Disk packs can be inserted into a disk drive for temporary’ use or installed permanently within the drive. Such disks are called removable disk or fixed disks, respectively. Removable disks lend versatility to disk use. Because disks can be inserted and removed, the number of disks available for use with a drive is countless. Inside a disk drive the removable disk is less vulnerable to dirt and destructive elements in the environment. Fixed disks are built inside the computer case and sealed from the outside
environment to protect the disk. An access light on the front panel is turned on when
data is being read or written. Users are advised to park the drive before moving a computer with a fixed hard disk. Parking the access mechanism, shown in Figure 7.9, locks the disk drive’s read/write heads into place so the arm does not move after the computer is turned off.
One way of installing a fixed disk into a PC is to insert a hard card into an open expansion slot on the computer’s motherboard. A hard card is an expansion card with a small fixed disk built inside