Date   : Tue, 31 Jul 2001 11:08:18 +0100
From   : Paul Wheatley <p.r.wheatley@...>
Subject: Re: BEEB Stuff

Jonathan wrote: 
> You emulate HARDWARE.  The emulated HARDWARE, may then EXECUTE software,
> such as BBC Basic.  An EMULATED IBM-PC running on RISC-OS can EXECUTE
> microsoft Word.  The Arc. isn't EMULATING Microsoft Word, the emulated
> IBM-PC is EXCUTING Microsoft Word.  It's like saying DOSFS is an emulation
> of MS-DOS.  It's not, it's an implementation of DOSFS.

The distinction between emulating software and recreating software can become
blurred and I think the BBC Basic issue you're talking about is a good
example of this.

But to say that you can only emulate hardware and that its impossible to
emulate software is misleading and to be honest not very helpful in getting
the concepts across. An example of an emulator which includes elements of
hardware emulation and software emulation is my colleague's George3 emulator,
details of which can be found in Emulation, Preservation and Abstraction
here:
http://www.leeds.ac.uk/camileon

The software in question is (arguably) not an implementation of a 1970s ICL
machine (or its software) but is in fact an emulation. Some of the hardware
is emulated (eg the processor and the execution of instructions) and some of
the hardware's functionality is actually emulated at a higher level, namely
the software of the executive API. Effectively abstracting out a lot of the
unnecessary low level complexity. It can be argued that this makes the
emulator and its processes more understandable as it is the higher level
functions that are emulated rather than the underlying nitty gritty of how
these functions were implemented in hardware.

Paul
-- 
Camileon Project Officer
http://www.si.umich.edu/CAMILEON/
http://www.leeds.ac.uk/camileon
0113 233 5830