GLaDOS, short for Genetic Lifeform and Disk Operating System

Disk operating system

Disk Operating System and disk operating system , most often abbreviated as DOS, refers to an operating system software used in most computers that provides the abstraction and management of secondary storage devices and the information on them...

, is a fictional artificially intelligent

Artificial intelligence

Artificial intelligence is the intelligence of machines and the branch of computer science that aims to create it. AI textbooks define the field as "the study and design of intelligent agents" where an intelligent agent is a system that perceives its environment and takes actions that maximize its...

 computer system

Computer

A computer is a programmable machine designed to sequentially and automatically carry out a sequence of arithmetic or logical operations. The particular sequence of operations can be changed readily, allowing the computer to solve more than one kind of problem...

 in Valve Software's Half-Life

Half-Life (series)

The Half-Life series of video games share a science fiction alternate history. Nearly all of the games are first-person shooters on the GoldSource or Source engines, and most are linear, narrative, single-player titles....

video game series and the main antagonist in the video games Portal and Portal 2

Portal 2

Portal 2 is a first-person puzzle-platform video game developed and published by Valve Corporation. The sequel to the 2007 video game Portal, it was announced on March 5, 2010, following a week-long alternate reality game based on new patches to the original game...

. She was created by Erik Wolpaw

Erik Wolpaw

Erik Wolpaw is an American videogame writer. Erik along with Chet Faliszek were the two writers behind the now-defunct Old Man Murray video game commentary web site. As of 2011, he works for Valve Software in Seattle...

 and Kim Swift and is voiced by Ellen McLain

Ellen McLain

Ellen McLain is an opera singer and voice actress from Nashville, Tennessee, USA. McLain provides voices for many characters in several video games from Valve...

. She is responsible for testing and maintenance in Aperture Science research facility in both video games. While she initially appears to simply be a voice to guide and aid the player, her words and actions become increasingly malicious until she makes her intentions clear.