Sleep

Sleep mode is when a Macintosh uses very low power and suspend all hard drive movement. It is a little like Shut Down, except for the contents of memory -- whatever was on the Mac before it went to sleep -- remains.

Sleep mode, however, does not mean that it does not use up battery. It is possible, on laptops, to put a computer to sleep for a long time and lose all remaining battery charge.

On Windows laptops, Hibernation mode is even more complete than sleep and actually will not let any power be wasted.

To wake a Mac up, press a key or move the mouse. If a laptop has slept and needs waking, open its case and, if needed, press a key.

History
Sleep was an option from the very first Macintosh Portable, and remained in the laptops-only realm until the 1995 introduction of the PCI-based Power Macintosh computers. Today, all Macs can sleep normally.

Sleep versus Restart
Restarting a Mac (most notably an iBook or PowerBook is only needed in the following circumstances:


 * Upon the installation or removal of an AirPort Card or AirPort Extreme Card;
 * Upon the insertion of a PowerBook Duo into a DuoDock;
 * If the user wishes to use Mac OS 9 instead of Mac OS X (or the other way round);
 * If the user wishes to start with different extensions, control panels and startup items (Classic Mac OS only);
 * Upon the attachment or removal of an external monitor (this applies only with very old laptops, and does not apply to newer portables, especially all iBooks and relatively recent PowerBooks);
 * Upon the attachment of the laptop to a SCSI chain to make it part of a desktop Mac.