The Swan computer was located inside The Swan, and was used for entering the Numbers every 108 minutes, according to the protocol set forth in the Orientation film. Assumed to be about 30 years old at the time of its encounter by the survivors, the computer was a composite of vintage computing devices, and usually had a cursor ">:█" flashing on the upper left corner of the screen.
A piece of the orientation film found by Eko, and later spliced into the movie by Locke, warned that the computer wasn't to be used for anything other than entering the code, and must never be used to contact the outside world. Nonetheless, communication via the computer was possible, as Michael communicated with Walt while he was on shift in the Hatch. ("What Kate Did") It appears that Michael activated chat mode by simply banging on the keys until the computer displayed a chat interface, or it may have been activated by the other end. ("The 23rd Psalm") Although, as Locke had shown him earlier, typing anything before the 104-minute mark didn't have any effect. It is likely that DharmaTel, which was referenced on the blast door map, is or was an Island-wide network of connected computers that connected the Swan computer to other stations.
After the survivors had made their way into the Hatch, Kate ended a standoff between Desmond, Jack, and Locke by striking Desmond with the butt of a gun, causing him to fire a shot and hit the computer. After blowing a fuse and shorting out the computer by attempting to power it up, Desmond panicked and fled, leaving Sayid to come and fix the computer just in time for the Numbers to be entered. ("Orientation")
After Desmond had returned and was convinced that the button needed to be pushed to prevent a catastrophe, Locke destroyed the computer by throwing it to the floor in an attempt to stop him from pushing the button. It was this breakage which led Desmond to trigger the fail-safe mechanism, causing the Swan station to implode. ("Live Together, Die Alone, Part 1")
- The main unit appears to be an Apple II Plus running an Apple III monitor with a Disk II floppy drive. The large lighted panel behind it is composed of sections of the SAGE computer, built by IBM for the US Air Force in the late 1950s. This particular prop has been used in many other productions, most recently Return to the Batcave, Austin Powers: Goldmember, Fail Safe and Austin Powers: The Spy Who Shagged Me.
- The Apple II was one of the more successful personal computers that were manufactured in the 1980s.
- The original came standard with 16K RAM, but most were upgraded to 48k. Later, the II Plus shipped natively with 48k. It could only run one program at a time.
- When the main unit is opened up for repair, it is said that the motherboard has been replaced.
- The Apple II Plus' keyboard has been modified for the show, with the right "SHIFT" button replaced by an "EXECUTE" button.
- The other machines in the Hatch's computer room appear to be mainframe components, including IBM 3420 magnetic tape drives; their 9-track spools are visible on the input desk but never used. The tape drives spin often, without any sign that tapes ever complete reading or writing or wear out.
- There is another computer cabinet, seen in "Live Together, Die Alone, Part 1", which is related to the control of the speakers and blast doors. The parts of this computer are far more modern than the other systems in the Hatch. The circuit boards inside make extensive use of Surface-Mount Technology (SMT) and Very Large Scale Integration chips (VLSI), both technologies which would not have been invented at the time the other parts of the Hatch were built.
- Many of the other parts are from the former United States Air Force AN/FSQ-7 (SAGE) radar defense system decommissioned in 1983; the props frequently show up on various television programs, mostly of the science-fiction variety. Mike Loewen's Q7 page The parts from the USAF SAGE shown in Lost include power panels, a Manual Drum Tester, and radar panels 
- Next to the Magnetic tape mainframes to the left side of the sage is a pair of 502A Dual-Beam Oscilloscopes.
- Lynnanne Zager was the voice actor who dubbed the voice during the lockdown incident.
- Technically, the Numbers are not entered every 108 minutes, because if the Numbers are entered four minutes early, then the Numbers have been entered after 104 minutes.
- The mainframes appear to be inconsistent with the environment in which they were placed. If the tapes behind the computer were magnetic, then it is likely that the strong electromagnetic fields within the hatch would erase any data stored on the tapes.
- The command line for the computer " >: ", when converted to Windows Wingdings font, gives characters of an Apple II-esque terminal and a tape reel.
- A 1980s film used in some psychology classes today called "The Self" features an Apple-III computer monitor that is used to test the effect of positive personalities.[source needed] Incidentally, the numbers 4, 8, 16, and 23 appear frequently in these tests. This could be the reason for the choice of the kind of computer.
- For fan theories about these unanswered questions, see: Swan computer/Theories
- Why did the Swan Orientation film warn users not to try to use the computer to communicate with the outside world?
- How did the computer go into chat mode?
- Countdown timer
- Fan-made countdown timers
- Flame computer
- Log printout
- Pearl computer
- Push the button
- Swan Orientation film