Write explanatory notes on Hard disk drive controller.

Hard disk drive controller: It converts instructions from software running upon the computer to the electrical signals needed to operate the hard disk. The function of a disk controller is track and sector selection, disk drive selection and head loading, parallel to serial conversion and to parallel of data and error checking. The data recorded in a magnetic disk is the combination of data and clock. Thus, data read should be separated from the clock information. The data processed through a CPU or stored in the main memory is into the byte form. The bytes to be recorded upon a magnetic disk should be converted in serial format.