+-------------------------------+
               |     HISTORY OF DOS (Brief)    |
               |    (c) Thomas Freer-Heeter    |
               +-------------------------------+

WHY DOS 3.3 AS MINIMUM?   I wrestled for hours with what DOS
version to make as the minimum acceptable version.  To help
those souls who may come after me, I am writing down the con-
siderations of WHY I did not select the DOS 1 series or DOS 2
series as the minimum operating system platform for any purpose
(except for a museum exhibit perhaps).  I've tried to keep this
as short as possible while giving you a feel for the major
functionality limitations of DOS 1 & 2.
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DOS 1.0/1.1          DEVELOPED FOR THE IBM PC (1981)
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            -DOS 1.0/1.1  ONLY ran on 160K & 320K floppy disks
            -DOS 1.0/1.1  did NOT support ANY hard drive
            -DOS 1.0/1.1  did NOT support ANY 3.5" floppy disks
            -DOS 1.0/1.1  did NOT support any executables > 64K
            -DOS 1.0/1.1  ONLY supported an 8 bit BUS
            -DOS 1.0/1.1  ONLY supported 3 expansion slots
            -DOS 1.0/1.1  did NOT support BATCH files

 ** MSDOS ver 1.25 same as IBM DOS 1.1

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DOS 2.0/2.1         DEVELOPED FOR THE IBM PC-XT (1983)
-----------------------------------------------------------------
            -DOS 2.0/2.1  supported one 10 MEG hard drive MAX
            -DOS 2.0/2.1  did NOT support ANY 3.5" floppy disks
            -DOS 2.0/2.1  ONLY supported an 8 bit BUS
            -DOS 2.0/2.1  ONLY had INDIRECT foreign lang support
            -DOS 2.0/2.1  ONLY supported COM1 & COM2
            -DOS 2.0/2.1  did NOT directly support battery CMOS
            -DOS 2.0/2.1  did NOT support networking AT ALL
            -DOS 2.0/2.1  supported 9600 baud modems MAX

 ** DOS 2.0/2.1 DID support the once standard 360K floppy

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DOS 3.0, 3.1        DEVELOPED FOR THE IBM PC-AT (1984)
    3.2, 3.3
-----------------------------------------------------------------
            -DOS 3.0-3.3  up to four 32 MEG drive partitions MAX
            -DOS 3.3      introduced COM1 thru COM4 support
            -DOS 3.3      introduced 19200 baud modem support
            -DOS 3.1      introduced support for network cards
            -DOS 3.0-3.3  introduced 16 bit ISA BUS support
            -DOS 3.2-3.3  introduced 3.5" floppy support
            -DOS 3.0-3.1  introduced 1.2M floppy support
            -DOS 3.2-3.3  DIRECT foreign language support
            -DOS 3.0-3.3  supported 640K memory MAX

 ** DOS 3.3 requires at LEAST 30K less memory than DOS4.0-6.0

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DOS 4.0-4.01            DEVELOPED BY IBM (1988)
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            -DOS 4.0-4.01  introduced memory support over 640K
            -DOS 4.0-4.01  introduced 2 GIG drive support

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DOS 5.0-5.1          DEVELOPED BY MICROSOFT (1991)
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            -DOS 5.0-5.1  rewrite of DOS, 7000 beta testers used
            -DOS 5.0-5.1  early DOS & CP/M functions re-written
            -DOS 5.0-5.1  geared toward "windows" functionality

 ** DOS 5.0/5.1 version abandoned some early DOS functions

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FINAL THOUGHTS:  As described above, most of the major hardware
compatibilities were finally resolved by the DOS 3 series. Note
that many command features were added up through DOS 3.3 not
described in this brief history. I anticipate that DOS 3 could
be well suited to some specialized hardware needing a small O/S
"footprint" like a single chip PC.  Also, DOS 3 supported CP/M
ported applications like Wordstar very well--File Control Blocks
and all.  So, I have left it in for that 1% chance.

                    --SMYTH78711@YAHOO.COM