This guide is designed to alert readers to the scope and variety of programming coming up. Listing is not meant to represent blanket endorsement. Readers are urged to be selective. FRIDAY Free Show Tonight (PBS, 10-11 p.m.): Repeat of colorful music and comedy revue, narrated by Roy Acuff, about show business greats who started their careers riding medicine show wagons. SATURDAY
US Open Golf Championship (ABC, 2-6:30 p.m., EDT): Fourth round of the tournament from Southampton, N.Y., with Jack Nicklaus in his debut role as special commentator.
The Science of Beauty (PBS, 7-8 p.m.): Exploration of the ``science'' of skin care. SUNDAY
Newsleaders (PBS, 7-7:30 p.m.): Series of informal conversations with outstanding journalists, editors and publishers, hosted by John Chancellor. Katharine Graham of the Washington Post/Newsweek sits for a detailed interview.
Visible Target (PBS, 10-10:30 p.m.): The drama and sorrow of the Japanese-American evacuation of Bainbridge Island, Wash.
Japan's Grand Kabuki in America (PBS, 10:30-11 p.m.): The history, tradition, and technique of Japan's ``total theater'' as it tours America. Hosted by Dick Cavett. MONDAY
Empire of the Hittites (PBS, 8-9 p.m.): ``In Search of the Trojan War'' reconstructs the diplomatic crises that may have encompassed the Trojan War. Host Michael Wood traces a journey to the Aegean coast for a confrontation between the emperor of the Hittites and the Great King of Greece.
Sunday in the Park with George (PBS, 9-11:30 p.m.): ``American Playhouse'' presents this Pulitzer Prize-winning musical, with music and lyrics by Stephen Sondheim. Bernadette Peters and Mandy Patinkin re-create their former Broadway roles in what could be the best television musical in years. TUESDAY
The Assault on Affirmative Action (PBS, 9-10 p.m.): ``Frontline'' travels to Indianapolis and Memphis to examine the achievements and failures of affirmative-action policies over the past 20 years.
Nicaragua was our Home (PBS, 10-11 p.m.): This program investigates the tragic plight of the Miskito Indians of Eastern Nicaragua, linked to ``mistakes'' committed by the Sandinistas. WEDNESDAY
Mark Russell Comedy Special (PBS, 8-9:30 p.m.): In a live performance, TV's only political satirist pokes irreverent fun at the day's news.
Winston Churchill (PBS, 6:30-10 p.m.): Dramatic one-man show by Robert Hardy depicts the courage and wit of Britain's great wartime leader.
Normandy to Berlin: A War Remembered (PBS, 10-11 p.m.): Repeat of last year's extraordinary photo commemoration of the 40th anniversary of V-E Day.
Please check local listings for all PBS programs since local station's option often results in differing schedules.