The Core

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The Core is the massive repository of knowledge found in the control room of every Halo installation, and, more practically, the computer system which stores this knowledge.

Purpose
The Core is the most indispensable part of a Halo. It directs and controls every other aspect of the ring world, and is the location that the rings may be activated by way of the Activation Index. Containment protocol dictates that the Index must be physically brought into contact with the Core by a Reclaimer. According to 343 Guilty Spark, he was not allowed to perform this action (although not that he couldn't) and Jiralhanae Chieftain Tartarus was seemingly unable to do so. Once the Index has been 'reunified' with the Core, the Installation's firing sequence begins. However, if the Index is forcefully removed before the fire sequence begins, all seven Halo rings go into standby mode, ready to be fired remotely from the Ark.

The Core seems to be restricted-access according to 343 Guilty Spark's protocol, and access by unauthorized AI constructs is strictly forbidden. An AI inside the Core has a surprising amount of control: Cortana was able to make 343 Guilty Spark fall to the floor just by waving her hand, indicating the ability to override some of the Monitor's powers.

Installation 04
Installation 04's Core was, at one point, inhabited by Cortana. While inside, she obtained a tremendous quantity of knowledge. Within an instant, this position enabled her to learn of the Flood and Captain Jacob Keyes's plight against them. More importantly, it enabled her to stop the installation from firing and steal the Index when John-117 had attempted to activate Halo's firing process.

Installation 05
During the Battle of Installation 05, Tartarus forced the captive Miranda Keyes to connect Installation 05's Activation Index with the installation's Core. As the Halo's firing process was initiated, the Index was moved to the beam in the center of the control room. Before the ring could fire, however, Keyes removed the Index from the beam, aborting Installation 05's firing sequence.

List of appearances

 * Halo: Combat Evolved
 * Halo: Combat Evolved Anniversary
 * Halo: The Flood
 * Halo 2
 * Halo: Ghosts of Onyx
 * Iris
 * Halo 3