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From: Tim Slattery <TimSlattery@utexas.edu>
Newsgroups: comp.os.ms-windows.misc,alt.comp.os.windows-xp,alt.windows7.general,microsoft.public.windowsxp.general
Subject: Re: Windows 32-bit
Date: Fri, 29 Dec 2023 11:31:31 -0500
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Steve Hayes <hayesstw@telkomsa.net> wrote:


>I think early programs running on IBM PC DOS or MS DOS were 8-bit,
>running on 8088 processors. The 286 and 386 ones were 16-bit. 

Not so. The original IBM-PCs were 16-bit machines. They used a kludge
to implement a 20-bit address space, allowing access to one megabyte
of RAM. You may remember that 340KB of that was reserved for the
operating system, leaving 640KB for user program.

1970's vintage machines, such as Cromemco, Zylog, etc, etc, were 8
bits. I'm a bit foggy on their addressing schemes, but at least some
of them could switch between banks of 64KB each.

The 80286 was basically 16-bits, but implemented "protected mode"
which allowed access to 16MB. Windows programers (if they're old
enough) may remember using "GlobalAlloc" and "GlobalFree" calls. Those
manipulated the Global Allocation Table, a 80286 protected mode
hardware kludge that kept track of all that RAM. 

The 80386 was Intel's first true 32-bit machine. Windows 3.0 386
version ran in 16-bit 80286 protected mode though. It took a while for
Windows to catch up with 32-bit processors.

-- 
Tim Slattery
timslattery <at> utexas <dot> edu