It is called a block (or sector). The size of the block varies depending upon the size of the disk, advanced preferences (the size of files normally being used on that disk), and the filesystem being used. They normally run from 512Bytes to 64KiB. As disk capacity continues to grow, look for even larger block sizes to come :-)
The smallest addressable unit of storage on a disk is called a sector.
program
It all depends on how your disk is formatted.
The smallest storage access unit on an IDE hard drive is a sector.
Sector
One bit.
Hard Drive Disk (HDD)
Hard Drive Disk (HDD)
Hard Drive Disk (HDD)
sector
Sector is the smallest unit on Hard disk identified & addressed by File System.
In digital imaging, a pixel is a single point in a raster image, or the smallest addressable screen element in a display device; it is the smallest unit of picture that can be represented or controlled