HAL
The HAL 9000 has been compared to Frankenstein's monster. HAL is an artificial intelligence, a sentient, synthetic, life form. According to John Thurman, HAL’s very existence is an abomination, much like Frankenstein’s monster. "While perhaps not overtly monstrous, HAL’s true character is hinted at by his physical 'deformity'. Like a Cyclops he relies upon a single eye, examples of which are installed throughout the ship. The eye’s warped wide-angle point-of-view is shown several times — notably in the drawings of hibernating astronauts (all of whom HAL will later murder)."
Kubrick underscores the Frankenstein connection with a scene that virtually reproduces the style and content of a scene from James Whale’s 1931 Frankenstein. The scene in which Frankenstein’s monster is first shown on the loose is borrowed to depict the first murder by HAL of a member of Discovery One’s crew--the empty pod, under HAL's control, extends its arms and "hands", and goes on a "rampage" directed towards astronaut Poole. In each case, it is the first time the truly odious nature of the "monster" can be recognized as such, and only appears about halfway through the film.
Clarke has suggested in interviews, his original novel, and in a rough draft of the shooting script that HAL's orders to lie to the astronauts (more specifically, concealing the true nature of the mission) drove him "insane". The novel does include the phrase "He had been living a lie" — a difficult situation for an entity programmed to be as reliable as possible. Or as desirable, given his programming to "only win 50% of the time" at chess, in order for the human astronauts to feel competitive. Clarke also gives an explanation of the ill-effects of HAL being ordered to lie in computer terms as well as psychological terms, stating HAL is caught in a "Mobius feedback loop."
While the film remains ambiguous, one can see evidence in the film that since HAL was instructed to deceive the mission astronauts as to the actual nature of the mission and that deception opens a Pandora's box of possibilities. During a game of chess, HAL misstates what move is to be made (by using a hybrid of algebraic and traditional chess notation) and how many moves it will then take to mate him (assuming a move is forced that is not). Frank Poole is seen to be mouthing his moves to himself during the game and it is later revealed that HAL can lip read. HAL's conversation with Dave Bowman just before the diagnostic error of the AE-35 unit that communicates with Earth is an almost paranoid question and answer session ("Surely one could not be unaware of the strange stories circulating...rumors about something being dug up on the moon...") where HAL skirts very close to the pivotal issue concerning which he is concealing information. When Dave states "You're working up your crew psychology report," HAL takes a few seconds to respond in the affirmative. Immediately following this exchange, he errs in diagnosing the antenna unit. HAL has been introduced to the unique and alien concept of human dishonesty. He does not have a sufficiently layered understanding of human motives to grasp the need for this and trudging through the tangled web of lying complications, he falls prey to human error.
The follow-up film 2010 further elaborates Clarke's explanation of HAL's breakdown. While HAL was under orders to deny the true mission with the crew, he was programmed at a deep level to be completely accurate and infallible. This conflict between two key directives led to him taking any measures to prevent Bowman and Poole finding out about this deception. Once Poole had been killed, others were eliminated to remove any witnesses to his failure to complete the mission.
One interesting aspect of HAL's plight, noted by Roger Ebert, is that HAL, as the supposedly perfect computer, actually behaves in the most human fashion of all of the characters. He has reached human intelligence levels, and seems to have developed human traits of paranoia, jealousy, and other emotions. By contrast, the human characters act like machines, coolly performing their tasks in a mechanical fashion, whether they are mundane tasks of operating their craft or even under extreme duress as Dave must be following HAL's murder of Frank. For instance, Frank Poole watches a birthday transmission from his parents with what appears to be complete apathy.
Read more about this topic: Interpretations Of 2001: A Space Odyssey