--- Don G skryf:

Of the mechanisms discussed, I am not sure I understand what you mean by async I/O with only one thread. I can imagine a nonblocking/select style approach that has no extra threads, but as soon as the main thread is not waiting on I/O itself (my interpretation of "async"), there needs to be threads to do the waiting.

The main thread does the waiting. In Windows NT you will either wait on the event flag in the OVERLAPPED structure or specify a completion routine and wait in an alertable state with the SleepEx or one of the *WaitFor*ObjectsEx functions. Groete Hans Malherbe ______________________________________________ "This information is intended only for the person or entity to which it is addressed and may contain private, confidential, proprietary and/or privileged material and may be subject to confidentiality agreements. Any review, retransmission, dissemination, or any other use of or taking of any action in reliance upon this information, by persons or entities other than the intended recipient, is prohibited. If you received this in error, please contact the sender and delete the material from all storage media. The company is neither liable for proper, complete transmission of the information contained in this communication, any delay in its receipt or that the mail is virus-free"