Virtual Machine (VM) in Computer Science

🔍 Basic Definition

A Virtual Machine (VM) is an emulated computer system that provides the functionality of a physical computer. It runs on a host machine and is managed by a hypervisor (also called a virtual machine monitor).

🧠 Key Concepts

Term	Explanation
Host Machine	The physical computer that provides resources (CPU, memory, storage) to run VMs.
Guest Machine	The virtual machine itself. It acts like an independent computer system.
Hypervisor	The software that creates and manages VMs. It allows multiple VMs to run on one physical system. Examples: VMware, VirtualBox, Hyper-V, KVM.
Virtualization	The process of creating a VM. It abstracts the hardware so multiple OS instances can run on one physical system.

🧰 What a VM Contains

Virtual CPU
Virtual Memory (RAM)
Virtual Hard Drive
Virtual Network Interface
Guest Operating System (e.g., Windows, Linux)

🔄 Types of Hypervisors

Type	Description	Example
Type 1 (Bare-metal)	Runs directly on hardware, without an underlying OS. Used in servers.	VMware ESXi, Microsoft Hyper-V, Xen
Type 2 (Hosted)	Runs on a host operating system. Easier for personal or development use.	VirtualBox, VMware Workstation

🧪 Common Uses of VMs

Testing new operating systems or software without affecting your main system
Running legacy applications that require old operating systems
Server virtualization in data centers to maximize hardware usage
Security sandboxing: isolating risky applications in a contained environment

✅ Advantages

Isolation between the host and guest systems
Easier system backups and snapshots
Cost-effective for running multiple servers

⚠️ Disadvantages

Some performance overhead
Resource-intensive (depends on hardware)