primary domain controller (PDC)

primary domain controller (PDC): In a Windows NT domain, a domain controller running Windows NT Server 4.0 or earlier that authenticates domain logon attempts and updates user, computer, and group accounts in a domain. The PDC contains the master read-write copy of the directory database for the domain. A domain has only one PDC.

In a Windows 2000 or Windows Server 2003 domain, the PDC emulator master supports compatibility with client computers that are not running Windows 2000 or Windows XP Professional.