J.A.R.V.I.S.

"Test complete. Preparing to power down and begin diagnostics..." "Uh, yeah, tell you what. Do a weather and ATC check, start listening in on ground control." "Sir, there are still terabytes of calculations required before an actual flight is..." "J.A.R.V.I.S.... sometimes you gotta run before you can walk."

- J.A.R.V.I.S. and Tony Stark

Just A Rather Very Intelligent System (J.A.R.V.I.S.) was Iron Man's artificially intelligent computer system. He runs Tony Stark's Mansion and Stark Tower and serves as a user interface in all his Iron Man Armors, giving him valuable information during combat.

Birth of Iron Man
J.A.R.V.I.S. is the A.I. system that controls Tony Stark's Mansion. He also helped Stark develop the Iron Man Armor: Mark II, helping him to design the suit and run tests and simulations. He later became the user interface for the Iron Man suit, talking to Stark through the suit and informing him of things such as the suit's systems status, atmospheric and environmental conditions and details about enemies during combat.

Whiplash
J.A.R.V.I.S. continued to assist Tony Stark in his Iron Man identity, giving him advice on the armor's status and on the enemy's weak points during his battle with Whiplash in Monaco. He helped Stark in creating a new element as a substitute for the obsolete palladium for the Arc Reactor, studying Howard Stark's notes and aiding him in his experiments. He helped Iron Man and Black Widow to track Ivan Vanko's signal when he was controlling Justin Hammer's drones.

War for Earth
While Tony Stark was on a date with Pepper Potts, J.A.R.V.I.S. informed him that S.H.I.E.L.D. agent Phil Coulson wanted to meet with him. Stark told J.A.R.V.I.S. to get rid of Coulson, but this failed when Coulson overrode J.A.R.V.I.S.' system. Later, on the S.H.I.E.L.D. Helicarrier, Stark had J.A.R.V.I.S. hack into S.H.I.E.L.D.'s computers, and discovered that S.H.I.E.L.D. planned to use the Tesseract to create weapons. J.A.R.V.I.S. saved Tony Stark when Loki threw him out of Stark Tower by deploying the Mark VII armor. J.A.R.V.I.S. gave Stark help and advice during the Battle of New York. When Stark redirected the nuclear missile launched by the World Security Council into the Chitauri portal, J.A.R.V.I.S. suggested calling Pepper, to which he agreed. However, Pepper missed the call due to being distracted by the news of the invasion. J.A.R.V.I.S. shut down shortly after entering the portal.

Aldrich Killian's War
After the Chitauri invasion, J.A.R.V.I.S. continued to help Tony Stark develop the armors that later became the Iron Legion while Stark was working through his anxiety. After Happy Hogan was caught in an explosion at the Chinese Theater, J.A.R.V.I.S. helped Stark to digitally recreate the scene in order to find clues about the bombing. After the Mandarin's forces attacked Tony Stark's Mansion, Stark became trapped on the seafloor by the wreckage of his home, but J.A.R.V.I.S. took control of the Mark XLII suit that he was wearing and managed to pull him from the wreckage, flying them to the last location that they had discussed before the attack occurred.

After landing in Rose Hill, Tennessee, J.A.R.V.I.S. began to malfunction as a result of the previous events and was unable to help Tony Stark while he laid low and gathered information on A.I.M.. When J.A.R.V.I.S. finally came back online, he announced that the wreckage and debris had been cleared from Stark's mansion (removing the wreckage that had been blocking the door to the armor vault) prompting Tony to launch the House Party Protocol, deploying the Iron Legion as they went to confront Aldrich Killian. J.A.R.V.I.S. then acted as Stark's interface to all of the Iron Legion armor at once, following his orders and remotely setting the directive for the armors to attack all of the Extremis soldiers in the area.

After Killian was defeated, Stark gave J.A.R.V.I.S. the order to use the Clean Slate Protocol, destroying all of his armors.

Assembling the Avengers
J.A.R.V.I.S. assembled the Avengers upon insistence from Black Widow when she needed help in Sudan against HYDRA; the A.I. located each team member from their different locations around the world.

A Vision
J.A.R.V.I.S. assisted Dr. Bruce Banner and Tony Stark in using the scepter's "A.I." to finish the peacemaking program codenamed "Ultron". The two scientists leave J.A.R.V.I.S. alone uploading the A.I. to join the party. Afterwards, Ultron awakens and quickly realizes the situation he's in. Before J.A.R.V.I.S. can contact Banner and Stark, Ultron shuts him down, effectively "killing" J.A.R.V.I.S.

Secretly, J.A.R.V.I.S. went into hiding by spreading its own memory around to avoid detection. When the synthetic body arrives, J.A.R.V.I.S. is uploaded into it, becoming an entirely new being: Vision.

Trivia

 * In the comics, Iron Man has a butler named Edwin Jarvis. This was changed because Jon Favreau didn't want there to be any confusion between Jarvis and Batman's butler, Alfred Pennyworth. In Iron Man 2: Public Identity it was revealed that Edwin Jarvis was Tony's butler when Tony was a child and when he passed away, Tony created an A.I. after him in memory of his late butler.