From: Michael J. Hußmann (michael_at_michael-hussmann.de)
Date: Mon Feb 23 2004 - 14:45:54 PST
Jared Bland (jrbm689_at_mac.com) wrote:
> BUT!!!:
> preemptive
>
> adj : designed or having the power to deter or prevent an anticipated
> situation or occurrence; "a preemptive business offer
In this context, "preemptive" means that the OS takes control over the
computer's resources: a process is granted use of the CPU for a certain
small amount of time, then the OS snatches the CPU from it and another
process may use the processor, and so on. No process can possibly
monopolize the CPU. Under a cooperative multitasking regime, it is really
the processes themselves that are in control: when a process decides it
may let the other processes play with the CPU for a while, it may do so,
but if it doesn't, then it has the computer all for itself. This is
generally considered to be a bad thing, and in most cases it is; on the
other hand, applications like Virtual PC did run much better under Mac OS
9, where they could monopolize the CPU while in the foreground, so this
behaviour was sometimes even useful.
Anyway, cooperative multitasking under System 7 (or with Multifinder
under System 6) was a huge improvement over previous versions of the Mac
OS. As was Apple events, AppleShare file sharing for everyone, TrueType
fonts, AppleScript, Drag&drop etc.. System 7 was a big step forward back then.
- Michael
Michael J. Hußmann
E-mail: michael_at_michael-hussmann.de
WWW (personal): http://michael-hussmann.de
WWW (professional): http://digicam-experts.de
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