NEW YORK (AP) _ For CBS News, 1987 was the year of the layoffs, the year of the lowest- rated newscast, the year of the six minutes of black, the year of ''primal scream'' public relations.

''With all that, we ended the year saying 'Well, we came back,' '' says CBS anchor Dan Rather.

Indeed, what a difference a digit makes. CBS News is starting 1988 with a new morning news show, ''CBS This Morning,'' the return of the ''CBS Evening News'' to No. 1 in the ratings and the launching this Tuesday of ''48 Hours,'' a weekly documentary series inspired by the network's ''48 Hours on Crack Street.''

Rather admits ''1987 wasn't our best year. It ended, frankly, better than we thought.'' But he boasts now that ''CBS News has three prime-time, regular weekly hours of news programming - '60 Minutes,' 'West 57th' and now '48 Hours.'

''No other network has even two. I respect our competitors and I like them, but let's look at the facts.''

Last year, CBS News President Howard Stringer was at the center of the maelstrom when CBS management slashed millions from the CBS News budget and laid off more than 200 staffers, prompting a wave of editorials, including one by Rather, condemning the treatment of network news by bottom-line management. Rather publicly blamed CBS chief Laurence Tisch, who publicly blamed Stringer.

Stringer said that ''dealing with an organization that was, day to day, publicly exhibiting this primal scream was not the easiest thing in the world.''

The news division's morale was already low, having lost the ''CBS Morning News'' time period to an entertainment show, ''The Morning Program.''

''CBS Evening News'' fell to third place in the ratings during the summer.

In September, CBS Sports' live coverage of a tennis match ran overtime, cutting into ''Evening News'' time. Rather angrily left the set, and when the tennis match ended the network had to ''go to black'' for several minutes.

Rather continues to insist he walked off the set as a protest against what he saw as threatened ''trivialization'' of the news.

But with the new season, Rather's newscast returned to No. 1 in the ratings, where it has been for 16 straight weeks.

''The Morning Program'' was canceled for dismal ratings, and the news division regained the time period. The ratings of the new ''CBS This Morning'' are slowly improving.

''60 Minutes'' celebrated its 20th season by beating out ''The Cosby Show'' at the top of the ratings for a couple of weeks. The network stuck by its prime-time ''West 57th'' despite low ratings, and the show seems to be building an audience.

Now CBS is adding ''48 Hours'' in prime time, a sort of news-verite approach to documentaries.

''The emphasis (of ''48 Hours'') is on taking the viewer directly to the story, letting him or her experience it first-hand, relatively unfiltered by the journalist's perceptions,'' says ''48 Hours'' executive producer Andrew Heyward. ''The viewer sees the story as reporters do, as it actually unfolds and not after the fact when it's already been digested and neatly packaged.''

Rather will serve as anchor and often reporter, as he does on the first broadcast Tuesday, a look at Dallas' Parkland Hospital.

''We say this all the time,'' said Rather, ''we say, 'Listen, this is a terrific three-minute 'Evening News' piece,' and 'God, there's so much we have to leave out,' and 'I wish the viewer could have been there with me the full two days.' Voila 3/8 With '48 Hours,' that's what the beauty of it is.''

Heyward said a half dozen reporters and crews will actually shoot for 48 hours. Then the tape will be edited, with a minimum of narration.

Rather said he will be the reporter only when he can spend all 48 hours on the story. ''Andrew and I feel very strongly about not misleading the audience about what my involvement is or isn't,'' he said.

''My relationship is going to be total immersion,'' said Rather. ''As a reporter and a journalist that's the way I like to work, that's the only way I like to work.''

The three stories already shot are set at the hospital, the Denver airport and Miami.

''None of them yet are of the ideal topical breaking story,'' said Stringer. ''... When we hit it right and the audience is right there and we take you there, we'll be able to provide footage to other broadcasts,'' he said. ''We'll swamp the story with reporting talent.''