One of the disks in a hard disk drive. Made of aluminum or glass with a magnetic coating, each platter provides a top and bottom recording surface. There may be only one or several platters in a drive with each platter having its own pair of read/write heads. See
magnetic disk.
A Whole Lotta Platters
Although solid state drives (SSDs) have become mainstream, disk platters are likely to be spinning for quite a while. This earlier 5.25" drive with 14 platters held 9GB in total. Today's disk drives have a thousand times as much data in that same amount of platter space. (Image courtesy of Singapore Technologies.)
From Spinning Platters to Solid State
The tiny Microdrive is history, and hard disk drives will eventually follow suit. See
Microdrive and
microSD.