begin Michael Wenk <[EMAIL PROTECTED]> > On Monday 31 March 2003 12:39 pm, Peter Jay Salzman wrote: > > can someone tell me if this is a formally correct explanation of what a > > virtual machine is? > > > > pete > > > > > > A "real computer" provides an operating system many things, including a > > CPU, I/O channels, memory, a BIOS to provide low level access to > > motherboard and I/O resources, etc. When an operating system wants to > > write to a hard drive, it communicates through a device driver that > > interfaces directly with the hardware device memory. > > > > However, it's possible to give a program all the hardware resources it > > needs. When it wants to access a hard drive, give it some memory to > > write to. When it wants to set an IRQ, give it some bogus instructions > > that lets it think it set an IRQ. If you do this correctly, then in > > principle, there's no way for the application to know whether it's > > really accessing hardware or tricked by being given resources which > > simulate hardware. A virtual machine is the environment which tricks > > applications into believing they're running on a real computer. It > > provides all the services that a real computer would provide. > > > > VM's were used initially in the 1960's to emulate time shared operating > > systems, but these days we use them to run software which was written > > for foreign operating systems, or more commonly, an entire operating > > system. Because of the nature of the VM, the foreign OS can't tell the > > difference between operating in a VM or in a "real" machine. > > _______________________________________________ > > vox-tech mailing list > > [EMAIL PROTECTED] > > http://lists.lugod.org/mailman/listinfo/vox-tech > > > Well, I can't find my old CS book, but I prefer the Java definition for a > VM: > > "An abstract specification for a computing device that can be implemented in > different ways, in software or hardware. ..." > > It goes on to more java and jvm specific information. I think the > important keyword is abstract. You're definition is more specific, but > a VM can describe just about any computing device, and arguably > every computing device may not have the components you listed. > > Mike
unfortunately, that definition doesn't really talk to me. :( pete -- Fingerprint: B9F1 6CF3 47C4 7CD8 D33E 70A9 A3B9 1945 67EA 951D _______________________________________________ vox-tech mailing list [EMAIL PROTECTED] http://lists.lugod.org/mailman/listinfo/vox-tech
