Complex sentence: GLaDOS (Genetic Lifeform and Disk Operating System) is a fictional artificially intelligent computer system appearing in the video games "Portal", "Portal 2", "The Lab" and "Lego Dimensions".
Split into simpler sentences: GLaDOS (Genetic Lifeform and Disk Operating System) is a fictional artificially intelligent computer system from the video game series "Portal". GLaDOS later appeared in the "The Lab" and "Lego Dimensions".