I

I2O

Intelligent I/O.

IA-PC

Intel Architecture Personal Computer. A general descriptive term for computers built with processors conforming to the architecture defined by the Intel processor family based on the 486 instruction set and having an industry-standard PC architecture.

ICD

Installable Client Driver. An OpenGL driver model in which the driver is responsible for implementing the entire OpenGL pipeline. Intended for high-end graphics cards that implement most of the OpenGL pipeline in hardware.

IDE

Integrated Device Electronics. A type of disk-drive interface where the controller electronics reside on the drive itself, eliminating the need for a separate adapter card.

IEEE

Institute of Electrical and Electronics Engineers. Organization that developed the IEEE 802 standards, among others, for the physical and data-link layers of LANs following the ISO/OSI model.

IETF

Internet Engineering Task Force.

IHV

Independent hardware vendor.

image

The computerized representation of a picture or graphic.

image resolution

The fineness or coarseness of an image as it is digitized; measured in dots per inch (DPI), typically ranging from 200 to 400 DPI.

in

In terms of data flow, indicates consumption of data. An in pin is compatible with an out pin.

INF file

Information file. A file created for a particular adapter that provides the operating system with information required to set up a device, such as a list of valid logical configurations for the device, the names of driver files associated with the device, and so on. An INF file is typically provided by the device manufacturer on a disk with an adapter.

INI file

Initialization file. Commonly used under Windows 3.x and earlier, INI files have been used by both the operating system and individual applications to store persistent settings related to an application, driver, or piece of hardware. In Windows NT/Windows 2000 and Windows 95, INI files are supported for backward compatibility, but the registry is the preferred location for storing such settings.

input class

The class of filters that provide an interface for HID hardware, including USB and legacy devices, plus proprietary and other HID hardware, under the WDM HID architecture.

instantiate

In object-oriented programming, to create an instance of a class.

instrumentation

A mechanism for reporting information about the state of PC hardware and software to enable management applications to ascertain and change the state of a PC and to be notified of state changes.

integrated device

Any device—such as a parallel port, graphics adapter, and so on—that is designed on the system board rather than on an expansion card.

interactive video

A video program and a computer program running in tandem under the control of the user. In interactive video, the user's actions, choices, and decisions genuinely affect the way in which the program unfolds.

interface

For parameters on a connection request, a specific set of methods and properties implemented on a medium that a filter connection uses to communicate, such as a specific set of IOCTLs.

interframe coding

Compression techniques that track the differences between frames of video. This results in more compression over a range of frames than intraframe coding.

interlaced

1. A scanning method that divides the screen into two fields, alternately drawing odd-numbered and even-numbered scan lines. 2. A scheme to display a video image by displaying alternate scan lines in two discrete fields. Interlaced signals are used in broadcast video and are required for video to be compliant with NTSC.

interpolation

The process of averaging pixel information when scaling an image. When reducing the size of an image, pixels are averaged to create a single new pixel; when an image is scaled up in size, additional pixels are created by averaging pixels of the smaller image.

intraframe coding

Compression within each frame individually. This results in less compression over a range of frames than interframe coding.

I/O

Input/output. Two of the three activities that characterize a computer (input, processing, and output). Refers to the complementary tasks of gathering data for the microprocessor to work with and make the results available to the user through a device such as the display, disk drive, or printer.

IOCTL

Input/output control. A custom class of IRPs available to User mode. Each WDM class driver has a set of IOCTLs that it uses to communicate with applications. The IOCTLs give the class driver information about intended usage by applications. The class driver performs all IOCTL parameter validation.

IPL

Initial program load. A device used by the system during the boot process to load an operating system into memory.

IrDA

Infrared Data Association.

IRP

I/O request packet. Data structures that drivers use to communicate with each other. The basic method of communication between kernel-mode devices. An IRP is a key data structure for WDM, which features multiple layered drivers. In WDM, every I/O request is represented by an IRP that is passed from one driver layer to another until the request is complete. When a driver receives an IRP, it performs the operation the IRP specifies, and then either passes the IRP back to the I/O Manager for disposal or onto an adjacent driver layer. An IRP packet consists of two parts: a header and the I/O stack locations.

IRP_MJ_XXX

IRP Major. One of a predefined class of IRPs that a device can accept.

IRQ

Interrupt request. A method by which a device can request to be serviced by the device's software driver. The system board uses a PIC to monitor the priority of the requests from all devices. When a request occurs, the microprocessor suspends the current operation and gives control to the device driver associated with the interrupt number issued. The lower the number—for example, IRQ3—the higher the priority of the interrupt. Many devices only support raising requests of specific numbers.

ISA

Industry Standard Architecture. An 8-bit (and later, a 16-bit) expansion bus that provides a buffered interface from devices on expansion cards to the PC internal bus.

ISDN

Integrated Service Digital Network. A set of communications standards that enable a single phone line or optical cable to carry voice, digital network services, and video.

ISO

International Standards Organization.

isochronous

Refers to a communication protocol based on time slices rather than handshaking. For example, a process might have 20 percent of total bus bandwidth. During its time slice, the process can stream data.

isolation

The Plug and Play process by which cards on an ISA bus are distinguished from each other after system startup.

ISO/OSI

International Standards Organization Open Systems Interconnection model. A layered architecture that standardizes levels of service and types of interaction for computers exchanging information through a communications network.

ISR

Interrupt service routine. A routine whose function is to service a device when it generates an interrupt.