Sleep mode has gone by various names, including Stand By (for Microsoft Windows 98-Server 2003), Sleep (for Mac OS 8-Mac OS X, Windows Vista, Windows 7, Windows 8, Windows 10, Windows Server 2008), Suspend (Windows 95) and Suspend to RAM (Linux). Machine state is held in RAM and, when placed in sleep mode, the computer cuts power to unneeded subsystems and places the RAM into a minimum power state, just sufficient to retain its data. Because of the large power saving, most laptops automatically enter this mode when the computer is running on batteries and the lid is closed. If undesired, the behavior can be altered in the operating system settings.
A computer must consume some energy while sleeping in order to power the RAM and to be able to respond to a wake-up event. A sleeping PC is a case of a machine on standby power, and this is covered by regulations in many countries, for example in the United States limiting such power under the One Watt Initiative, from 2010. In addition to a wake-up press of the power button, PCs can also respond to other wake cues, such as from keyboard and mouse.