Technologies in 2001: A Space Odyssey well, such as a nervous breakdown—as Hal did in the film. Clarke noted that, contrary to popular rumor, it was a complete coincidence that each of the letters of Hal's name immediately preceded those of IBM in the alphabet. The meaning of HAL has been given both as "Heuristically programmed ALgorithmic computer" and as "Heuristic ALgorithmic computer". The former appears in Clarke's novel of "2001" and the latter in his sequel novel "2010". In computer science, a heuristic is a programmable procedure not necessarily based on fixed rules, producing informed guesses often using trial-and-error. The results can be false such
Technologies in 2001: A Space Odyssey adviser for the film. "2001" accurately presents outer space as not allowing the propagation of sound, in sharp contrast to other films with space scenes in which explosions or sounds of passing spacecraft are heard. "2001" portrayal of weightlessness in spaceships and outer space is also more realistic. Tracking shots inside the rotating wheel providing artificial gravity contrast with the weightlessness outside the wheel during the repair and Hal disconnection scenes. (Scenes of the astronauts in the "Discovery" pod bay, along with earlier scenes involving shuttle flight attendants, depict walking in zero-gravity with the help of velcro-equipped shoes labeled "Grip