Hi! > In creating a multi-tasking dos,, why doesn't someone > just create a version of dos which spawns a whole new > virtual 386 machine for each application that is launched > at the command line?
Windows 3 does this for each DOS window you open. The complicated part is making the already loaded parts of DOS including the kernel believe that only one app is running. You have to save and restore state, e.g. SDA. The kernel still only handles 1 request at a time, but that is acceptable when most CPU time is spent in apps. You also have to take care that different apps do not try to access the same files, as the state swapping hides things happening in each task from each other. The different tasks also cannot communicate with each other using DOS, but they can communicate with Windows if they know how to do that. > I think the software vmix386 Does it work with freedos? Which license does it have? Did you try tridos, by the way? It does similar stuff but not fully using protected mode afair, just swaps all DOS memory into chunks of XMS or similar memory? Making all this cooperate with HIMEM / EMM386 also adds complexity, as does allowing the DOS apps to access hardware directly. Many apps access e.g. the screen, so you have to simulate N virtual screens and somehow display one or more of them on the actual VGA screen. Remember how Windows supported less and less graphics for DOS over time, as they wanted to simplify things. > Is this what windows attempted to do with it enhanced 386 mode? > If so, why did it work so badly? How badly did it work? It does not work well in FreeDOS, you need to use the experimental winkern patches there because of the very lowlevel approach of state swapping. Windows 3 in standard mode swaps in more harmless ways. Eric ------------------------------------------------------------------------------ Create and Deploy Rich Internet Apps outside the browser with Adobe(R)AIR(TM) software. With Adobe AIR, Ajax developers can use existing skills and code to build responsive, highly engaging applications that combine the power of local resources and data with the reach of the web. Download the Adobe AIR SDK and Ajax docs to start building applications today-http://p.sf.net/sfu/adobe-com _______________________________________________ Freedos-user mailing list Freedos-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/freedos-user
