A portion of a disk that cannot be used because it is flawed. When you format a disk, the operating system identifies any bad sectors on the disk and marks them so they will not be used. If a sector that already contains data becomes damaged, you will need special software to recover the data.
It s not unusual for a hard disk to leave the manufacturing process with a damaged sector; however, this does not affect the overall performance of the disk as the damaged space is considered unusable.
