How do hard drives store data?
Ok Basically a hard drive is a series of magnetized circular platters. The platters spin and there is an arm that moves back and forth so that its head can touch any part of the platters. When data is written to the drive it is written in a series of ones and zeros. To accomplish this a electric current is sent down the head and through a coil of wire at the head of the arm the current create a magnetic field which changes the polarity of the magnetic field that area of the platter. When reading from the disk the head scans the disk and the magnetic field of the platter cause a current to travel from the coil of wire back up the arm and the polarity shift causes fluctuations in the current which can be translated into ones and zeros. Now because of limitations of equipment and slight variations of speed on the spin disks long runs of ones or zeros can be misread which is where RLL encoding comes in basically it ensures that the long runs of ones or zero’s do not appear. Where PRML is a
