.

But Schulberg obviously thought the show had to begin with what is calleiolence" - domestic and sexual violence which includes child abuse, wife beating, rape and the mass killer.

The second hour of the special examines the history of violence in America, the subculture of violence - poverty in the cities, racial segregation - and the climate of fear which has spread throughout the country, making growth industries of handguns and security devices.

Like most efforts to ecplore violence, this program raises a great many questions and does not provide very many satisfactory answers. Most galling was the response of Martine Barrat, a French documentary filmmaker who filmed youth gangs in New York for three years. When asked by Newman what should be done about these gangs, she said, "I think society should learn to love them."

Well, that's her opinion and she's entitled to it. But it is not going to reassure the millions of people in this country who are threatened or feel threatened - there may not be any difference - by the violence they see or imagine all around them.

That is why this special may make a signal contribution to what we think and feel about violence. It raises the issue, doesn't pretend that it has any easy answer or facile solution, and forces us to at least recognize the enormity and the complexity of the issue.

Newman was assisted in the reporting by Floyd Kalber, Carl Stokes and Linda Ellerbee. They all have done well by us, and they and the experts recognize that this is not a definitive look at the problem. It is more an exploration of a subject that we know, that we fear, but we little understand. It's a very rough three hours that will probably cause controversy. It should.