On 12 Jul 2000, at 2:07, Dave Gillett wrote:
>   Win 9x, however, includes some core components which are still 16-
> bit code and which cannot safely/easily/efficiently be used by more
> than one app at a time.

To expand a bit...

Parts of the win9x User and GDI code are non re-entrant (some
actually 32 bit but mostly the older 16 bit).
A thread entering such code must obtain a mutex (a mutual
exclusion lock) that prevents other threads from entering the
same code. A 16 bit thread holds this mutex while running.

It is thus possible for a misbehaving 16 bit app to halt the user
interface threads of the 32 bit apps on the system since they
have to wait for the mutex to be released. This is the main reason
to use only 32 bit apps where possible.

Even with only 32 bit apps, a problem in the thread holding the
mutex will hang the other user interface threads.

Windows NT and W2K has no 16 bit code and all code is fully re-
entrant.



Gerard R Thomas
Port of Spain,  Trinidad and Tobago
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