Interview :David Letterman He's No Johnny Carson

When his late-night show debuted on NBC in 1982, David Letterman was a young stand-up comic known mainly for occasional stints as a Tonight show guest host. Now, as his own show prepares to celebrate its seventh anniversary, Letterman has established himself as the medium's most inventive * and influential comic. Like Saturday Night Live in the '70s, Late Night with David Letterman has defined the cutting edge of TV comedy in the '80s: hip, irreverent, self-parodying, both scornful of and fascinated by the cliches of show business. Sitting in his Rockefeller Center office recently after a late- afternoon taping of...