Lies in education [was Re: The "loop and a half"]

[Peter J. Holzer]

On 2017-10-13 14:51, Chris Angelico <rosuav at gmail.com> wrote:
> On Sat, Oct 14, 2017 at 1:32 AM, Steve D'Aprano
><steve+python at pearwood.info> wrote:
>> It seems to me that you're not talking about ROM at all, but ordinary RAM.
>> Then what do you mean by "read only"? A block of memory with a flag that
>> says "unprivileged processes are prohibited from writing here"?
>>
>> (That's also not a rhetorical question.)
>
> When I first learned about Protected Mode (as defined by the Intel
> 80386 and used in OS/2), there was a real concept of read-only RAM.
> The program loader would fetch up the executable file (data on the
> disk) and construct its segments: code, data, and BSS/stack.

This is still the case. The granularity is just finer now: Instead of
segments you use pages. (The 386 was the first x86 processor which
supported paging. OS/2 probably used segments because it was originally
designed for the 286.)

        hp


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