C:
The designation for the primary hard disk in a PC. The "C" evolved from the early personal computers that used A: and B: labels for two floppy drives. When hard disks became available, they were named C:. For a while, PCs came with the older 5.25" and newer 3.5" floppy drives, and A: and B: were still used. Subsequently, the 5.25" drive was dropped, leaving a hole in the middle between A: and C:. Today, PCs often come without floppies, leaving the A: and B: designations for the history books.
Letters starting with D: and up are used for CD-ROM and DVD drives or other removable media such as Zip disks. Sometimes the hard disk is divided into two logical disks, thus, C: and D: may refer to the same physical drive.
