A hard disk is a composite storage device that’s mad up multiple platters- flat disks that are highly reflective.

The platter stores data in the form of magnetised and demagnetised segments to indicate a binary zero or one.

Modern hard disk feature multiple platters with each set of platters being accessed using a read/write head. This head is responsible for the magnetization of each individual segment and these heads are attached to an arm that moves the head over the platter.

Data writing is achieved by subjecting the platter to magnetic flux by the write head which leads to the polarization of the platter.

The process is reversed for reading the magnetic field of the platter is picked up by the read head and is interpreted as data. As an analogy, consider the gramophones of days gone by a needle moved on the record to read and play songs.

The case is pretty much the same here except the read/ write heads don’t touch the platter ( that would be very dangerous ) they float on a cushion of air just above it.

And when it spins, it goes fast HDD platters spin more than 3,000 inches a second (approximately 270 km/h). The HDDs of today run at 5,500 or 7,200 rpm and the faster 10,000 rpm drives are becoming common.