According to official information, one advantage the Calculator had over normal computers was the electro-organic linking terminal. The CPU could share tasks and receive data from pseudo-cryogenic stored brains maintained in an oxygenated tank.
These brains were initially those of lab rodents, but calculations eventually indicated that human brains could be preserved in the same fashion. The brains were fed specifically formulated nutrients to sustain suspended life. In turn, they assisted the Calculator's CPU in vault management, including life support, food production and distribution, Vault 0 defenses, and "pacification protocol". The brains of the eight most promising humans of Vault 0 were chosen to become one with the Calculator:
The neural network was also meant to assist in Vault 0's primary function: to initiate humanity's post-war rebirth. When the outside temperature, radiation levels and poison particle counts returned to acceptable levels, Vault 0 was to remotely activate the Exodus protocol, which would initialize the integration of all vault dwellers with the planet's surface. Additionally, the Calculator was entrusted with an army of robots that it could use to assist in the protocol. However, it was a plan that never came true. The Calculator became corrupted due to fatal errors in its CPU and data storage systems - human brains. The cybernetic machine became a mad personality, whose goals turned rather homicidal.
Many of Vault 0's citizens were killed by the Calculator, while those who survived had brain damage due to the lack of backup life support systems to their cryogenic chambers. Unfortunately, such systems were scrapped during streamlining of the vault's construction, to be replaced by leisure facilities and to provide pay raises to senior committee members. Taking full control of the Vault 0, the Calculator awaited the beginning of the Exodus protocol.
The Exodus protocol could also be triggered by a breach of the vault's defenses, as was the case when the Eastward-fleeing super mutants stumbled upon Vault 0; this awoke the Calculator completely. The cybernetic being proceeded to enact its
"pacification protocol", considering all life to be its enemies. The Calculator activated its nuclear reactor in Buena Vista and constructed many robot manufacturing and repair facilities across the wastes. Soon, the Chicago region was full of rumors of a Menace from the West, coming to exterminate all life.
The Calculator discovered a useful ally in a captured Midwestern Brotherhood of Steel General named Simon Barnaky, who began to see the machine as the only hope of restoring order. Barnaky was transformed into a humanoid robobrain and began his service to the Calculator as its adviser and guardian.
Although the Calculator had begun rapid expansion and had attempted to eliminate the Midwestern Brotherhood of Steel, Vault 0 was breached by Brotherhood forces led by the Warrior. There, the Warrior defeated the robots and Simon Barnaky's new form, and entered the Calculator chamber. The eight brains crucial to the Calculator were destroyed, so the Calculator required a new brain to continue to function. From here on, the warrior had three choices, which determined the game's ending.
Merge with the Calculator, taking control of it and using its resources for the Brotherhood.
Allow Simon Barnaky to merge with the Calculator, which would result in a new Brotherhood of Steel and anti-mutant regime.
Do nothing, allowing the Calculator to shut down forever, or destroy it using weapons.
"Greetings. I am the Calculator, overseer of the Vault Network. You have proven to be a statistical anomaly that crashed my logistics programs time and time again. It is my admiration of your adaptation and ingenuity that brings you to me. I assume that you would agree that ten Behemoth robots would terminate you and your squad? I have the resources to make such an offensive, but it is not in my interest. After all, you are quite the remarkable human and, more importantly, you have something I need."
"It is the organic portion of my mainframe that has become corrupted. The degeneration of my symbiotic brains has corrupted eighty-five percent of main protocol programming. It would take only one brain to bring my organic subsystems back online, but finding a feasible brain has become a problem. I would use a brain from one of Vault 0's residents, but I compute that my CPU would only become less efficient."
"However there is another solution. Yours is a brain can bring balance to my organic neuro-network. I am offering you what you humans call a "dream come true." You can shed your mortal shell and join with me. You will share my power and resources to save humanity and restore civilization from the smoking ruins of the wasteland. Your name will never be forgotten and be synonymous with the word "hero.""
"What say you, warrior? Will you continue to fight me? Destroy me and continue to carve some small, insignificant niche for the Brotherhood? While the Brotherhood may tame a region, they will never have the lasting impact I alone can. The machinery you see before you has the capacity to remove your brain from its mortal vessel. It is in this machine that your journey to save mankind will truly begin. You must hurry, human. My systems cannot function long without a symbiotic brain."
Incidentally, the story of Tactics went through a lot of revisions. For example, my original concept for the main villain, the Calculator, was for it to be a completely unfeeling automated system, not even a computer so much as an engine designed to tick over and perform certain tasks after doomsday. Totally implacable, and therefore the fault of everything bad that happens is still in the hands of the humans.