This document provides an overview of virtual machines, including their history, types (system and process virtual machines), and benefits such as scalability and easy cloning. It explains how virtual machines simulate hardware environments to allow multiple operating systems to run concurrently and highlights challenges in their implementation. Examples of virtual machines include VMware, the Java Virtual Machine, and the .NET Framework.

1. VIRTUAL MACHINE
Presented By : Prakhar Maurya
B.Sc. IT (3rd Semester)
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2. Contents :
• History
• Introduction of Virtual Machine
• Types of Virtual Machine
• Benefits
• Simulation
• Implementation
• Examples
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3. History :
Virtual machines first appeared as the VM Operating
system for IBM mainframes in 1972.
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4. Introduction :
The virtual machine
provides an interface that is identical to
the underlying bare hardware. Each
process is provided with a (virtual)
copy of the underlying computer.
Usually, the guest process is in fact an
operating system, and that is how a
single physical machine can run
multiple operating systems
concurrently, each in its own virtual
machine.
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5. Types of VM :
• System Virtual Machine
• Process Virtual Machine
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6. System Virtual System :
System virtual machine (also
known as hardware virtual machine). The system VM
simulates the complete system hardware stack and
support the execution of complete operating system.
Process Virtual System :
Process virtual machine (also
known as application virtual machine). Process VM adds up
layer over an operating system which is use to simulate the
programming environment for the execution of individual
process.
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7. Benefits :
• Familiar Interfaces
• High Availability
• Scalability
• Backup and Fast Recovery
• Easy Cloning
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8. Simulation :
An alternative to creating an entire virtual
machine is to simply run an emulator, which allows a program
written for one OS to run on a different OS. For example, a
UNIX machine may run a DOS emulator in order to run DOS
programs, or vice-versa. Emulators tend to run considerably
slower than the native OS, and are also generally less than
perfect.
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9. Implementation :
Implementation may be challenging,
partially due to the consequences of user versus kernel mode.
Each of the simultaneously running kernels needs to operate in
kernel mode at some point, but the virtual machine actually
runs in user mode. So the kernel mode has to be simulated for
each of the loaded Operating Systems, and kernel system calls
passed through the virtual machine into a true kernel mode for
eventual hardware access. The virtual machines may run
slower, due to the increased levels of code between
applications and the hardware, or they may run faster, due to
the benefits of caching.
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10. Examples :
• VMware : VMware is desktop software runs on Microsoft Windows, Linux,
and Mac OS X, while its enterprise software hypervisors for servers, VMware
ESX and VMware ESXi, are bare-metal hypervisors that run directly
on server hardware without requiring an additional underlying operating
system.
• The JAVA Virtual Machine
• The .NET Framework
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11. Thank You…..
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