Io Multiplexing

I/O multiplexing means what it says - allowing the programmer to examine and block on multiple I/O streams (or other "synchronizing" events), being notified whenever any one of the streams is active so that it can process data on that stream.

In the Unix world, it's called select() or poll() (when using the CeeLanguage API for Unix). In the MicrosoftWindowsApi world, it's called WaitForMultipleObjects?(). Other languages/environments have similar features:

The advantage of IoMultiplexing is that it allows blocking on multiple resources simultaneously, without needing to use polling (which wastes CPU cycles) or multithreading (which can be difficult to deal with, especially if threads are introduced into an otherwise sequential app only for the purpose of pending on multiple descriptors).

With the understanding, of course, that the CPU cycles are gonna get burned somewhere anyway, and even if your task/process is not threaded, the system as a whole will have other threads/tasks running.

• Agreed; with the caveat that there is a lot of difference between CPU cycles spent polling (even if it's a test-then-sleep loop) and CPU cycles spent doing productive work. OTOH, on many destkop systems most CPU cycles are spent in the IdleTask.