Why does my computer sometimes blackout?

If I'm using my computer, and a power blackout occurs, is my computer damaged (besides losing recent data)?

• Answer:

  I have to disagree with damaging the hard-drive when a blackout occurs. Modern hard-drive design has eliminated that effect. It is true the heads are tensioned by springs to contact the platters, and the 5400/7200/10000 rpm spinning of the disk cause the heads to "float" mere nanometers above those platters. However; when power is suddenly disconnected, the internal hard-drive circuitry senses this, by using a voltage threshold algorithm and sends the heads to their "parked" position. The power to accomplish this is derived by a combination of the remaining momentum of the platters, and remaining stored energy in capacitors located both in the hard drive and power supply. Yes, the power supply also. A Power supply does not instantenously black out due to filter capacitors on it's output. The hard-drive has sensed the loss of power way before the power supply has gone to zero output. All this is happening in milliseconds. The parking result is almost instantaneous. Layman terms used throughout this of course. Damage to hard-drives mainly come from moving the computer/hard-drive while the disk is running. This causes the head to "bump" the platter, and possibly damaging the sectors it contacts. This effect is cumulative and usually doesn't "wipe out" a hard-drive. It only reduces the area the OS can write to, reducing the disk's capacity. The only damage that should occur on a blackout in modern systems is as you've already mentioned - a loss of any data stored in memory which hasn't been written to the drive at the time.