Microsoft first presented Windows to the public on November 10, 1983. Requiring two floppy disk drives and 192 KB of RAM, Microsoft described the software as a device driver for MS-DOS 2.0. By supporting cooperative multitasking in tiled windows when using well-behaved applications that only used DOS system calls, and permitting non-well-behaved applications to run in a full screen, Windows differed from both Visi On and Apple Computer's Lisa by immediately offering many applications. Unlike Visi On, Windows developers did not need to use Unix to develop IBM PC applications; Microsoft planned to encourage other companies, including competitors, to develop programs for Windows by not requiring a Microsoft user interface in their applications.