Talk:Computer multitasking
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Removed: "UNIX, designed as a "single user" operating system in the 1970s, included most of the multitasking capabilities of its multi-user cousin MULTIX, and is today used for both purposes." Bad example because it is mostly untrue. Unix was very briefly a single user system, but got both multi-user and multi-tasking features very early, and at about the same time.
- Perhaps we could find a better example of multitasking being recognized as a useful feature even in a single user OS, such as a PC OS? Paragraph 8 ("Although the original purpose behind the design...") would be a good place for it. --D
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"To remedy this situation, most time-sharing systems quickly evolved a more advanced approach known as [preemptive multitasking]?. "
In context, this reads like preemptive multitasking developed after cooperative multitasking. Preemptive multitasking was tried in the early 1960s, but it turned out to be a lot harder to do reliably than anyone expected. Remember that back then, people routinely made I/O calls from applications and grabbing control away from somebody who had just issued a read to a paper tape reader often didn't work out all that well. I'm pretty sure that cooperative multitasking was a kludge to make multitasking work better by making sure that programs were in a suspendable state when they gave up control.
I'm not sure, however, whether a change is needed or will be an improvement. - DJK
multitasking vs multiprogramming vs time sharing
It seems those three notions are intermixed here. A clarification is needed.
- Multitasking is a generic term allowing multiple tasks to be run, witout regard to timing.
- Multiprogramming is the possibility for multiple programs to be ready, and waiting for the processor to be free. The initial purpose of this was to allow a second program to run while the first one waited for some I/O to complete. Multiprogramming does not require any cooperation between programs, as there were no interactive users anyway. If a program needed the CPU for a long time, it could use it.
- Time sharing is a method where all ready tasks are given a fair access to the CPU.
The goal of multiprogramming is to minimize idle time for the processor, and that was the primary objective in the times the processor time was expensive.
reading from a tape
"(e.g. reading from a tape)" ?? Dated? In a modern computer would this be comparable to reading from a drive or waiting for a result from memory or an external device? - Omegatron 18:06, Oct 13, 2004 (UTC)