ARCHIVED: In DOS, what were the differences among the versions before 6.0?

• DOS 1.0: This version of DOS was meant for the early dual floppy IBM PCs, and was shipped on 160K, 8 sector, single-sided double density diskettes. It was only capable of reading and writing to 8-sector 5 1/4" diskettes, which held 320K. Support for Winchester drives was nonexistent, requiring the drive manufacturer to supply patched copies.
• DOS 2.0, 2.1: This version introduced 9 sector (360K) diskettes, Winchester support, and installable device drivers. This was probably the best system to use if you had a two-floppy system because it took up less space on RAM and on diskette than later versions. For hard drive systems, the large minimum cluster size wasted hard drive space.
• DOS 3.0, 3.1, 3.2: DOS 3.0 through 3.2 were very much alike. These versions introduced a smaller cluster size and handled hard drives a little better. DOS 3.0 through 3.2 also added programs (e.g., label.com and vdisk.sys).
• DOS 3.3: This version is the first to provide built-in support for 3 1/2" diskettes, 720K drives only, but essentially very much like DOS 3.0. Maximum hard drive partition size for DOS 3.3 is 32MB, making it necessary to split up large drives.
• Zenith DOS 3.3+: Zenith's DOS versions had unusual features, many of which were specific to Zenith hardware. Zenith DOS 3.3+ used the large hard drive partition size supported by DOS 4.0.
• DOS 4.0: DOS 4.0 was a major upgrade. It allowed the use of large hard drive partitions (greater than 32MB) and included a text shell. It also included support for LIM EMS 4.0, EMS emulation on 80386 computers, and nesting of batch files (using the CALL command).
• DR-DOS 5.0: DR-DOS was an alternative operating system developed by Digital Research, Inc. It had many enhancements over MS-DOS, including a full-screen editor, command history buffer, and the ability to load device drivers high.
• MS-DOS 5.0: Released in 1991, MS-DOS 5.0 introduced many features that were first seen in DR-DOS 5.0. Many of the commands had the same parameters used in DR-DOS. It had the ability to load device drivers high, a full-screen editor, file undelete support, accidental format recovery, file deletion history, task switching, a new shell, improved basic support, and command history.

Note: Most versions of DOS had many variants of their own, e.g., OEM (which was packaged with most machines) and generic versions. Most versions worked with other brands; however, you should avoid mixing files from different brands of DOS (e.g., PC-DOS and MS-DOS) even if they have the same version number.