HOLLYWOOD, Calif., Jan. 21--Cecil B. De Mille died of a heart ailment today in his home on De Mille Drive here. He was 77 years old. At his bedside when he died were a daughter, Cecilia, and her husband, Joseph Harper. Mrs. De Mille, who is 85 and has been ailing for several years, was not informed until later in the morning. They had been married for fifty-six years. Although confined to his home since last Saturday, Mr. De Mille continued to work. He was preparing to start filming "On My Honor," a history of the Boy Scout movement and its founder, the late Lord Baden-Powell. More than 1,000 messages of condolence from persons in all walks of life had been received by late afternoon at the Hollywood office of Western Union. In addition to their own daughter Cecilia, Mr. and Mrs. De Mille adopted three children. They are Mrs. Katherine Quinn, a former actress and wife of Anthony Quinn; Richard De Mille, who is studying for a doctorate in psychiatry at the University of Southern California, and John De Mille, who is in the real estate business here. Also surviving are thirteen grandchildren and two great- grandchildren. A funeral service will be conducted Friday at 11 A.M. by the Rev. Harry E. Owings Jr., rector, in St. Stephen's Protestant Episcopal Church in Hollywood. Cecil Blount De Mille was the Phineas T. Barnum of the movies--a showman extraordinary. A pioneer in the industry, he used the broad medium of the screen to interpret in "colossal" and "stupendous" spectacles the story of the Bible, the splendor that was Egypt, the glory that was Rome. He dreamed in terms of millions, marble pillars, golden bathtubs and mass drama; spent enormous sums to produce the rich effects for which he became famous. During his lifetime, Mr. De Mille produced more than seventy major films, noted for their weight and mass rather than for subtlety or finely shaded artistry. In 1953 he won an Academy Award for "The Greatest Show on Earth," which had been released a year earlier. Previously he had won neither an Oscar nor the New York Film Critics annual award. Since then, however, he had been showered with honors, including: The Milestone Award of the Screen Producers Guild, the Great Living Americans Award of the United States Chamber of Commerce, the Fame Award of Achievement of the motion picture industry and the Washington Pilgrimage Award of the Religious Heritage of America, Inc. Mr. De Mille also received citations from the Salvation Army and, for ten consecutive years, was voted the industry's top producer-director by the Motion Picture Exhibitors. France conferred upon him the honor of Knight of the Legion of Honor, the Netherlands inducted him into the Order of Orange Nassau and Thailand conferred on him the Most Exalted Order of the White Elephant. The fact that his first Oscar did not come until forty years after he had produced one of the earliest four-reel feature films, "The Squaw Man," was brushed off with a characteristic De Millean gesture: "I win my awards at the box office." This was true. His pageants and colossals awed the urban, suburban and backwoods audiences. By 1946 his personal fortune, despite his regal spending habits, was estimated at $8,000,000. The producer basked in publicity's intense glare in late 1944-45 when he made a heroic issue of a demand by the union of which he was a member that he pay a $1 contribution to its political action fund. He had been in radio about a decade by that time, staging shows for a soap company at a reported salary of $5,000 a week. Mr. De Mille carried the fee fight to the courts, was defeated, and then went on a one-man campaign against political assessments by unions. He later sought reinstatement in the union, but failed to get it. Mr. De Mille was born at De Mille Corners, a backwoods crossroads in Ashfield, Mass., on Aug. 12, 1881, while his parents were touring New England with a stock company. His father, Henry Churchill De Mille, was of French-Dutch ancestry; his mother, the former Matilda Beatrice Samuel, of English stock. At 17 he went on the stage. He played in "Lord Chumley," "The Warrens of Virginia" (which he adapted to the screen later), "The Prince Chap" and "Hearts Are Trumps." In the cast of "Hearts Are Trumps," was Constance Adams, daughter of a New Jersey judge, engaged in a small part. They were married Aug. 16, 1902, four days after Mr. De Mille's twenty- first birthday. In 1908 he was having lunch with Jesse Lasky when the talk turned to movies. Mr. De Mille threw in his lot with the ambitious Lasky and with a newcomer in the theatre, Sam Goldwyn. All three reached the top run in the movie world, though finally along separate paths. The first product of the new movie company--The Jesse L. Lasky Feature Play Company--was a screen version of "The Squaw Man." It was turned out in an abandoned stable in Los Angeles with crude equipment, but it bore Mr. De Mille's mark. He was credited with many motion picture innovations. Indoor lighting was first tried out on an actor in "The Squaw Man." This picture, besides being the screen's first epic, was also the first to publicize the names of its stars. On his first day as head of the Lasky-Goldwyn-De Mille combine, Mr. De Mille signed three unknowns--a $5 cowpoke named Hal Roach, an oil-field hand named Bill (Hopalong Cassidy) Boyd and a thin-nosed teenager who called herself Gloria Swanson. This was the nucleus around which he built his galaxy of screen stars. To Mr. De Mille was attributed the inspiration for doing different versions of a popular picture, a possibility everyone else had overlooked. He is also supposed to have conceived of opening films with a printed cast of characters. The so-called "sneak preview"--showing a film to a test audience-- was another contribution. The first "Ten Commandments," produced in 1923 at a cost of $1,400,000, made money. From that time on Mr. De Mille wallowed in extravagant props and super-gorgeous sets. It was a good formula. It worked in "The Crusades," "The Sign of the Cross," "King of Kings," "Cleopatra" and a long list of other De Mille spectaculars. In the latter part of his career Mr. De Mille switched from Scriptural subjects to the American scene. He turned out flamboyant chunks of Americana in "The Plainsman," taken from the lives of Wild Bill Hickok and Buffalo Bill; "The Buccaneer," a dramatic account of the life of the pirate Jean Lafitte; "Union Pacific," and "Reap the Wild Wind," a story about Key West. "The Buccaneer," originally produced in 1937, was remade last year, with Mr. De Mille acting in a supervisory role. Unlike the new "The Ten Commandments," "The Buccaneer" was what the trade called a "remake." "The Ten Commandments," however, was a completely new version of the Bible story and differed greatly from his first film of that title. "The Ten Commandments," issued in 1956, had grossed a reported $60,000,000 here and abroad by last fall. Other expensive pictures Mr. De Mille produced were "Unconquered," in 1947, and "The Greatest Show on Earth," which cost an estimated total of $4,000,000 each. In 1949 he produced "Samson and Delilah" for about $3,000,000. During that same year he was named chairman of the Motion Picture Industry Council. Mr. De Mille, who gave the University of Southern California a theatre in memory of his parents, was lavish with gifts to other institutions. In June, 1958, he learned that plans to place translations of the hieroglyphics on the Egyptian obelisk in Central Park were being put aside for lack of funds. He offered to pay the cost of erecting four bronze plaques at the base of "Cleopatra's Needle," saying: "As a boy, I used to look upon the hieroglyphics as so many wonderful pictures." Two weeks ago, the Department of Parks announced that Mr. De Mille had donated $3,760 for the project.