On 5/14/07, Ajinkya Kale <[EMAIL PROTECTED]> wrote:
> I asked this trivial question only for the reason that this question was
> asked in one of my orals and the examiner told me that DOS works in real mode
> and Windows in protected so the difference in the sizes of int.
> I dont think this is true...what do you all think?
He's right -- real mode was introduced with the 286 chip (to be
backward compatible with the 8086/8088 chips, which only had one mode
of operating, which is the same as what real mode is on later chips)
and this is what DOS runs in -- 20 bit segmented memory addressing,
only 1 meg of memory available (and for userspace applications, only
640k of that 1 meg). Technically, all CPUs 286 and higher start up in
real mode but then switch into protected mode to load operating
systems like Windows, Linux, FreeBSD, etc., and able to use 32bit
integers. Real mode uses 16 bit integers.
I wouldn't about real mode too much these days, you rarely would have
to use it. There is also a virtual 8086 mode, that is used to run
legacy DOS apps inside Windows or Linux, and it is also subject to the
same restrictions as the hardware-based real mode.
-- Brett
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"In the rhythm of music a secret is hidden;
If I were to divulge it, it would overturn the world."
-- Jelaleddin Rumi
