6.00 DOS Operating System Microsoft MS-DOS 6.00 (1200K Disk 1) MS-DOS 6.00 (1200K Disk 2) MS-DOS 6.00 (1200K Disk 3) MS-DOS 6.00 (1200K Disk 4) MS-DOS 6.00 (1440K Disk 1) MS-DOS 6.00 (1440K Disk 1) MS-DOS 6.00 (1440K Disk 1)