A bad sector is a sector on a computer's disk drive that cannot be used due to permanent damage, such as physical damage to the disk particles. It is usually detected by a disk utility software such as CHKDSK or SCANDISK on Microsoft systems, or badblocks on Unix-like systems. When found, these programs mark the sectors unusable and the operating system skips them in the future. Disk Drive is the afternoon show on CBC Radio Two. ... CHKDSK (command shortening of Checkdisk) is a command in DOS and Microsoft Windows systems which verifies a hard disk or a floppy disk for file system integrity. ... SCANDISK or Scandisk is a command in MS-DOS and Microsoft Windows systems which verifies hard disk or floppy disk for file system integrity. ... badblocks is a linux utility to check for damaged sectors on a disk drive. ... An operating system (OS) is a set of computer programs that manage the hardware and software resources of a computer. ...

A modern hard drive comes with many spare sectors. When a sector is found to be bad by the firmware of a disk controller, the disk controller remaps the logical sector to a different physical sector. In the normal operation of a hard drive, the detection and remaping of bad sectors should take place in a manner transparent to the rest of the system. When the operating system begins to detect bad sectors, in most cases, it means that the surface of the hard disk is failing and the drive has run out of spare sectors with which to remap the failed sector. There are a variety of utilities that can read the SMART information to tell how many sectors have been reallocated, and how many spare sectors the drive may still have.^{[citation needed]} Self-Monitoring, Analysis, and Reporting Technology, or S.M.A.R.T., is a monitoring system for computer hard disks to detect and report on various indicators of reliability, in the hope of anticipating failures. ...

A commonly held idea for operation with regard to for bad sectors is that automatic remapping of sectors only happens when a sector is re-written to or re-written with zero-filled data. The logic behind this is presumably that even if a sector is having trouble reading it may still be readable with data recover methods. However, if a drive knows that a sector is bad and the drive's controller recieves a command to write over it it will not reuse that sector and instead remap it to one of its spare-sector regions. This may be the reason why hard disks continue to have sector errors (mostly disk controller timeouts) until all the bad sectors are remapped: typically with an entire-drive zeroing of sectors.^{[citation needed]}