The hard disk is a hardware device that stores all the data on a computer. The data is stored in the form of files and directories in the hard disk. A hard disk drive has a logical structure that is compatible with the operating system installed. The Master Boot Record is the most important part of the hard disk. It is the first sector on the hard disk that the operating system accesses. The Master Boot Record contains the Boot Loader and Partition Tables. It is important to know about the logical structure of the hard disk to gain better understanding and fix issues related to the hard disk drive.