## A

ACPI

  Advanced Configuration and Power Interface, an industry specification for BIOS and hardware extensions to configure PC hardware and perform power management. Windows 2000 and higher as well as Linux 2.4 and higher support ACPI. Windows can only enable or disable ACPI support at installation time.

AHCI

  Advanced Host Controller Interface, the interface that supports SATA devices such as hard disks. See .

AMD-V

  The hardware virtualization features built into modern AMD processors. See .

API

  Application Programming Interface.

APIC

  Advanced Programmable Interrupt Controller, a newer version of the original PC PIC (programmable interrupt controller). Most modern CPUs contain an on-chip APIC ("local APIC"). Many systems also contain an I/O APIC (input output APIC) as a separate chip which provides more than 16 IRQs. Windows 2000 and higher use a different kernel if they detect an I/O APIC during installation. Therefore an I/O APIC must not be removed after installation.

ATA

  Advanced Technology Attachment, an industry standard for hard disk interfaces (synonymous with IDE). See .

## B

BIOS

  Basic Input/Output System, the firmware built into most personal computers which is responsible of initializing the hardware after the computer has been turned on and then booting an operating system. VirtualBox ships with its own virtual BIOS that runs when a virtual machine is started.

## C

COM

  Microsoft Component Object Model, a programming infrastructure for modular software. COM allows applications to provide application programming interfaces which can be accessed from various other programming languages and applications. VirtualBox makes use of COM both internally and externally to provide a comprehensive API to 3rd party developers.

## D

DHCP

  Dynamic Host Configuration Protocol. This allows a networking device in a network to acquire its IP address (and other networking details) automatically, in order to avoid having to configure all devices in a network with fixed IP addresses. VirtualBox has a built-in DHCP server that delivers an IP addresses to a virtual machine when networking is configured to NAT; see .

DKMS

  Dynamic Kernel Module Support. A framework that simplifies installing and updating external kernel modules on Linux machines; see .

## E

EFI

  Extensible Firmware Interface, a firmware built into computers which is designed to replace the aging BIOS. Originally designed by Intel, most modern operating systems can now boot on computers which have EFI instead of a BIOS built into them; see .

EHCI

  Enhanced Host Controller Interface, the interface that implements the USB 2.0 standard.

## G

GUI

  Graphical User Interface. Commonly used as an antonym to a "command line interface", in the context of VirtualBox, we sometimes refer to the main graphical `VirtualBox` program as the "GUI", to differentiate it from the `VBoxManage` interface.

GUID

  See UUID.

## I

IDE

  Integrated Drive Electronics, an industry standard for hard disk interfaces. See .

I/O APIC

  See APIC.

iSCSI

  Internet SCSI; see .

## M

MAC

  Media Access Control, a part of an Ethernet network card. A MAC address is a 6-byte number which identifies a network card. It is typically written in hexadecimal notation where the bytes are separated by colons, such as `00:17:3A:5E:CB:08`.

MSI

  Message Signalled Interrupts, as supported by modern chipsets such as the ICH9; see . As opposed to traditional pin-based interrupts, with MSI, a small amount of data can accompany the actual interrupt message. This reduces the amount of hardware pins required, allows for more interrupts and better performance.

## N

NAT

  Network Address Translation. A technique to share networking interfaces by which an interface modifies the source and/or target IP addresses of network packets according to specific rules. Commonly employed by routers and firewalls to shield an internal network from the Internet, VirtualBox can use NAT to easily share a host's physical networking hardware with its virtual machines. See .

## O

OVF

  Open Virtualization Format, a cross-platform industry standard to exchange virtual appliances between virtualization products; see .

## P

PAE

  Physical Address Extension. This allows accessing more than 4 GB of RAM even in 32-bit environments; see .

PIC

  See APIC.

PXE

  Preboot Execution Environment, an industry standard for booting PC systems from remote network locations. It includes DHCP for IP configuration and TFTP for file transfer. Using UNDI, a hardware independent driver stack for accessing the network card from bootstrap code is available.

## R

RDP

  Remote Desktop Protocol, a protocol developed by Microsoft as an extension to the ITU T.128 and T.124 video conferencing protocol. With RDP, a PC system can be controlled from a remote location using a network connection over which data is transferred in both directions. Typically graphics updates and audio are sent from the remote machine and keyboard and mouse input events are sent from the client. A VirtualBox extension package by Oracle provides VRDP, an enhanced implementation of the relevant standards which is largely compatible with Microsoft's RDP implementation. See for details.

## S

SAS

  Serial Attached SCSI, an industry standard for hard disk interfaces. See .

SATA

  Serial ATA, an industry standard for hard disk interfaces. See .

SCSI

  Small Computer System Interface. An industry standard for data transfer between devices, especially for storage. See .

SMP

  Symmetrical Multiprocessing, meaning that the resources of a computer are shared between several processors. These can either be several processor chips or, as is more common with modern hardware, multiple CPU cores in one processor.

## T

TAR

  A widely used file format for archiving. Originally, this stood for "Tape ARchive" and was already supported by very early Unix versions for backing up data on tape. The file format is still widely used today, for example, with OVF archives (with an `.ova` file extension); see .

## U

UUID

  A Universally Unique Identifier -- often also called GUID (Globally Unique Identifier) -- is a string of numbers and letters which can be computed dynamically and is guaranteed to be unique. Generally, it is used as a global handle to identify entities. VirtualBox makes use of UUIDs to identify VMs, Virtual Disk Images (VDI files) and other entities.

## V

VM

  Virtual Machine -- a virtual computer that VirtualBox allows you to run on top of your actual hardware. See for details.

VMM

  Virtual Machine Manager -- the component of VirtualBox that controls VM execution. See for a list of VirtualBox components.

VRDE

  VirtualBox Remote Desktop Extension. This interface is built into VirtualBox to allow VirtualBox extension packages to supply remote access to virtual machines. A VirtualBox extension package by Oracle provides VRDP support; see for details.

VRDP

  See RDP.

VT-x

  The hardware virtualization features built into modern Intel processors. See .

## X

XML

  The eXtensible Markup Language, a metastandard for all kinds of textual information. XML only specifies how data in the document is organized generally and does not prescribe how to semantically organize content.

XPCOM

  Mozilla Cross Platform Component Object Model, a programming infrastructure developed by the Mozilla browser project which is similar to Microsoft COM and allows applications to provide a modular programming interface. VirtualBox makes use of XPCOM on Linux both internally and externally to provide a comprehensive API to third-party developers.