The message of the day is stored in a file called

Unix is a family of multitasking, multi-user computer operating systems that derive from the original AT&T Unix, whose development started in 1969 at the Bell Labs. The main features of UNIX were its simplicity, portability (the ability to run on many different systems), multitasking and multiuser capabilities, extensive library of software, and hierarchical file system. The Full Form of UNIX (also referred to as UNICS) is UNiplexed Information Computing System.