dBase II was the first widely used database management system (DBMS) for microcomputers. It is a relational database management system. It was originally published by Ashton-Tate for CP/M, and later on ported to the Apple II and IBM PC under DOS. On the PC platform in particular it became one of the best-selling software titles for a number of years, propelling Ashton-Tate to become one of the "big three" software publishers in the early business software market. A major upgrade was released as dBASE III, and ported to a wider variety of platforms, adding UNIX, and VMS.