primary partition

primary partition

A reserved part of a Windows disk, which is identified by a drive letter. The entire C: drive is often one primary partition; however, multiple partitions are created for a user's own organizational purposes or for booting into different operating systems. See extended partition, master boot record, partition and basic disk.

Windows Primary Partitions
Depending on the boot method and partition tables used in the PC (MBR or GPT), from four to 128 primary partitions can be created. See MBR disk, GPT and UEFI.