Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!usc!zaphod.mps.ohio-state.edu!think.com!linus!nixbur!nixpbe!ugun13!ugum01!josef From: josef@nixpbe.nixdorf.de (josef Moellers) Newsgroups: comp.os.msdos.misc Subject: Re: Multitasking? Message-ID: Date: 14 Dec 90 07:12:57 GMT References: <1990Dec13.033748.18606@CSUFresno.EDU> Sender: news@ugun13.UUCP Distribution: usa Lines: 35 In <1990Dec13.033748.18606@CSUFresno.EDU> brucen@CSUFresno.EDU (Bruce Nelson) writes: >I've heard alot about multitasking but not quite sure what true >multitasking is (according to IBM). >Is there anyone in netland that might be able to tell me what >"true" multitasking is, which microproccessors (8088, 80286, >80386sx, 80386, 80486) are able to multitask, and what type of >software allows multitasking. This sounds like the question about life and the reason for being B-{) I'll try and give an explanation about "multitasking": Simply stated, "multitasking" means that You can run "multi"ple "task"s more or less in parallel on a machine. A "task" being described not only by "physical" things like - a memory image (i.e. program code and it's data) - processor registers but also by "administrative" things like - task priority - access rights to various parts of the machine (HW & SW). This data is usually kept in a descriptor sometimes referred to as a "task descriptor block". The multitasking runtime system then "simply" switches between these descriptors thereby activating the tasks. I once implemented a simple multitasking system on a Z8. I.e. You can implement multitasking on just about every microprocessor, but You'll need more advanced processors to implement things like protection. Also these processors sometimes have special instructions to implement key features of multitasking, like task switching. -- | Josef Moellers | c/o Siemens Nixdorf Informationssysteme AG | | USA: mollers.pad@nixdorf.com | Abt. STO-XS 113 | | !USA: mollers.pad@nixdorf.de | Heinz-Nixdorf-Ring | | Phone: (+49) 5251 104662 | D-4790 Paderborn |