DOS 4 4DOS DOS (disambiguation) DOS 3 (disambiguation) DOS 5 (disambiguation) IBM DOS 3.40 IBM DOS 4.00 IBM DOS 4.01 IBM DOS 4.02 MS-DOS 3.40 MS-DOS 4.0 (multitasking) MS-DOS 4.00 (IBM-developed) MS-DOS 4.01 MS-DOS 4.1 (multitasking) Russian MS-DOS 4.01 Salyut 4