Primary partitions are defined at the end of the first logical sector on a disk, while logical partitions are not. The location of the first logical partition definition is stored in one of the primary partitions, called an extended partition. Any additional logical partition is defined in the location specified along with the current logical definition. All are chained into one logical partition table for purposes of defining the overall partition layout. Whether a partition is logical or primary can affect drive letter assignments, and whether a bootloader can successfully boot a particular operating system or partition. Otherwise, there is no reason to differentiate between them. Once an operating system is booted, there is no functional difference.