(1)master:-It contains system level information for a SQL Server system and also contains login accounts and all system configuration settings. master is the database that records the existence of all other databases, including the location of the database files.

(2) tempdb - This database holds all temporary tables and temporary stored procedures. It also fills any other temporary storage needs such as work tables generated by SQ

(3)model - The model database is used as the template for all databases created on a system. When a CREATE DATABASE statement is issued, the first part of the database is created by copying in the contents of the model database, then the remainder of the new database is filled with empty pages. Because tempdb is created every time SQL Server is started, the model database must always exist on a SQL Server system.

(4)msdb - The msdb database is used by SQL Server Agent for scheduling alerts and jobs, and recording operators.