hi bret , can you explain the differnece between real mode of operations and protected mode of operations. how does kernel react for real or protected mode of operations.
On 5/14/07, Brett W. McCoy <[EMAIL PROTECTED]> wrote: > > On 5/14/07, Ajinkya Kale <[EMAIL PROTECTED]<ajinkyakale_86%40yahoo.com>> > 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 > ---------------------------------------------------------- > "In the rhythm of music a secret is hidden; > If I were to divulge it, it would overturn the world." > -- Jelaleddin Rumi > > [Non-text portions of this message have been removed]
