I

I picture

Intra-coded picture. A picture type that is coded as a stand-alone image. It does not use motion-compensated prediction.

I/O control code

See IOCTL.

IA44

Index-Alpha 4-4. A video surface subtype used by decoders that implement DirectX® VA. IA44 has a bits-per-pixel value of 8. The character "I" is a 4-bit index into a 16-entry YUV palette. The character "A" represents 4 bits of transparency information (also known as per-pixel alpha). An IA44 surface allows for 16 different colors at 16 different transparency values, or 256 different pixel representations. In IA44 the alpha is stored in the low-nibble.

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.

IDB

Interrupt dispatch block. An internal structure used by the kernel.

IDCT

Inverse Discrete Cosine Transform. A method to convert macroblocks of DCT coefficients back to pixels. IDCT reverses the DCT process.See also DCT

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.

IDT

Interrupt dispatch table. A kernel-defined call table with a platform-dependent number of first-level entries (some for DIRQL ISRs) and second-level entries for interrupt transfer routines (dependent on a first-level ISR). For symmetric multiprocessor platforms, the kernel sets up an IDT for each processor.

The kernel reserves eight first-level entries per IDT for its own use; the remaining first-level entries can be connected to a platform-specific I/O bus interrupt by the HAL or to a device interrupt. The kernel’s reserved entries (in low-to-high IRQL priority) are defined by the following constants:

• PASSIVE_LEVEL – execute thread
• APC_LEVEL – execute special kernel APC; page fault
• DISPATCH_LEVEL – dispatch (execute DPC)
• WAKE_LEVEL – debugger execution
• CLOCK2_LEVEL – interval-timer execution
• REQUEST_LEVEL – interprocessor request
• POWER_LEVEL – power failure notification
• HIGH_LEVEL – machine checks or bus errors

The set of software and hardware interrupt vectors mapped to these constants is platform-dependent, but none can be connected to a driver's interrupt object. Note that the constants PASSIVE_LEVEL through DISPATCH_LEVEL and WAKE_LEVEL correspond to software interrupt vectors. DIRQLs for device drivers usually have hardware priority higher than DISPATCH_LEVEL but lower than CLOCK2_LEVEL.

See also multiprocessor machine.

IEEE 1284 Bidirectional Parallel Peripheral Interface

An interface standard that adds bidirectional communication capabilities to a peripheral device that is connected to a computer’s parallel port.

IETF

Internet Engineering Task Force.

IFS

Installable file system. See FS.

image color management (ICM)

A technology developed by Microsoft that ensures that a color image, graphic or text object is rendered as close as possible to its original intent on any device, despite differences in imaging technologies and color capabilities between devices.

independent configuration

See ad hoc mode.

independent hardware vendor (IHV)

A third-party hardware vendor.

independent software vendor (ISV)

A third-party software vendor.

INF File

A text-based file containing information required by the system to install a device's software components.

For more information see the topic, Creating an INF File.

infrastructure configuration

An infrastructure configuration is an 802.11 LAN configuration that makes it possible for stations to communicate with access points. The access points communicate through portals that are part of a distribution system. Each access point serves the stations in a Basic Service Set (BSS), and the set of BSSs defines an Extended Service Set (ESS).

INI file

An initialization file. Commonly used in 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 later Windows operating systems, INI files are supported for backward compatibility, but the registry is the preferred location for storing such settings.