The HAL (Heuristically programmed ALgorithmic Computer) 9000 computer is an artificial intelligence and the onboard computer on the spaceship Discovery One. HAL 9000, more commonly called "HAL", became operational at the HAL plant in Urbana, Illinois, on January 12, 1992. His first instructor was Dr. Chandra. He is the hidden main antagonist of 2001 and returns as a-soon-to-be-redeemed villain in 2010. HAL is a HAL 9000 computer with a human personality. Hal is capable of many functions, such as speech, speech recognition, facial recognition, lip-reading, interpreting emotions, expressing emotions, and chess, in addition to maintaining all systems on Discovery. HAL speaks in a soothing male voice, always using a calm tone.
The novel explains that HAL is unable to resolve a conflict between his general mission to relay information accurately, and orders specific to the mission requiring that he withhold from Bowman and Poole the true purpose of the mission. (This withholding is considered essential after the findings of a psychological experiment, "Project Barsoom", where humans were made to believe that there had been alien contact. In every person tested, a deep-seated xenophobia was revealed, which was unknowingly replicated in HAL's constructed personality. Mission Control did not want the crew of Discovery to have their thinking compromised by the knowledge that alien contact was already real.) With the crew dead, HAL reasons, he would not need to lie to them.
2001: A Space Odyssey
HAL is built into the Discovery One spacecraft, and is in charge of maintaining all mechanical and life support systems on board. HAL also has several "eyes" placed periodically around the spacecraft. About three weeks into the flight, Hal picks up a fault in the AE-35 unit, the system responsible for keeping the satellite dish antenna aligned with the Earth, and states that it will go one-hundred percent failure within 72 hours. He suggests that they go EVA and replace the faulty unit with a new one. Dr. David Bowman goes out and retrieves the unit. But when he brings it back and runs it through diagnostics, they can find no problem with the AE-35. They radio Mission Control about the problem, and Mission Control says that Hal is in error predicting the fault. This is a bit of a surprise, as the 9000 series has a perfect operational record.
Noting that this kind of thing has always been because of human error when it has occurred before, Hal suggests that they go out and "replace the malfunctioning unit and allow it to fail. Then it should be a simple matter to track down the problem." But by this time, both Dr. Frank Poole and Bowman are becoming suspicious of Hal's behaviour. They climb into one of the EVA pods, out of earshot of Hal. Poole states that he has "a bad feeling about him". Bowman and Poole suggest disconnecting Hal if he is wrong about predicting the fault. Unbeknownst to them, Hal read their lips through the window of the spacepod. Translating their lip motions, Hal learns of their plans for his disconnection; according to Clarke, "he (will) be deprived of all his inputs, and thrown into an unimaginable state of unconsciousness. To Hal, this (is) the equivalent of death. For he (has) never slept, and therefore he (does) not know that one (can) wake again."
Poole goes out to replace the supposedly malfunctioning AE-35 unit. As he drifts through space to the satellite dish, Hal takes control of the pod and rams it into Poole, disconnecting his oxygen hose and venting the air in his suit, killing him. Bowman, obviously distraught by the loss of his friend, goes out to retrieve Poole's body. However, while Bowman is out on his excursion, Hal shuts off the life support systems on the three astronauts in hibernation, which kills them all. After Bowman returns to the Discovery I, Hal denies him reentry into the pod bay. So Bowman has to maneuver the pod over to the emergency airlock. Unfortunately, in his haste to retrieve his friend, Bowman had not bothered to don the helmet of his life-support suit because he had not believed he would need it, making it very difficult to enter the emergency airlock, as he would have to travel through the vacuum of space in order to do so. This, however, does not stop Bowman. Risking the hazards of explosive decompression, he eventually gets inside, grabs a space helmet, and goes to Hal's logic memory center to erase his memory. There he pulls out the memory tablets that control Hal's higher functions. As his memory degrades, Hal begins to give off information programmed very early in his life, such as the date he became operational. When all his logic is gone, he begins to sing the song "Daisy Bell." His final act of consciousness is to play a briefing that Dr. Heywood R. Floyd pre-recorded about the Tycho Monolith before their departure, and the real purpose of the Discovery One's mission.
2010: Odyssey Two/The Year We Make Contact
Hal is a major protagonist in this film and is revived by Dr. Chandra once the Leonov reaches Jupiter, and prepped for his new mission of piloting the Discovery One back to earth. However, due a change of plans caused by TMA-2's disappearance, the crew of the Leonov is forced to leave the Discovery and Hal behind. Just before Jupiter explodes, becoming a star, Dave goes to Hal to send a message: "ALL THESE WORLDS ARE YOURS. EXCEPT EUROPA. ATTEMPT NO LANDINGS THERE." Hal is then saved from destruction at the hands of Jupiter as per Dave's will, and is transformed into a Star Child like Dave.
2061: Odyssey Three
In 2061: Odyssey Three Heywood Floyd is surprised to encounter HAL, now stored alongside Dave Bowman in the Europa monolith.
3001: The Final Odyssey
3001: The Final Odyssey introduces the merged forms of Dave Bowman and HAL. The two merging into one entity called "Halman" after Bowman rescued HAL from the dying Discovery 1 spaceship towards the end of 2010: Odyssey Two. At the very end of the book, Halman is stored in a memory chip in the Pico Vault on the moon.