Glossary of PC terms:A

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Actuator	The internal part of the drive that moves the read/write element from one location to another. Today's hard disk drives are equipped with the voice-coil actuators (VCA) that are much faster than the previously used step motor.  A typical drive's VCA consists of a rotary voice coil and the element mounting arm. As current is applied to the rotor, it rotates, positioning the heads over the desired cylinder on the media at frequencies of 50 Hz or more.
Access time	See average access time
Adaptive Battery Life Extender	A technology used in mobile hard disk drives to reduces power consumption by approximately 20 percent. It is accomplished by adapting power mode transitions based on the access patterns of individual users, rather than relying on conventional timers. As a result the power consumption may be lowered and battery life increased.
Address mark	Two byte address at the beginning of both the ID field and the data field of the track format (for HDD).
AFM (Atomic Force Microscope)	Physical tool for measurements of nano-topography and nano-forces on surfaces. Basically, the AFM consists of a thin, short lever with a few microns long sharp tip at the end. The tip's radius is usually of the order of a few nanometers.  When this tip is brought in proximity to the surface, surface forces act on the tip and result in bending and torsion of the lever which is measured with various techniques (mostly optically). The bending and torsion provides the nano-topography and nano-forces.
Air-bearing slider	A small ceramic slider with a self-pressurized air-bearing and magnetic element at the end.  When a magnetic rigid disk starts spinning, lift force is generated between the slider and disk which makes the slider fly at a very small height of a few dozen nanometers. This slider design was used in the first IBM "Winchester"-type hard drives that revolutionized drive technology.
ANSI	American National Standards Institute represents the United States in the International Organization for Standardization (ISO) and work on coding and signaling standards.
Areal density	Important indicator of the disk (and drive) performance. Corresponds to the number of magnetic bits per unit area usually measured in inches.
Asynchronous Data Transfer	A data transfer scheme which allows packets of data to be transferred after receiving a response from the receiving device. The retries are mandated if errors occur. This method sacrifices transfer speed for  reliability. See also synchronous data transfer, and isochronous data transfer.
ATAPI (Advanced Technology Attachment Packet Interface)	Is a type of interface used to connect additional hardware devices to a computer. This is an internal interface that is commonly used to connect devices such as CD-ROMs, hard drives, tape drives, and Zip drives. The advantages of ATAPI are that it is economical and offers high performance. To install an ATAPI device you must open your computer case and be able to identify the IDE channel on your computer's motherboard.
ATA/ATA-1 (Advanced Technology Attachment)	ATA is the official name given by ANSI to the IDE interface.
ATA-2/Fast ATA-2	ATA-2 is also known as enhanced  IDE and includes DMA mode 1, and PIO mode 3.  Fast ATA-2 includes upgrades in DMA and PIO modes.
ATA-3	ATA-3 is an update to the ATA-2 standard and includes SMART capability.
ATA-4	ATA-4 is an update to the ATA-3 standard and includes UltraDMA capability.
Average access time	The average delay within the drive between receiving a write or read command and the instance when the head begins reading or writing.  The access time includes seek time, settling time, and latency.

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