This Day in sci-fi history

Doctor Who first appeared on BBC television at 5:15 pm (GMT) on 23 November 1963.

Doctor Who originally ran for 26 seasons on BBC1, from 23 November 1963 until 6 December 1989. During the original run, each weekly episode formed part of a story (or "serial") — usually of four to six parts in earlier years and three to four in later years. Three notable exceptions were the epic The Daleks' Master Plan, which aired in twelve episodes (plus an earlier one-episode teaser, "Mission to the Unknown", featuring none of the regular cast); the 10-episode serial The War Games and The Trial of a Time Lord which ran for 14 episodes (containing, according to BBC serial codes three stories, two four-parters and a six-part finale, but in both the re-edited feature compilation versions and the novelisations four stories, three four-parters and a two-part finale often referred to by individual titles; the preliminary stories are connected by framing sequences which become the focus of the last two episodes) during Season 23. Occasionally serials were loosely connected by a storyline, such as Season 16's quest for the Key to Time or Season 18's journey through E-Space and the theme of entropy.

The programme was intended to be educational and for family viewing on the early Saturday evening schedule. Initially, it alternated stories set in the past, which would teach younger audience members about history, with stories set either in the future or in outer space to teach them about science. This was also reflected in the Doctor's original companions, one of whom was a science teacher and another a history teacher.

However, science fiction stories came to dominate the programme and the "historicals", which were not popular with the production team, were dropped after The Highlanders (1967). While the show continued to use historical settings, they were generally used as a backdrop for science fiction tales, with one exception: Black Orchid set in 1920s Britain.

The early stories were more serial-like in nature, with the narrative of one story flowing into the next, and each episode having its own title, although produced as distinct stories with their own production codes. Following The Gunfighters (1966), however, each serial was given its own title, with the individual parts simply being assigned episode numbers. What to name these earlier stories is often a subject of fan debate.

Writers during the original run included Terry Nation, Henry Lincoln, Douglas Adams, Robert Holmes, Terrance Dicks, Dennis Spooner, Eric Saward, Malcolm Hulke, Christopher H. Bidmead, Stephen Gallagher, Brian Hayles, Chris Boucher, Peter Grimwade, Marc Platt and Ben Aaronovitch.

The serial format changed for the 2005 revival, with each series consisting of thirteen 45-minute, self-contained episodes (60 minutes with adverts on commercial channels overseas). This includes three two-parters and a loose story arc per season whose elements are brought together in the season finale. Like the original serial format in the William Hartnell era, two-part episodes have separate titles.

737 Doctor Who instalments have been televised since 1963, ranging from 25-minute episodes (the most common format), to 45-minute episodes (for Resurrection of the Daleks in the 1984 series, a single season in 1985, and the revival), to two feature-length productions (1983's "The Five Doctors" and the 1996 television movie), to the two 60-minute Christmas specials produced for the revival.

The current series is recorded in 576i25 DigiBeta wide-screen format and then filmised to give a 25p image in post-production using a Snell and Wilcox Alchemist Platinum.
source: thefreedictionary.com