S

sampling

The first step in the process of converting an analog signal into a digital representation. Accomplished by measuring the value of the analog signal at regular intervals (called samples). These values are then encoded to provide a digital representation of the analog signal.

saturation

The extremes of operating range wherein the output is constant, regardless of changes in input.

scalability

The ability to vary the information content of a program by changing the amount of data that is stored, transmitted, or displayed. In a video image, this translates to creating larger or smaller windows of video on screen (shrinking effect).

scaling

Process of uniformly changing the size of characters or graphics.

SCAM

SCSI Configured Automatically.

SCI

System control interrupt. A system interrupt used by hardware to notify the operating system of ACPI events. The SCI is an active low, shareable, level interrupt.

SCSI

Small computer system interface. Pronounced "scuzzy." An I/O bus designed as a method for connecting several classes of peripherals to a host system without requiring modifications to generic hardware and software.

SDK

Software development kit.

SECAM

Sequential Couleur a Memoire (Sequential Color with Memory). The television standard for France, Russia, and most of Eastern Europe. As with PAL, SECAM is based on a 50-Hz power system, but it uses a different encoding process and displays 819 horizontal lines per frame at a scan rate of 25 frames per second (50 fields per second). See also NTSC and PAL format.

sequencer

Hardware or software functionality that interprets a time-stamped music data stream and sends packets to music hardware as their time comes due.

sink

In terms of device stacking in ActiveMovie, indicates that a pin represents possible connections that are attached to, rather than those that attach. Compare with source.

SIPC

Simply Interactive PC. A vision guiding investments that Microsoft is making in software and hardware advances to make the PC as simple, convenient, and approachable as an appliance.

Smart Battery subsystem

A battery subsystem that conforms to the ACPI requirements and implementation defined in Smart Battery Charger Specification and related specifications.

Smart Battery table

An ACPI table used on platforms that have a Smart Battery subsystem. This table indicates the energy level trip points that the platform requires for placing the system into different sleeping states, plus suggested energy levels for warning the user to transition the platform into a sleeping state.

SMBus

A two-wire interface based on the I²C protocol. The SMBus is a low-speed bus that provides positive addressing for devices, as well as bus arbitration.

SMBus interface

ACPI defines a standard hardware and software communications interface between an operating system bus driver and an SMBus controller using an embedded controller.

SMI

System management interrupt. An operating-system–transparent interrupt generated by interrupt events on legacy systems. By contrast, on ACPI systems, interrupt events generate an operating-system–visible interrupt that is shareable (edge-style interrupts will not work).

SMPTE timecode

An 80-bit standardized edit time code adopted by the Society of Motion Picture and Television Engineers. See timecode.

SMS

1) Microsoft Systems Management Server. Provides a centralized management service for distributed systems. 2) Short messaging service.

socket services

In Windows, a protected-mode VxD that manages PC Card hardware. Provides a protected-mode PCMCIA Socket Services 2.x interface for use by Card Services. A socket-services driver must be implemented for each separate PC Card controller that is used.

software device

A filter in kernel streaming and ActiveMovie that has no underlying hardware associated with it.

software modem

Also host-based signal processing or pumpless modem. Performs signal processing on the host CPU and implements the controller using V.42bis. The modem hardware consists of a telephone-line interface and digital-to-analog and analog-to-digital conversion circuitry. The hardware does not contain a DSP or a microcontroller. Compare with controllerless modem.

Sound Blaster

Hardware produced by Creative Labs, Inc., that represents for MS-DOS–based games one of the major hardware interfaces for both audio and music (specifically MIDI) data.

source

In terms of device stacking in kernel streaming or ActiveMovie, indicates that a pin represents possible connections that attach, rather than those that are attached to. Compare with sink.

S/PDIF

Sony/Phillips Digital Interface. The current standard for digital connection to consumer audio devices is the S/PDIF connector. Microsoft is encouraging the use of USB or IEEE 1394 as the digital connection between stereo equipment and PCs rather than adapting S/PDIF to meet PC needs.

SPI

Service Provider Interface. Component in Microsoft networking, TAPI, and other communications technologies.

spin down

A power-management capability in which a hard drive shuts down its spindle motor.

static resources

Device resources, such as IRQ signals, DMA channels, I/O port addresses, and memory addresses, that cannot be configured or relocated.

static VxD

A VxD that is loaded statically during system startup. A static VxD can be loaded in a number of different ways, including device enumeration by the Plug and Play static device enumerator.

STI

Still Image class in the WDM architecture. The class of filters that deal with still-image capture. A WDM STI minidriver provides support for still-image devices under the WDM still-image architecture.

STI plug-in

In the STI class architecture, a module that manages the translation of standard DDI calls to device-specific sequences in order to support vendor-specific device features.

stream

An object representing an entity on an adapter capable of receiving, processing, or supplying data. Notice that a stream is identical to a WDM Stream architecture pin. A stream can accept data from or supply data to the processor, such as a stream representing an MPEG input, or can simply route data through hardware, such as a stream representing an NTSC output jack on the back of an adapter. The purpose of representing nondata hardware with a stream is that the properties of the hardware can be controlled by software.

stream request block

(SRB) The fundamental streaming mechanism to control and make requests of minidrivers. A set of SRBs are provided for each minidriver to access particular capabilities of a given driver and are specific for each data stream supported by the device. An SRB comprises a command and data associated with that command. A HW_STREAM_REQUEST_BLOCK structure contains all information relating to a specific SRB.

SVD

Simultaneous voice/data. A technology used in TAPI-based modem technology.

SVGA

Super VGA. A video standard established by VESA to provide high-resolution color display on IBM-compatible computers. The most commonly implemented SVGA standard is 1024x768 pixels resolution.

S-Video

Also Y/C video. A video signal that separates the luminance and color (Y and C) components of the signal for improved quality over composite video. The type of video signal used in the Hi8 and S-VHS videotape formats. It transmits luminance and color portions separately, using multiple wires, thus avoiding the NTSC encoding process and its inevitable loss of picture quality.

symmetrical compression

A compression system that requires equal processing capability for compression and decompression of an image. This form of compression is used in applications in which both compression and decompression are used frequently. Examples include still-image databasing, still-image transmission (color fax), video production, video mail, videophones, and video conferencing. Compare with asymmetrical compression.

synchronous

Any operation that proceeds under control of a clock or timing mechanism. Compare with asynchronous.

system board

Also motherboard or planar. The primary circuit board in a PC that contains most of the basic components of the system.

system context

The volatile data in the system that is not saved by a device driver.

system devices

Devices on the system board, such as interrupt controllers, keyboard controller, real-time clock, DMA page registers, DMA controllers, memory controllers, FDC, IDE ports, serial and parallel ports, PCI bridges, and so on. In today's PCs, these devices are typically integrated in the supporting chip set.