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

Marko Rauhamaa marko at pacujo.net
Fri Oct 13 12:23:05 EDT 2017 
alister <alister.ware at ntlworld.com>:

> On Sat, 14 Oct 2017 01:48:44 +1300, Gregory Ewing wrote:
>> I thought it would be fairly obvious that by "put it in read-only
>> memory" I meant "arrange for it to be in a location that is read-only
>> at run time". Obviously it can't be read-only at *compile* time, just
>> as a physical ROM can't be read-only at manufacture time.
>
> oh yes it can
> [...]
>
> I doubt that either process is in widespread usage any longer as most 
> manufacturers no incorporate a way to update the firmware of a device 
> (usually with flash memory)

Then there's the case of FPGA, which can expose parts of itself as
memory, whether writable or read-only. You can reprogram its ROM (and
other) parts, but not using the regular RAM write mechanisms.

In general, memory-mapped I/O may be read-only to software. For example,
you could read dip-switch settings or the error counts of a hard disk
from "const volatile" memory areas. There, "const" means you can't write
into it and "volatile" means it could change "by itself".


Marko
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