To help illustrate its special report, "1984 Revisited," CBS News had a computer devise a composite picture of how Big Brother might look, combining features from the faces of Stalin, Hitler, the Ayatollah Khomeini and other 20th-century tyrants. Watching the face take shape on the screen, a mischievous thought occurs: Wouldn't it be funny if it came out looking just like Walter Cronkite?

Of course, then they'd have to call him Big Uncle. As it turns out, the picture looks nothing like Cronkite, who anchors the report, at 8 tonight on Channel 9. Although it is noted that George Orwell picked the year 1984 rather arbitrarily as the time-setting for his nightmare novel of a totalitarian world (he also considered calling his book "1948"), the real 1984 is, in fact, mere months away, and Cronkite and company endeavor to determine whether Orwell's dire foretellings were farfetched or near-fetched.

The conclusion reached by the program appears to be, nearer than farrer.

"How close are we?" Cronkite asks ominously. "How close? How close?" Then he vanishes ghost-like from view. On this show, they don't fade to black, they fade to white. Maybe they think it's more 1984ish.

The hour is engrossing, instructive and inventively produced (by Jonathan Ward), but the writing is occasionally on the radio-hokey side and--perhaps this is unfair, considering the frequency with which CBS News finds itself a litigious target these days--there's the nagging impression that the show was produced according to the directive, "Give us something that couldn't in a million years cause us any trouble." It happens that the executive producer is Burton Benjamin, previously a CBS News administrator and the author of the in-house report on the hot-potato "CBS Reports," "The Uncounted Enemy: A Vietnam Deception."

All that aside, Cronkite is, on this broadcast, pretty wonderful. He's the perfect correspondent to tell us of encroaching dooms in portentous tones. The program offers portentousness aplenty as it surveys ways the modern world resembles the regimented, repressive society envisioned by Orwell in his cautionary prophecy. A segment of the program offers a discussion of Orwell by some, including Malcolm Muggeridge, who knew him. It's irrelevant, actually, but diverting.

Among the niftier graphic devices employed, in addition to the computerized composite mug shot, and some not-very-nifty drawings illustrating the plot of the book, is a map on which Cronkite points out the existing nations of the world that can be classified as truly free societies, like for instance the United States. As Cronkite notes, there are very few others. They make barely a peep in the global arena.

Orwell couldn't have known how much technology would facilitate the social horrors he envisioned. He never stood like an accused criminal at a department store while a clerk telephoned a computer to find out if he were trustworthy or had some hideous smirch on his credit character. Cronkite gets into the weightier sides of this. He visits the offices of the Encyclopedia Britannica to find out how easily history can be written. Just a few well-placed keys on a computer terminal keyboard and, de-voila .

The Russians rewrite history all the time, Cronkite says. Comrades become nonpersons in the Soviet Union simply by being airbrushed out of group photographs in which they once appeared. Soviet Police Chief Lavrenti Beria made an edition of the Russian encylcopedia, Cronkite is told, but then became a nonperson. So purchasers of the books were sent a letter urging them to remove the Beria pages and replace them with new pages on the Bering Sea. And it was bye-bye Beria just like that.

But one needn't go to Russia to find 1984 alive and well in 1983. "A world without privacy," much as Orwell saw it, could well be the end result of what Cronkite calls "the rise of the computer state" now taking place. Networks of computers keep track of American citizens and their comings and goings through the passport office, the census bureau, credit card companies, banks, the Social Security system and the ultra-Big-Brotherly IRS. It hardly takes galloping paranoia to foresee a day when all these computer networks will interlock into one all-knowing information monster, enough of a threat to make the movie "Wargames" look like child's play.

Cronkite says the federal government now has "15 to 20 active files on every person in America."

The program also takes cursory looks at behavior modification experiments and such potential tools of the state as two-way cable TV, only in limited use now but conceivably a convenient device for invading the privacy of the American home. You watch television; television watches you. The increased use of surveillance cameras is also noted. "Honey, I'm Big Sister," laughs a woman cop at a bank of TV monitors in Miami.

Near the hour's end, Cronkite offers a plausible worst-case scenario "that might bring 1984 closer even in our most durable democracy," a domino theory that is as good, or bad, as any other, and then he concludes with a warning from Orwell: "Something like 1984 could happen. The moral to be drawn from this dangerous, nightmare situation is a simple one: Don't let it happen. It depends on you."

When Walter Cronkite warns you, you stay warned. Come January 1st, the phrase "happy new year" is going to take on a slightly twisted meaning. "1984 Revisited" convincingly maintains that it isn't too early to become very, very nervous.