DDK Glossary - S

SCB

See subsystem control block architecture.

scheduler

A computer program designed to perform functions such as scheduling, initiation, and termination of jobs.

screen

In SAA Basic Common User Access architecture, the physical surface of a display device upon which information is shown to a user.

screen device context

A logical description of a data destination that is a particular window on the screen. See also device context.

SCREEN$

Character-device name reserved for the display screen.

scroll bar

In SAA Advanced Common User Access architecture, a part of a window, associated with a scrollable area, that a user interacts with to see information that is not currently visible.

scrollable entry field

An entry field larger than the visible field.

scrollable selection field

A selection field that contains more choices than are visible.

scrolling

Moving a display image vertically or horizontally in a manner such that new data appears at one edge, as existing data disappears at the opposite edge.

seamless windows

An architecture contained within OS/2 which permits one or more applications to share windowed desktop graphical space and other resources, while executing concurrently. Application session windows managed by seamless windows can share border information, and pointing device transitions from session to session are handled smoothly and transparently.

second-party DMA adapter

See DMA slave.

secondary window

A window that contains information that is dependent on information in a primary window and is used to supplement the interaction in the primary window.

sector

On disk or diskette storage, an addressable subdivision of a track used to record one block of a program or data.

segment

See graphics segment.

segment attributes

Attributes that apply to the segment as an entity, as opposed to the individual primitives within the segment. For example, the visibility or detectability of a segment.

segment chain

All segments in a graphics presentation space that are defined with the 'chained' attribute. Synonym for picture chain.

segment priority

The order in which segments are drawn.

segment store

An area in a normal graphics presentation space where retained graphics segments are stored.

select

To mark or choose an item. Note that select means to mark or type in a choice on the screen; enter means to send all selected choices to the computer for processing.

select button

The button on a pointing device, such as a mouse, that is pressed to select a menu choice. Also known as button 1.

selection cursor

In SAA Advanced Common User Access architecture, a visual indication that a user has selected a choice. It is represented by outlining the choice with a dotted box. See also text cursor.

selection field

(1) In SAA Advanced Common User Access architecture, a set of related choices. See also entry field.

(2) In SAA Basic Common User Access architecture, an area of a panel that cannot be scrolled and contains a fixed number of choices.

semantics

The relationships between symbols and their meanings.

semaphore

(1) An object used by applications for signalling purposes and for controlling access to serially reusable resources.

(2) A variable that is used to enforce mutual exclusion. (T)

(3) An indicator used to control access to a file; for example, in a multiuser application, a flag that prevents simultaneous access to a file.

(4) An entity used to control access to system resources. Processes can be locked to a resource with semaphores if the processes follow certain programming conventions.

sense data

Data which describes an I/O error as defined by the ANSI SCSI specifications.

separator

In SAA Advanced Common User Access architecture, a line or color boundary that provides a visual distinction between two adjacent areas.

serial dialog box

See modal dialog box.

serialization

The consecutive ordering of items.

serialize

To ensure that one or more events occur in a specified sequence.

serially reusable resource (SRR)

A logical resource or object that can be accessed by only one task at a time.

session

(1) A routing mechanism for user interaction via the console; a complete environment that determines how an application runs and how users interact with the application. OS/2 can manage more than one session at a time, and more than one process can run in a session. Each session has its own set of environment variables that determine where OS/2 looks for dynamic-link libraries and other important files.

(2) In the OS/2 operating system, one instance of a started program or command prompt. Each session is separate from all other sessions that might be running on the computer. The operating system is responsible for coordinating the resources that each session uses, such as computer memory, allocation of processor time, and windows on the screen.

Settings Notebook

A control window that is used to display the settings for an object and to enable the user to change them.

shadow

An object that refers to another object. A shadow is not a copy of another object, but is another representation of the object.

shadow box

The area on the screen that follows mouse movements and shows what shape the window will take if the mouse button is released.

shared data

Data that is used by two or more programs.

shared memory

In the OS/2 operating system, a segment that can be used by more than one program.

shear

In computer graphics, the forward or backward slant of a graphics symbol or string of such symbols relative to a line perpendicular to the baseline of the symbol.

shell

(1) A software interface between a user and the operating system of a computer. Shell programs interpret commands and user interactions on devices such as keyboards, pointing devices, and touch-sensitive screens, and communicate them to the operating system.

(2) Software that allows a kernel program to run under different operating-system environments.

shutdown

The process of ending operation of a system or a subsystem, following a defined procedure.

sibling processes

Child processes that have the same parent process.

sibling windows

Child windows that have the same parent window.

simple list

A list of like values; for example, a list of user names. Contrast with mixed list.

single-byte character set (SBCS)

A character set in which each character is represented by a one-byte code. Abbreviated as SBCS. Contrast with double-byte character set.

slider box

In SAA Advanced Common User Access architecture: a part of the scroll bar that shows the position and size of the visible information in a window relative to the total amount of information available. Also known as thumb mark.

Small Computer System Interface (SCSI)

An input and output bus that provides a standard interface between the OS/2 multimedia system and peripheral devices. Abbreviated as SCSI.

spline

(1) A sequence of one or more Bézier curves.

(2) In computer graphics, a shape created when a user specifies a series of points and the computer software draws a curve that smoothly approaches those points.

spooler

A program that intercepts data going to a device driver and writes it to a disk. The data is later printed or plotted when the required device is available. A spooler prevents output from different sources from being intermixed.

stack

A list constructed and maintained so that the next data element to be retrieved is the most recently stored. This method is characterized as last-in-first-out (LIFO).

standard window

A collection of window elements that form a panel. The standard window can include one or more of the following window elements: sizing borders, system menu icon, title bar, maximize/minimize/restore icons, action bar and pull-downs, scroll bars, and client area.

static control

The means by which the application presents descriptive information (for example, headings and descriptors) to the user. The user cannot change this information.

static storage

(1) A read/write storage unit in which data is retained in the absence of control signals. Static storage may use dynamic addressing or sensing circuits. (A)

(2) Storage other than dynamic storage. (A)

style

See window style.

subclass

A class that inherits from another class. See also inheritance.

subdirectory

In an IBM personal computer, a file referred to in a root directory that contains the names of other files stored on the diskette or fixed disk.

superclass

A class from which another class inherits. See also inheritance.

swapping

(1) A process that interchanges the contents of an area of real storage with the contents of an area in auxiliary storage. (I) (A)

(2) In a system with virtual storage, a paging technique that writes the active pages of a job to auxiliary storage and reads pages of another job from auxiliary storage into real storage.

(3) The process of temporarily removing an active job from main storage, saving it on disk, and processing another job in the area of main storage formerly occupied by the first job.

switch

(1) In SAA usage, to move the cursor from one point of interest to another; for example, to move from one screen or window to another or from a place within a displayed image to another place on the same displayed image.

(2) In a computer program, a conditional instruction and an indicator to be interrogated by that instruction.

(3) A device or programming technique for making a selection, for example, a toggle, a conditional jump.

switch list

See Task List.

symbolic identifier

A text string that equates to an integer value in an include file, which is used to identify a programming object.

symbols

In Information Presentation Facility, a document element used to produce characters that cannot be entered from the keyboard.

synchronous

Pertaining to two or more processes that depend upon the occurrence of specific events such as common timing signals. (T) See also asynchronous.

System Menu

In the Presentation Manager, the pull-down in the top left corner of a window that allows it to be moved and sized with the keyboard.

System Object Model (SOM)

A mechanism for language-neutral, object-oriented programming in the OS/2 environment. Abbreviated as SOM.

system queue

The master queue for all pointer device or keyboard events.

system-defined messages

Messages that control the operations of applications and provide input and other information for applications to process.

Systems Application Architecture (SAA)

A set of IBM software interfaces, conventions, and protocols that provide a framework for designing and developing applications that are consistent across systems. Abbreviated as SAA.