But computers, particularly those running Windows, have always been more complicated. On is on, of course. For off, though, Windows XP machines offer several options--including hibernate, stand by and shut down.
"Users don't always understand the difference," said Pat Stemen, a program manager in Microsoft's core operating-system division.
With Vista, Microsoft is changing shut-down options so that pressing the power button feels more like turning the machine off.
The OS will typically send the computer to sleep rather than shutting down when the button is pressed to off--a power-saving move.
What's worse is that even when people do know enough to choose hibernate or stand by, which turn off most parts of the system but don't clear files away, the computer often ends up staying on. That's because today's Windows lets an application or hardware device veto a PC user's decision.
That won't be the case in Windows Vista, which is due for general release next year. (A , formerly known by the code name Longhorn, was released in late July.) Applications will be warned that a computer is entering sleep and have a second or two to save whatever they need to, but the programs won't get a say in whether the machine slumbers.
And with Vista, Microsoft plans to make it so that a PC seems more like all the other consumer electronics out there. Pressing the power button will give users the feeling they are either turning the machine on or turning it off.
In reality, pressing the button to off will more likely send the machine into some form of sleep mode than turn it off. PC manufacturers will be able to map a shut down or a sleep option to the button's off position--including several sleep modes being developed by Microsoft.
Microsoft says that the operating system change is needed because today's options aren't working. Despite the multitude of choices, Windows users either leave their machine on all the time or choose to shut it down, the company has discovered from customer feedback. People don't tend to opt for hibernate or stand by. As a result, they either waste power or have to suffer through the delay while Windows starts up again.
Stemen pointed to an all-too-typical scenario in which a mobile worker shuts his or her laptop, assuming it will go into stand by. But if any of the applications or some other system process vetoes the stand by request, the laptop could remain on, heating up and draining the battery--the whole situation could end in data loss.
When it's sleepytime
For Vista notebooks, the plan is for the machines to go into a stand by mode when the power button is turned off. In stand by, all the work the user has done is saved in the memory, and the machine receives enough power to keep that data there. If battery levels reach a critically low level, the laptop will power up enough to save the needed information onto the hard drive, and then it will power down completely.
Desktop machines will enter a mode Microsoft is calling "hybrid sleep." In this case, Vista will save the system state and other information to disk, just in case power is lost, but will then enter a sleep mode from which the computer can quickly be roused.
People will likely still be able to go to the start menu if they want to shut down the computer. But being able to send it into a particular kind of sleep at the push of a button will be a boon, said Greg Graceffo, a product manager in Microsoft's Windows client unit.
"For the end user, there is simplicity," Graceffo said. "All you really need to know about is sleep."
"The issue is the user experience," he said, noting that in the past computers have taken too long to turn on and off, meaning most people leave their machines on as much of the time as possible. "The cost for turning it off and on should be so low (that) people feel comfortable doing it."
In changing the settings, Microsoft is making some trade-offs. With Windows XP, if you try to put your machine to sleep while burning a CD, for example, the program can veto the attempt.
With Vista, applications won't have that option. That means PCs should go to sleep more reliably. But if people are burning Coldplay's latest album when they flip the switch, they're not likely to get a good copy.
"If you push the button, I think you are going to have a coaster," Graceffo said.
In part to address this issue, Microsoft is also developing a third mode, known as "away" mode, for media-centered PCs. In that setting, the user will push a button and the machine will look off and sound off.