Use of virtual machine environment question

February 9, 2011 at 03:17:52
Specs: Windows XP pro, 1,6 / 724
my question :

the virtual machine environnement is it used to interpreter program ?
on wich layer is it loaded ?.

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February 9, 2011 at 03:40:13
It depends on the virtual machine referred. MS Virtual PC is a Virtualizer, i.e. it executes the non-privileged instructions while traps the inner layer commands to virtualize I(O interactions and OS services. Open Source Bochs is an Emulator that interprets the whole code so enabling a Intel compiled program to be executed on other platform.

As far as I know all virtual machines run as user applications without special privileges

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February 10, 2011 at 04:50:26
then they are here just to control user mode application (without privelige), when we are user of computer it's usuaful for us to control our machine... what you think,
dont tell me the virtual environnement is there to simplicitizing the task of user programm (abstraction of other thing),,, but analizing by a way, (all stuff of spyring (collecting user data) is provided by this level, (the complexite of the dependecing and encabsulation of different system object...), and the non-distribut information about this (else by own guess...);;;;

how do sow this...

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February 10, 2011 at 08:41:52
Well, I admit I don't clearly understand what you are lookiing for...

Virtual environments offered by virtual machines are mainly oriented to allow running an operating system as guest of the host driving the real computer.

This process has different levels of complexity depending on the environments targeted. You may want to run a mainframe OS and its applications on a PC or just run two Intel based OS concurrently. In the first case you need to emulate the lowest layer of the software interfaces (the machine code to firmware) while in the second case you need just to trap system calls.

Hercules emulator allows to run IBM S/390 system softwsre on Intel platforms under Windows or Linux while MS Virtual PC Virtualizer runs e.g. DOS and XP concurrently. Obviously complexity is hgher for Hercules. There are virtual environments with builtin OS emulation too, e.g. DOSbox.

How and why to use virtual machines depends on the purposes of the user (security issues, porting problems, revamping legacy software) since virtual machines are system software to be tailored according to users' purposes.

This is just a short note since the item is deep as Ocean.

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February 10, 2011 at 17:11:11
all this stuff (xen, bochs, virtualpc, vmware, kvm, qemu, .... in progress) finaly dose the same work (same concept and it's can be supervisor or hypervisor).

can we just say a "vm" help a program to be excecuted on different machine or system . . . .

in conclusion a vm (see also pvm) is an Interpreter : dosnt it ?

direct question : on xp architecture : where is the VM ?

- in user mode : integral or environment;
- in executive (......)
- in kernel mode : kernel mode drivers or microkernel
- in hal layer.

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February 11, 2011 at 02:20:42
At the dawn of electronic computers (early '50) the lowest level of "software" was binry machine code that switched directly logic gates. The introduction of chipsets heralded the eve of "microcode" that took away the design stage of a system from its underlaying architecture. IBM S/360 in 1964 was the first example of this system engineering. The first virtual machine (excluding Turing's emulator) was just planned on a 360 mainframe: CP/67 then VM/370. A virtual machine operates at software level what is done by the binary code -microprogram interface in all modern system.

Interpreter is bound to programming languages translation and so it rawly applies to virtual machine operations, it is much as to say the Space Shuttle is an airplane, however that may be said. In short words, yes, a virtual machine "enables" to execute programs designed to run on different architectures.

In XP there is a builtin virtual machine to enable legacy DOS applications, NTVDM (NT Virtual DOS Machine aka the 16 bit subsystem) but if you refer to XP system architecture I guess you may say the vm is the hal layer.

About this nowever be aware the opinion may be different depending on point of view.

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February 11, 2011 at 05:30:10
and now we are on same hz;

the first thechnologie of VM that adobted by IBM ( see now the z10 ) is dedicated to emulate hardware.

the same concept to emulate some thing for some thing.

then on windows mainframe x86: the VM is to prepare data and code that is needed by an program.

i guess there is a big difference betwen the oriented technologie of VM and the microsoft VM. also, it is a pur market technique.

what do you think.

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February 11, 2011 at 07:20:59
Sorry, I disagree on your opinion about historycal IBM VM/370 and today virtual machines running on PCs.

On a IBM system 370 you could run DOS/VS or MVS or both concurrently when installed VM/370. It was pure software allowing to execute programs compiled for DOS/VS while operating under MVS environment. Without any hardware device added to the system. I personally managed that when young thirty years ago.

Today on your X86 PC you can run Windows (maybe DOS) or Linux or both concurrently after installing a virtual environment as Virtual PC, VirtualBox or VMWare (whose name remembers the ancestor IBM VM). That without plugging in any additional card or device.

There is one fundamental difference: VM/370 is a Hypervisor while virtual machines are convedntional (but complex) user applications. I.e. a Hypervisor is a software layer under operating system(s) that monitors the slave supervisors (for VM/370 DOS/VS and MVS - and a customized software for airlines management).

Virtual machines lie to the guest OS that thinks to be the master of the computer. Open Source Xen and VMWare Enterprise environments are more similar to Hypervisor. So to be short a Hypervisor is system software while virtual machines run system software but are plain applicatioins.

Then there are Emulators, i.e. something that mimics something else. DOSbox is an emulator, it doesn't run system software, just executes programs compiled under MS DOS. In the jurassic eve of computers IBM had emulators to run 7094 programs on S/360 mainframes.

So to summarize:

Hypervisor --> Operating Systems --> Applications
Operating System --> Virtual Machine --> [guest] Operating System --> Apps
Operating System --> Emulator --> [guest] Application

All above belongs to the realm of software (system or application). To end let me post a personal note: in 1973 I awarded my engineering doctorate by lecturing on "Description and Emulation of Computer Architectures: the SLANG Language".

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February 11, 2011 at 11:03:00
i see and absolotly agree with you,

then ; you perfectly know that technique is a big/complex concept . . .

peacful and sincerly apreciate. thinks

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February 11, 2011 at 13:35:48
Thanks for your feedback. Just curious, why are you so interested to these issues?

Usually people want the beeef and do not care a lot about the desk.

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February 11, 2011 at 15:18:03
to answer you i'll tell a story, in secondary scool, i have 14-15 years old, the teacher ask us to prepare some thing (an initiative home work), every body was selecting some usual thing, i said to him, i give you a robot, and he said : " wwwhat !, are you jooking ".

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February 12, 2011 at 02:52:37
...And did you make the robot?

This sounds like a story to be continued and more I am a sci-fi fan too interested to robots, cyborgs and artificial intelligence (almost from a fiction point of view).

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February 12, 2011 at 04:49:10
i buil a wood-hand with three finger . . . and he mark me 18/20,

You Know what, i believe in humain intelligency...
and the stories that we sow in sci-fic movie become real,

i believe that we can now build real robot .
the neural network concept can play some roll in this..
and some multi-core.. and more

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