Re: An Apple a day...

Roland John Turner (rjturner@nospam.socs.uts.edu.au)
Thu, 11 Jan 1996 19:21:12 +1100 (EST)

pmeric@nospam.vnet.IBM.COM wrote:

[after someone else wrote]

> > Actually RUNNING? or just sitting in the background using RAM.
>
> Huh? So, when using WFW, do you think the background apps are actually
> running? I don't think so!!
>
> This is something Win95 has addressed to the degree that MS can claim
> the OS to be multitasking - ie. background apps can run, but not very
> well.

This is a pretty common misconception. Both Win3 and Win95 DO pre-empt.
In other words, background apps CAN be running. Several bits of Win3 would
work even less well if this wasn't the case.

What DOS/Win3 lacks (and what every other O/S I've ever used does not
lack, apart from CP/M, 161OS and ProDos) is a re-entrant filesystem.
The result of this is that, the moment one process starts a disk access,
no other process can use the file system. In Win3 with 16 bit disk access,
the situation is actually worse - the CPU does a reset to switch back to
real mode, then blocks the entire machine whilst the disk access completes
- you can't even have
processes that are doing no disk I/O running during disk accesses.
Consequently, whilst Win3 does perform pre-emptive multitasking, it
is difficult to make adequate use of it. Win95 appears to have a
rather more rational filesystem and disk I/O subsystem.

- Raz rjturner@nospam.socs.uts.edu.au

"It often upsets a man's God fantasies to have (Misquoted? from )
someone shoot down one of his helicopters." (Ben Elton's "Stark" )