RAM

RAM
Random Access Memory, a memory chip that allows any data to be stored and retrieved randomly, directly and individually (increasing the amount of RAM on a PC will improve the performance)

RAM Disc
Part of the RAM that is used as if it were a disk drive, RAM is faster than disk drives

Recalibrate
Function where the heads are returned to cylinder zero

R&D
Research and Development

RLL
Run Length Limited, a process which compresses data so that more data can be stored on a disk

RMA
Return Merchandise Authorisation

RPM
Rotations Per Minute, speed at which the disk spins

ROM
Read Only Memory, a memory chip that once programmed can be read and accessed, but cannot be altered (chip retains the information even when the power is turned off)

Rotary Voice Coil
component which controls the head movement

Rotational Latency
The time lapse between a head reaching the right track, and the disk spinning around to the correct sector / block where the data can be read/written by the head

Rotational speed (also RPM)
measure of the number of times a disk spins per minute

RWMRead-write Memory, this describes computer memory (usually chip) that can be both read from and written to