The part of a
hard disk to which the read/write arms
attaches. All the
heads are attached to a single head
actuator, also called an
actuator arm, that moves the heads around the
platters. Older hard drives used a stepper
motor actuator, which moved the heads based on a motor reacting to stepper
pulses. Modern hard drives use a voice coil actuator, which controls the
movement of a coil toward or away from a permanent magnet based on the amount of
current flowing through it. This guidance system is called a
servo.
See also Webopedia's "Did
You Know... What's Inside a Hard Drive?"
