For much of Portal, GLaDOS is a voice that acts as a narrator and guide for players. Her voice is robotic, but distinctly female. Her personality has been described as passive-aggressive, witty, and sinister. She has a number of system personality cores installed into her, partly in order to prevent her from killing anyone. Eventually, once the player encounters her, she is revealed to be a complex computer, with robotic parts hanging from a larger device. Once the player removes the first personality core, the morality core, GLaDOS' voice becomes less robotic and more sensual. It is revealed in the later portions of the game that she was originally conceived as a means for Aperture Science to compete with their competitors, Black Mesa. She was created as a device to de-ice fuel lines. However, she also has a fully-functional disk operating system. The AI of GLaDOS is installed as the Enrichment Center's central control computer, mounted in a large, sealed chamber alongside control consoles and an incinerator.