E

EA

Extended attribute. An EA is viewed as an untyped name-value pair that is defined by the user to describe extended information about a file. Typical system uses are to store the icon for an image, to indicate that the file is a symbolic link, and so on.

ECC

Error correction code.

ECP

Extended capabilities port. An asynchronous, 8-bit-wide parallel channel defined by IEEE 1284—1944. This channel provides PC-to-peripheral and peripheral-to-PC data transfers.

EISA

Extended industry standard architecture. A standard that defines the architecture of (and interface to) the extended PC I/O bus.

See also ISA.

electronic program guide (EPG)

The on-screen user interface that allows users to select, manage, and search television programs and other content-viewing options.

engine-managed surface

A device-independent bitmap (DIB) that is created and managed by GDI. GDI can handle any or all drawing operations for the surface. For a surface to be engine-managed, it must be a DIB.

For more information, see the topic Surface Types.

enhanced metafile (EMF)

A type of spool file used by print spoolers on NT-based operating systems. An EMF reduces the time it takes for control to be returned to an application that makes a print request. The GDI function calls that produce the application's graphics object are stored directly in the EMF. The time-consuming execution of these stored GDI functions is carried out later, in the background, when the spool file is played back.

Using EMF spool files also promotes printer device independence. For example, a picture that measures 2 inches by 4 inches on a VGA display and that is stored in an EMF maintains these original dimensions, regardless of the printer's resolution.

enumerator

A system component that discovers PnP devices based on a PnP hardware standard. For Windows 2000 and later, these tasks are carried out by PnP bus drivers in partnership with the PnP Manager. A device is typically enumerated by its parent bus driver, such as the PCI or PCMCIA bus driver. Some devices are enumerated by a bus filter driver, such as the ACPI driver.

ESS

See Extended Service Set.

event object

A user-mode object upon which one or more threads can wait until the event is set to the Signaled state. Every user-mode event object is implemented through the use of a kernel-mode event object. A kernel-mode event object is an instance of a kernel-defined dispatcher object type.

Each event object can be classified as either of the following:

• When a synchronization event (also called an autoclearing event) is set to the Signaled state, a single thread that was waiting on the event is released (its dispatch state makes a transition from waiting to ready, standby, or running), and the event is automatically reset to the Not-Signaled state.
• When a notification event is set to the Signaled state, all threads that were waiting on the event are released, and the event remains in the Signaled state until it is explicitly reset to the Not-Signaled state.

event set

A uniquely identified set that represents a group of items about which a client can be notified.

exception

A synchronous error condition that results from the execution of a particular machine instruction.

See also structured exception handling.

exclusive device

A device for which only one handle can be open at a time. For more information, see Specifying Exclusive Access to Device Objects.

executive

The collection of kernel-mode components that form the NT-based operating system. Executive components include executive support, the kernel, the Memory Manager, the Cache Manager, process structure, interprocess communication (LPC and RPC), the Object Manager, the I/O Manager, the Configuration Manager, the hardware abstraction layer (HAL), and the Security Reference Monitor. Each executive component, with the exception of the Cache Manager and the HAL, supplies a specialized set of native system services. Every executive component also exports a set of kernel-mode support routines for use by other executive components.

Kernel-mode drivers also call kernel-mode support routines supplied by executive components, including (but not limited to) routines beginning with the prefix "Ex" for Ex(ecutive) Support. Other support routines of interest to drivers begin with the prefixes Ke(rnel), Po (for Power), Ps (for Process Structure), Ob(ject), Io (for I/O Manager), Mm (for Memory Manager), Se(curity Manager), Rtl (Run-Time Library), and FsRtl (for File System Run-Time Library).

Note that drivers, including device, intermediate, and file system drivers, are considered part of the executive after they are loaded. The "operating system" visible to end users is actually a protected subsystem that runs in user mode on top of the executive, and calls system services. That is, the executive is hidden from end users by a subsystem-supplied interface that emulates Windows®, POSIX, or some other operating system.

See also Zw routines.

executive worker threads

See system worker threads.

extended display identification data (EDID)

A format that lets the display supply the host with information about its identity and capabilities independent of the communications protocol used between the monitor and host.

Extended Service Set (ESS)

A complete 802.11 wireless network. An ESS is composed of different base service sets and their respective access points, as well as the distribution system. An ESS appears to be a single 802 network to the upper layers of the OSI model.