A compact operating system that provides immediate access to the Internet via a browser as soon as the power is turned on. It also allows access to local applications such as a media player or photo editor. Typically a Linux version, it enables users to turn their computers on and quickly retrieve e-mail, look up something on the Web or play music without waiting the long time it takes to boot up the primary operating system, which is usually Windows.

For example, Latitude ON is Dell's version (www.dell.com), which also uses a separate ARM processor in the laptop. DeviceVM's Splashtop (www.splashtop.com) includes Skype, a music player and photo editor. Phoenix Technologies' HyperSpace (www.hyperspace.com) runs side by side with Windows Vista (see HyperSpace). See instant-on.