Glossary

S

S-connector. The type of connector used with super-video. Similar to the Y/C connector. It is a 4-pin-min din-type connector.

S-video. Super-video. Used to improve the quality of a video image, a technique that maintains separate Y/C signals before recording on magnetic tape or displaying on a monitor.

SABM. See set asynchronous balanced mode.

SAK. See secure attention key.

sample rate. Synonym for locator sample rate.

SAP. See service access point.

SAS. Single-attachment station. A station that connects only to the primary ring by way of a wiring concentrator or connects to one other SAS in a back-to-back wiring configuration.

sash. In CDE, a box on a separator or split bar that enables you to increase or decrease the size of a window pane using the mouse. You can navigate to the sash using the keyboard.

satisfy. For Ada programming, see constraint and subtype.

saved user ID. The user ID that is acquired when running a setuid program. The saved user ID is the same as the owner of the file that ran. If the file that ran was not setuid, the saved user ID is set to the effective user ID of the parent.

saveset. A list of window clients that should not be destroyed when a connection is closed and should be remapped or unmapped. Usually used by window managers to avoid lost windows if the manager is ended abnormally.

scalability. The ability of a workload to benefit from a multiprocessor environment.

scalar. An arithmetic object or enumerated object.

scalar type. A type that defines a variable containing a single value at run time. Contrast with structured type. In Ada programming, an object or value of a scalar type does not have components. A scalar type is either a discrete type or a real type. The values of a scalar type are ordered.

scale. Increments of measure used by the nroff and troff commands. All supported scales are converted for the typesetter into a scale called machine units (u).

scale factor. (1.) A number indicating the position of the decimal point in a real number. (2.) A number used as a multiplier in scaling.

scaling. (1.) In computer graphics, enlarging or reducing all or part of a display image by multiplying the coordinates of the image by a constant value. (2.) In programming, indicating the number of digit positions in object code to be occupied by the fractional portion of a fixed-point or floating-point constant. (3.) In GL, uniform stretching of a primitive along an axis.

scaling factor. The throughput of a workload on a multiprocessor divided by the throughput of that workload on a comparable uniprocessor (not on a single-processor SMP system).

scan. (1.) To examine sequentially, part by part. (2.) To search records for a specified character string or syntax error.

scan code. Raw input from the keyboard.

scan conversion. The process of generating pixel information into the frame buffer from an application program.

scanline. (1.) A list of pixel or bit values viewed as a horizontal row (all values have the same y coordinate). The values are ordered by increasing the x coordinate. As part of an image, the next scanline is ordered by increasing the y coordinate. (2.) A visible line produced on a display by one horizontal sweep of the electron beam of a cathode ray tube.

scanline order. An image represented by scanlines ordered by increasing the y coordinate.

scanned image. An image that is examined sequentially, part by part.

scatter. For input and output operations, to read data from a device and locate it in noncontiguous memory addresses. Contrast with gather.

SCCS. See Source Code Control System and Revision Control System.

SCCS delta. A set of changes made to an SCCS file. Creating a new delta saves only the changes made.

SCCS identification (SID). In SCCS, a number assigned to each version of a program.

scheduling policy. The set of rules that govern when a thread will lose control of the CPU and which thread will get control next.

scope. (1.) That part of a source program in which a variable can communicate its value. (2.) The portion of a program within which a declaration applies. For Ada programming, see declaration. (3.) In SOM, that portion of a program within which an identifier name has "visibility" and denotes a unique variable. In SOM, an IDL source file forms a scope. An identifier can only be defined once within a scope; identifiers can be redefined within a nested scope. In a .idl file, modules, interface statements, structures, unions, methods, and exceptions form nested scopes.

scope of resource collection. In Workload Management, the scope of resource collection specified for a class determines how resource limits are applied to the processes in that class. The scope levels can be set to class, process, user, or group.

scope operator (::). Defines the scope for the right argument in C++. If the left argument is blank, the scope is global. If the left argument is a class name, then the scope is within that class.

scratch file. A file, usually used as a work file, that exists temporarily, until the end of the program that uses it.

screen. (1.) See display screen. (2.) In the extended curses library, a special type of window that is as large as the workstation screen. (3.) In Enhanced X-Windows, a server can provide several independent screens that typically have physically independent monitors (display screens). This is the expected configuration when there is only a single keyboard and pointer shared among the screens. A screen structure contains the information about that screen and is linked to the display structure.

screen capture. The storage of a screen display as a text or graphics file on disk.

screen coordinates. The coordinate system that defines the display screen. In GL, distances are measured in units of pixels, and the origin is in the lower left-hand corner. On most systems the screen size is 1024 pixels high by 1280 pixels wide. The viewport defines the mapping from normalized device coordinates to screen coordinates. Synonymous with screen space. See also eye coordinates, primitive coordinates, modeling coordinates, world coordinates, and transformation.

screen lock. In CDE, a function that locks the workstation screen, barring further input until the valid user password is entered.

Screen Saver. In CDE, a choice that, after a specified time period, switches off the workstation display or varies the images that are displayed, thereby prolonging the life of the screen.

screen space. Synonym for screen coordinates.

screenmask. In GL, a rectangular area of the screen to which all drawing operations are clipped. It is normally set equal to the viewport and to the window. A screenmask is useful for character clipping. See also clipping.

script file. In the Ada debugger, a file that contains a series of commands that can be used to drive the debugger. Script files are useful for debugging large, complex programs when you may not be able to complete a debugging session in one sitting.

scroll. To move text vertically or horizontally in order to view information that is outside the display or pane boundaries.

scroll bar. The horizontal and vertical bars in the border of a directory window that allow you to scroll the files to see what is beyond the border of the window. A graphical device consisting of a slider, scroll area, and scroll arrows. A user changes the view by sliding the slider up or down in the scroll area or by pressing one of the scroll arrows. This causes the view to scroll up or down in the window adjacent to the scroll bar.

scroll region. In AIXwindows, the rectangular portion of a ScrollBar widget that contains two arrows and a slider.

scrolled list. A list that is scrolled. See also scroll.

scrolled text. Text that is scrolled. See also scroll.

scrolling. The horizontal or vertical movement of graphic or text information presented on a display screen.

SCSI Adapter. See Small Computer Systems Interface Adapter.

sdb. See symbolic debugger.

SDLC. See synchronous data link control.

SDLC primary station. A station that has responsibility for the data link. It issues commands to secondary stations.

SDLC secondary station. A station that responds to requests from another station (the primary station) and has little control over data link operations.

SDT. See static debugger trap.

seal. To encrypt a record containing several fields in such a way that the fields cannot be modified without either knowledge of the encryption key or leaving evidence of tampering.

search. The action of scanning a set of data elements to locate all instances of a particular item, such as a text string or a file name.

search loop. An array-processing loop used to perform a table lookup or to find exceptional values within an array.

SECAM. A national television industry broadcasting standard used in France, USSR, and some other countries. See also NTSC and PAL.

second-level interrupt handler (SLIH). A device-dependent routine that handles the processing of an interrupt from a specific adapter. An SLIH is called by the first-level interrupt handler (FLIH) associated with that interrupt level.

secondary key. A key field of a record that defines a secondary index.

secondary representation. A second form, an alternative to the primary representation, in which the client may supply an attribute value to the service.

secondary station. A data station that runs data link control functions as instructed by the primary station. It interprets received commands and generates responses for transmission.

secondary unit. In Ada language, the body of a library unit (such as a subprogram body, package body, generic body, or subprogram body) or a subunit. All compilation units that are not library units are secondary units. Secondary units are not subject to reference by other independently compiled units and can be thought of as the hidden implementation of a library unit or separate declaration.

secondary window. A window of short duration such as a dialog box. The window is only displayed for a short time, usually just long enough to convey some information or get some operational directions.

section. In the vi editor, text that follows a section heading as defined by the sect= option.

sector. (1.) The smallest amount of information that can be written to or read from a disk or diskette during a single read or write operation. (2.) On disk or diskette storage, an addressable subdivision of a track used to record one block of a program or data.

secure attention key (SAK). A key sequence that ends all processes associated with a terminal to provide a trusted path for secure communication with the TCB. The SAK sequence is Ctrl-x followed by Ctrl-r.

secure node. A node that is capable of running one or more application servers and one or more Monitor system components, normally a highly trusted machine.

security. The protection of data, system operations, and devices from accidental or intentional ruin, damage, or exposure.

seek pointer. A data structure that contains the offset of the current location in a character file or device.

segment. (1.) A contiguous area of virtual storage allocated to a job or system task. A program segment can be run by itself, even if the whole program is not in main storage. (2.) Virtual memory is divided into segments that are linearly-addressable spaces of one or more 4KB-byte pages up to a maximum size of 2 to the 28th power bytes. (3.) The information that can be addressed via a single, unique segment-register value (256MB). (4.) A portion of a computer program that can be run as an entity without the entire program being maintained in system memory. (5.) A group of display elements. (6.) In Enhanced X-Windows, one or more lines that are drawn but not necessarily connected at the end points.

segment flag. The segflag parameter of the fp_open kernel service that indicates whether the path parameter is located in user space or in kernel space.

segment registers. Registers in the system that hold the actual addresses of the memory segments currently in use.

segment unit. In Pascal, an independently compilable piece of code containing routines linked with the program unit. See also program unit.

segmentation fault. A memory addressing exception. Occurs when a memory location is referenced that has not been allocated to the referencing process. An out-of-bounds array reference or incorrect use of a pointer can cause a segmentation fault.

segmenting of BIUs. An optional function of path control that divides a basic information unit (BIU) received from transmission control into two or more path information units (PIUs). The first PIU contains the request header of the BIU and usually part of the response unit (RU). The remaining PIU or PIUs contain the remaining parts of the RU.

select. (1.) To choose a button on the display screen. (2.) To place the cursor on an object (name or command) and press the Select (left) button on the mouse or the Select key on the keyboard. (3.) To indicate the item or items the next command you choose will affect. The item may be highlighted to confirm your selection. Selecting does not actually carry out the command.

selected component. In Ada language, a name consisting of a prefix and of an identifier called the selector. Selected components are used to denote record components, entries, and objects designated by access values; they are also used as expanded names.

selecting. In GL, a method for finding what primitives are being drawn in a given volume in three-dimensional space. See also hit, selecting region, picking, and picking region.

selecting region. In GL, a rhomboid-shaped volume in world coordinates that is sensitive to selecting events. If a drawing primitive draws within this region, a select event is reported. See also hit, selecting, picking, transformation, and picking region.

selection. (1.) Addressing a workstation or a component on a selective calling circuit. (2.) The process by which a computer requests a station to send it a message. (3.) See also addressing. (4.) In Enhanced X-Windows, an indirect property of a dynamic type maintained by the client (the owner) but belonging to the user. It is not private to a particular window subhierarchy or a particular set of clients. When a client asks for the contents of a selection, it specifies a target type. This target type can be used to control the transmitted representation of the contents.

selection area. In AIXwindows, a portion of a RowColumn widget over which the mouse pointer can be placed to select other widgets.

selection criteria. In the select subroutine, the readlist, writelist, and exceptlist parameter values that specify what to check for reading, writing, and exceptions.

selection range. See key range.

selector. (1.) In Pascal, the term in a CASE statement that, once evaluated, determines which of the possible branches of the CASE statement are processed. (2.) For Ada programming, see selected component.

semantic. The relationships of characters or groups of characters to their meanings, independent of the manner of their interpretation and use.

semantic error. A compile-time error caused by incorrect definition of constants and identifiers. See also syntax error.

semaphore. (1.) Entity used to control access to system resources. Processes can be locked to a resource with semaphores if the processes follow certain programming conventions. (2.) Provides a general method of communication between two processes that is an extension of the features of signals.

semaphore ID (semid). An integer that points to a set of semaphores and a data structure that contains information about the semaphores.

semid. See semaphore ID.

send pacing. In SNA, the pacing of message units that a component is sending. Contrast with receive pacing.

sense code. A value sent or received, or a negative response to indicate what error occurred.

sentence. In the vi editor, text that is separated from other text by a . (period), ! (exclamation point), or ? (question mark) followed by two spaces.

separator. A punctuation character that separates parts of a command or file, or that delimits character strings.

sequential access. (1.) An access method in which records are read from, written to, or removed from a file based on the logical order of the records in the file. (2.) The facility to obtain data from or enter data into a storage device so that the process depends on the location of the data and on a reference to data previously accessed.

sequential file access. The location of a range of records through key values and the subsequent processing of them in some order related to those key values. The index of the file need not be unique.

sequential I/O model. A model of the operating system for all accesses to system network resources. When SNA supports this model, it simplifies access to the network, allows programs to be designed for portability, and allows programs to use network resources through redirection.

serial device. A device that performs functions sequentially, such as a serial printer that prints one character at a time. Contrast with parallel device.

serial port. A port used for a serial device. See also serial device.

serial processing. Pertaining to the sequential or consecutive running of two or more processes in a single device, such as a channel or processing unit. Contrast with parallel processing.

serial transmission. Transmitting each bit of a data character separately over the same electrical path.

serializability. A basic property of transaction processing systems, this refers to the idea that the exchange and modification of information by transactions must be able to be synchronized and appear as though multiple, simultaneous transactions are actually a series of sequential requests. Data being changed by a transaction, or upon which a transaction depends, must be shielded from other transactions until the first transaction completes.

serialize. (1.) To change from parallel-by-byte to serial-by-bit. (2.) In XDR, to convert a particular machine representation to XDR format.

server. (1.) An application program that usually runs in the background (daemon) and is controlled by the System Program Controller. (2.) On a network, the computer that contains the data or provides the facilities to be accessed by other computers on the network. (3.) A program that handles protocol, queuing, routing, and other tasks necessary for data transfer between devices in a computer system. (4.) In Enhanced X-Windows, provides the basic windowing mechanism. It handles IPC connections from clients, de-multiplexes graphics requests onto screens, and multiplexes input back to clients. (5.) In NCS, a process that exports one or more interfaces to one or more objects, and whose procedures can be invoked from remote hosts. (6.) In DSOM, a process, running in a distributed environment, that executes the implementation of an object. DSOM provides a default server implementation that can dynamically load SOM class libraries, create SOM objects, and make those objects accessible to clients. Developers can also write application-specific servers for use with DSOM.

server grabbing. When a client seizes the server for exclusive use to prevent processing requests from other client connections until the grab is complete. This is typically a transient state for such things as rubber-banding and pop-up menus or to run requests indivisibly.

server object. In DSOM, every serverhas an object that defines methods for managing objects in that server. These methods include object creation, object destruction, and maintaining mappings between object references and the objects they reference. A server object must be an instance of the class SOMDServer (or one of its subclasses). See also object reference and SOMDObject.

server reporting. A protocol for servers to report to the cell manager contact by previously unknown clients, for the purpose of registration.

service access point (SAP). In the Ethernet logical link profile, the address for the transaction program on the local system. This address is a hexadecimal value.

service controls. A group of parameters, applied to all directory operations, that direct or constrain the provision of the service.

service mode. Synonym for maintenance mode.

service request number (SRN). A group of numbers used by service technicians to determine the failing area of the system.

service transaction program. (1.) A program that provides a function internal to SNA Server. (2.) A transaction program implemented by a transaction processing system. Service transaction programs perform such functions as providing access to remote data bases and remote queues. See also application transaction program and transaction program.

service update. Software that corrects a defect in or adds new function to the Base Operating System (BOS) or to an optional software product. See also maintenance level update.

session. (1.) The period of time during which programs or devices can communicate with each other. (2.) A name for a type of resource that controls local LUs, remote LUs, modes, and attachments. (3.) In network architecture, an association of facilities that establish, maintain, and release connections for communication between stations. (4.) The period of time during which the user of a workstation can communicate with an interactive system, usually elapsed time between login and logoff. (5.) In SNA, a logical connection between two network addressable units (NAUs) that can be activated, tailored to provide various protocols, and deactivated as requested. (6.) In remote communications, a period of communication with a remote system or host system.

session date. The date associated with a session. See also creation date and system date.

session key. Used in Kerberos specifications. See also conversation key.

session-level pacing. In SNA, a flow control technique in which a receiving half-session controls the data transfer rate (the rate at which it receives request units). It is used to prevent overloading a receiver with unprocessed requests, when the sender can generate requests faster than the receiver can process them.

Session Manager. In CDE, a software application that controls saving sessions, restoring sessions, screen locking and unlocking, and the use of screen savers. When a session is saved, the state of the desktop environment (location of icons, size and location of open windows, open/closed status of applications, current color palette, and so on) is preserved so that it can be restored at the next login.

session profile. For the 3270 Host Connection Program 2.1 and 1.3.3, a profile describing the characteristics of a session between a client system and a System/370 host computer. See also 3270 Host Connection Program and profile.

session records. In the accounting system, a record (produced from log in and log off records) of time connected and line usage for connected display stations.

session server. In CDE, a system that provides networked sessions. Session files reside on the session server and are used whenever you log in to a system on the network.

set. In NCS, to associate an allocated Remote Procedure Call (RPC) handle with a specific socket address. See also bind.

set-associative cache. A cache in which two or four (or more) lines correspond to each possible value of the virtual-address field that identifies the line to be interrogated during cache lookup.

set associativity. An aspect of cache design that determines how many cache lines can be associated with a given memory location. A cache that is four-way set associative can contain a given memory location in one of four cache lines. See also cache line.

set asynchronous balance mode (SABM). A link control frame.

set flags. Flags that can be put into effect with the shell set command.

set-group-ID mode bit. In setting file access permissions, sets the effective and saved group IDs of the process to the group ID of the file on execution.

set-user-ID mode bit. In setting file access permissions, sets the effective and saved user IDs of the process to the owner ID of the file on execution.

setgid. See set-group-ID mode bit.

setuid. See set-user-ID mode bit.

severity code. A code that indicates how serious an error condition is.

shadow. A darkened area below a window and to its right, or above it and to its left, which represents the shadow a window might cast.

shadow color. The shaded area around or behind a dialog box.

shadow widget. An opaque pointer to a structure created each time a widget is created; it identifies the widgets in the interface. Also called swidget.

shadowing. In the SOM Emitter Framework, a technique that is required when any of the entry classes are subclassed. Shadowing causes instances of the new subclass(es) (rather than instances of the original entry classes) to be used as input for building the object graph, without requiring a recompile of emitter framework code. Shadowing is accomplished by using the macro SOM_SubstituteClass.

shared library. A library created by the ld command that contains at least one subroutine that can be used by multiple processes. Programs and subroutines are linked as before, but the code common to different subroutines is combined in one library file that can be loaded at run time and shared by many programs. A key to identify the shared library file is left in the header of each subroutine.

shared locks. Shared locks are a type of lock in which multiple transactions can simultaneously lock a data item for reading. See also exclusive lock.

shared memory. An area of memory simultaneously accessible to more than one cooperating process.

shared memory ID (shmid). An identifier assigned to the shared segment for use within a particular process. See also file descriptor.

shared port. A port used by communications applications (for example, UUCP) to ensure exclusive access to a port.

Shared Product Object Tree (SPOT). (1.) A version of the /usr file system that diskless clients mount as their own /usr directory. (2.) For NIM, a /usr file system or an equivalent file system that is exported by servers in the NIM environment for remote client use.

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. (3.) The command interpreter that provides a user interface to the kernel. See also shell program and command interpreter. Synonymous with interface. (4.) A shell is a command interpreter that acts as an interface between users and the operating system. A shell can contain another shell nested inside it, in which case, the outer shell is the parent shell and the inner shell is the child. (5.) In AIXwindows, Shell widgets are top-level widgets that are internal and cannot be instantiated, but they provide the necessary interface with the window manager. See also shell widget.

shell box. A geometry management technique where a type of bounding box can have only one child that is exactly the same size as the shell.

shell command names. Operating-system commands.

shell control command. A command that enables the user to pass control to various parts of a shell procedure, or to control how a procedure ends.

shell procedure. A series of commands, combined in a file, that carry out a particular function when the file is run or when the file is specified as a value to the sh command. Synonymous with shell script.

shell program. A program that accepts and interprets commands for the operating system. Synonym for shell.

shell prompt. The character string on the command line indicating that the system can accept a command (typically the $ character).

shell script. Synonym for shell procedure.

shell variables. Facilities of the shell program for assigning variable values to constant names.

shell widget. In Enhanced X-Windows, holds the top-level widgets that communicate directly with the window manager. These widgets do not have parents. Synonymous with shell. See also widget.

shielded twisted pair. A transmission medium of two twisted conductors with a foil or braid shield.

Shift-Japanese Industrial Standard (SJIS). An encoding scheme consisting of single bytes and double bytes used for character encoding. Because of the large number of characters in Japanese and other Asian languages, the 8-bit byte is not sufficient for character encoding.

shmid. See shared memory ID.

short. In ODM, a terminal descriptor type used to define a variable as a signed 2-byte number. See also terminal descriptor.

short circuiting. The evaluation of Boolean expressions with AND and OR such that the right operand is not evaluated if the result of the operation can be determined by evaluating the left operand. The evaluation of the expression is always from left to right.

short status. Status output in abbreviated form (short form) from the spooling subsystem.

shortest-job-next (SJN). A method of queueing jobs where the shortest jobs are printed first. Contrast with first-come-first-served. See also discipline.

sibling. Children of the same parent window.

SiCounter. In Performance Toolbox, a value that is incremented continuously. Instruments show the delta (change) in the value between observations, divided by the elapsed time, representing a rate per second.

SID. SCCS identification. The name assigned to a delta.

side effect. An undesirable result caused by altering the values of nonlocal variables by a procedure or function.

sign-off. To end a session at a display station.

sign-on. To begin a session at a display station.

signal. (1.) A simple method of communication between two processes. One process can inform the other process when an event occurs. (2.) In operating system operations, a method of inter-process communication that simulates software interrupts. Contrast with exception and interrupt.

signal handler. A subroutine called when a signal occurs.

signal mask. Defines the set of signals currently blocked from delivery to a process.

signal stack. An alternate stack on which signals are to be processed.

signature. In SOM, the collection of types associated with a method (the type of its return value, if any, as well as the number, order, and type of each of its arguments).

signed. Information is digitally signed by appending to it an enciphered summary of the information. This is used to ensure the integrity of the data, the authenticity of the originator, and the unambiguous relationship between the originator and the data.

Simple Mail Transfer Protocol (SMTP). A protocol, typically used over a network, in which the objective is to transfer mail. SMTP is used by the sendmail command to accept and receive mail.

simple name. For Ada programming, see declaration and name.

simultaneous peripheral operation online. See spooling.

single buffer mode. . In GL, a mode in which the frame buffer bitplanes are organized into a single large frame buffer. This frame buffer is the one currently displayed and is also the one in which all drawing occurs. See also double buffer mode.

single-byte control codes. ASCII codes 0 through 31 (0x00 through 0x1f) and delete (0x7f).

single-mode optical fiber. An optical fiber in which only the lowest-order bound mode (which can consist of a pair of orthogonally polarized fields) can propagate at the wavelength of interest. Contrast with multimode optical fiber.

single-precision. (1.) The use of one computer word to represent a number, in accordance with the required precision. (2.) The specification that causes a floating-point value to be stored in the short format. See also precision.

single-processor SMP. A system designed to handle two or more processors, running the SMP version of the operating system, which has been configured with a single processor. Contrast with uniprocessor.

single-shift control. In codepage switching, control codes that shift to another page for a single character; nonlocking shifts.

SiQuantity value. In Performance Toolbox, represents a level, such as memory used or available disk space. The actual observation value is shown by instruments.

sister class object. In SOM, a duplicate of a class object that is created in order to save a copy of the class's original method table before replacing the method table to customize method resolution. The sister class object is created so that some original method procedures can be called by the replacement method procedures.

size. The screen management action that changes the size of a window.

size field. In an i-node, a field that indicates the size, in bytes, of the file associated with the i-node.

SJIS. See Shift-Japanese Industrial Standard.

SJN. See shortest-job-next.

skew. The time difference between two clocks or clock values.

SLA. Serial Link Adapter. See also SOCC.

sleeping process. A process that is waiting for input or output to complete, time slices, an event to occur, or signals from other processes. When a process is sleeping, it can be paged out of memory.

slider. (1.) In AIXwindows, a small interactive graphical object connected to an XmScrollBar bar widget. The slider controls the vertical or horizontal movement of text information or graphics across the display screen. (2.) A control that uses a track and arm to set a value from among the available values. The position of the arm (or a separate indicator) gives the currently set value.

SLIH. See second-level interrupt handler.

SLIP. Serial Line Interface Protocol. The protocol that TCP/IP uses when operating through a serial connection.

slot. A long electrical socket inside the system unit into which an electronic circuit board (card) is installed.

slow list. A list of secondary stations on a multidrop network that, due to their inactivity, are polled less often by the primary station.

small caps. See caps.

Small Computer Systems Interface Adapter (SCSI Adapter). An adapter that supports the attachment of various direct-access storage devices and tape drives to the system unit.

small word. In the vi editor, a contiguous set of alphanumeric characters bounded on at least one end with a character that is not a blank, a tab, or a new-line indicator. For example, in the word isn't, the two sets of characters isn and t are small words. Contrast with big word.

SMIT. System Management Interface Tool.

SMP. See symmetrical multiprocessor system.

SMP efficient. Avoidance in a program of any action that would cause functional or performance problems in an SMP environment. A program that is described as SMP efficient is generally assumed to be SMP safe as well. An SMP-efficient program has usually undergone additional changes to minimize incipient bottlenecks.

SMP exploiting. Adding features to a program that are specifically intended to make effective use of an SMP environment. A program that is described as SMP exploiting is generally assumed to be SMP safe and SMP efficient as well.

SMP safe. Avoidance in a program of any action, such as unserialized access to shared data, that would cause functional problems in an SMP environment. This term, when used alone, usually refers to a program that has undergone only the minimum changes necessary for correct functioning in an SMP environment.

SMT. Station management.

SMTP. See Simple Mail Transfer Protocol.

SNA. See System Network Architecture.

SNA network. The part of a user-application network that conforms to the formats and protocols of System Network Architecture (SNA). It enables reliable transfer of data among end users and provides protocols for controlling the resources of various network configurations. The SNA network consists of network addressable units (NAUs), boundary-function components, and the path control network.

SNBU. See switched network backup.

SNMP. Simple Network Management Protocol. A protocol used by network hosts to exchange information in the management of networks. SNMP network management is based on the client-server model that is widely used in TCP/IP-based network applications.

SNOBOL. A programming language designed for string processing and pattern matching.

SOCC. Serial Optical Channel Converter. A 220-Mbit/sec optical point-to-point link.

social science format. See natural or social science format.

socket. (1.) A unique host identifier created by the concatenation of a port identifier with a TCP/IP address. (2.) A port identifier. (3.) A 16-bit port number. (4.) In NCS, a port on a specific host; a communications end point that is accessible through a protocol family's addressing mechanism. A socket is identified by a socket address. See also socket address, port, and listening.

socket address. A data structure that uniquely identifies a specific communications end point. A socket address consists of a port number and a network address. It also specifies the protocol family. See also protocol family.

Sockets class. A SOM class that provides a common communications interface to Distributed SOM, the Replication Framework, and the Event Management Framework. The Sockets class provides the base interfaces (patterned after TCP/IP sockets); the subclassesTCPIPSockets, NBSockets, and IPXSockets provide actual implementations for TCP/IP , Netbios, and Netware IPX/SPX, respectively.

software. Programs, procedures, rules, and any associated documentation pertaining to the operation of a system. Contrast with hardware.

software configuration. The processing required to make installed software ready to use.

software installation. The process of restoring software from external media to a local file system. The software can require further processing, or configuration, before it is ready to use.

software keyboard. A table mapping a raw keystroke to a display symbol, predefined function or string. Software keyboards that are shipped with the operating system are associated with languages (U.S. English, U.K. English, Danish, Japanese, and so on).

software keyboard map. A table that maps a keystroke to a character or to a predefined function such as a tab.

Software Vital Product Data (SWVPD). Information that uniquely defines system, hardware, software, and microcode elements of a processing system.

SOM. See System Object Model.

SOM Compiler. A tool provided by the SOM Toolkit that takes as input the interface definition file for a class (the .idl file) and produces a set of binding files that make it more convenient to implement and use SOM classes.

SOM-derived metaclass. See derived metaclass.

SOMClass. One of the three primitive class objects of the SOM run-time environment. SOMClass is the root (meta)class from which all subsequent metaclasses are derived. SOMClass defines the essential behavior common to all SOM class objects.

SOMClassMgr. One of the three primitive class objects of the SOM run-time environment. During SOM initialization, a single instance (object) of SOMClassMgr is created, called SOMClassMgrObject. This object maintains a directory of all SOM classes that exist within the current process, and it assists with dynamic loading and unloading of class libraries.

SOMDObject. The SOM class that implements the notion of a CORBA "object reference" in DSOM. An instance of SOMDObject contains information about an object's server implementation and interface, as well as a user-supplied identifier. See also object reference.

somId. In SOM, a pointer to a number that uniquely represents a zero-terminated string. Such pointers are declared as type somId. In SOM, somId's are used to represent method names, class names, and so forth. See also method ID.

SOMOA (SOM object adapter) class. In DSOM, a class that dispatches methods on a server's objects, using the SOM Compiler and run-time support. The SOMOA class implements methods defined in the abstract BOA class (its base class). See also BOA class and ORB (object request broker).

SOMObject. One of the three primitive class objects of the SOM run-time environment. SOMObject is the root class for all SOM (sub)classes. SOMObject defines the essential behaviorcommon to all SOM objects.

somSelf. In SOM, within method procedures in the implementation file for a class, a parameter pointing to the target object that is an instance of the classbeing implemented. It is local to the method procedure.

somThis. In SOM, within method procedures, a local variable that points to a data structure containing the instance variables introduced by the class. If no instance variables are specified in the SOM IDL source file, then the somThis assignment statement is commented out by the SOM Compiler.

sort. To rearrange some or all of a group of items, based upon the contents or characteristics of those items.

source. (1.) A system, a program within a system, or a device that makes a request to a target. Contrast with target. (2.) In advanced program-to-program communications, the system or program that starts jobs on another system.

source code. The input to a compiler or assembler, written in a source language. Contrast with object code.

Source Code Control System (SCCS). A program for maintaining version control for the source files of a developing program. It stores the changes made to a file instead of the changed file, thus allowing several versions of the same file to exist in the system. See also Revision Control System.

source documents. Verbal information produced concurrently with the original software, by the original development company.

source file. A file that contains source statements for such items as high-level language programs and data description specifications. A file containing input data or commands.

source module. See source program.

source program. A computer program expressed in a source language.

source statement. A statement written in a programming language.

space. (1.) A site intended for storage of data, such as a location in a storage medium. (2.) A basic unit of area, usually the size of a single character. (3.) One or more space characters. (4.) In a neutral circuit, an impulse that causes the loop to open or causes absence of signal. In a polar circuit, it causes the loop current to flow in a direction opposite to that for a mark impulse. A space impulse is equal to a binary zero.

sparse array. An array in which few of the defined cells are used.

sparse file. A file that is created with a length greater than the data it contains, leaving empty spaces for future addition of data. See also hole in a file

SPC. See System Program Controller.

special character. A character other than a letter or number. For example, *, +, and % are special characters.

special file. Used in the operating system to provide an interface to input/output devices. There is at least one special file for each device connected to the computer. Contrast with directory and file. See also block file and character special file.

specific. The attribute types that may appear in an instance of a given class, but not in an instance of its superclasses.

specification statement. In FORTRAN, one of the set of statements that provide the compiler with information about the data used in the source program and how to allocate storage.

specifiers. Used in C++ declarations to indicate storage class, fundamental data type, and other properties of the object or function being declared.

speed. The baud rate. Synonym for line speed.

SPI. Stub programming interface. A private RPC runtime interface whose routines are unavailable to application code.

spill area. A storage area used to save the contents of registers.

Spmi. See System Performance Measurement Interface.

spool file. (1.) A disk file containing output that has been saved for later printing. (2.) Files used in the transmission of data among devices.

spooler. A synonym for the queueing system that pertains to its use for queueing print jobs.

spooling (simultaneous peripheral operation online). (1.) The use of auxiliary storage as a buffer storage. This reduces processing delays when transferring data between peripheral equipment and the processors of a computer. (2.) Reading and writing input and output streams on an intermediate device in a format convenient for later processing. (3.) Performing a peripheral operation such as printing while the computer is busy with other work.

SPOT. See Shared Product Object Tree.

SPP. Sequence packet protocol. The primary transport-layer protocol in the Xerox Network Systems. It provides reliable, flow-controlled, two-way transmission of data for an application program. It is a byte-stream protocol used to support the SOCK_STREAM abstraction. The SPP protocol uses the standard Network System (NS) address formats.

spring-loaded pop-up. A kind of widget, such as a menu, that is not visible to the window manager. The spring-loaded pop-up disables user-event processing except for events that occur in the menu.

SRC. System Resource Controller.

SRF. Standard record format.

SRN. See Service request number.

SRT. See Structure Rule Table.

SSCP. See system services control point.

stack. (1.) An area in storage that stores temporary register information and return addresses of subroutines. (2.) A list constructed and maintained so that the last data element stored is the first data element retrieved. (3.) In kernel mode, an area that is paged with the user process. The kernel maintains a stack for each process. It saves the process information such as the call chain and local variables used by the kernel for the user process.

stack buffer. A storage area that stores retrievable data in sequence. The last text stored is the first text removed.

stack overflow. An error condition in DOS that results from an insufficient number of stack frames, which are used by DOS to handle hardware interrupts.

stack pointer. A register providing the current location of the stack.

stack traceback. The calling sequence that indicates the path taken by a process to get to its current location.

stacked tape. A bootable tape with multiple software images.

stacking order. The relationship between sibling windows that stack on top of each other.

stage. One of a series of steps to enter a ged subcommand that typically ends with < cr > (carriage return). Each subcommand consists of a subset of stages, including command line, text, points, pivot, and destination.

standalone. A machine in the network installation environment that accesses all required resources locally.

standalone shell. A limited version of the shell program used for system maintenance.

standalone system. See standalone workstation.

standalone workstation. A workstation that can perform tasks without being connected to other resources such as servers or host systems.

standard error (STDERR). The place where many programs place error messages.

standard input (STDIN). The primary source of data going into a command. Standard input comes from the keyboard unless redirection or piping is used, in which case standard input can be from a file or the output from another command.

Standard I/O Board. The Standard I/O Board provides a group of I/O functions that are basic to most system units. Common standard I/O functions are keyboard, tablet, speaker, mouse, serial port, parallel port and diskette adapter.

standard output (STDOUT). The primary destination of data coming from a command. Standard output goes to the display unless redirection or piping is used, in which case standard output can be to a file or another command.

standard screen. In the extended curses library, a memory image of the screen to which the routines make changes.

standout mode. The general-purpose highlighting mechanism used by the terminfo structure.

stanza. A group of lines in a file that together have a common function or define a part of the system. Stanzas are usually separated by blank lines or colons, and each stanza has a name.

start method. Takes the device from the stopped state to the available state. The start method applies only to devices that support the optional stopped state.

start-stop. Asynchronous transmission in which a group of signals representing a character is preceded by a start element and followed by a stop element. See also asynchronous transmission.

startup set. A grouping of application servers that can be thought of as a single unit for administration purposes.

state. (1.) A state in which the circuit remains until application of a suitable pulse. (2.) One of the separate, restartable portions into which the runacct command (the main daily accounting shell procedure) breaks its processing. (3.) In SOM, the data (attributes, instance variables and their values) associated with an object. See also behavior.

state information. Information about the current state of the appearance and behavior of a widget or gadget. This information is recorded within each individual widget and gadget and updated as necessary.

state instrument. In Performance Toolbox, a state instrument shows the latest statistics for a system resource, optionally as a weighted average. While it does not show the statistics over time, some state instruments collect this data in case you want to change the instrument to a recording instrument. Types of graphs used to plot these recordings include state bar, state light, pie chart, and speedometer. Contrast with recording instrument.

statement. (1.) An instruction in a program or procedure. (2.) In programming languages, a language construct that represents a step in a sequence of actions or a set of declarations. See also block statement. In Ada language, a statement specifies one or more actions to be performed during the execution of a program.

statement function. In FORTRAN, a name, followed by a list of dummy arguments, that is equated to an arithmetic, logical, or character expression, and that can be substituted for the expression throughout the program. See also macro.

statement function definition. In FORTRAN, a statement that defines a statement function. Its form is a statement function followed by = (equal sign) followed by an arithmetic, logical, or character expression.

statement label. In FORTRAN, a number containing one to five decimal digits that is used to identify a statement. A statement label is usually used to transfer control, define the range of a DO loop, or refer to a FORMAT statement. See also label.

statement number. See statement label.

static. (1.) A style of creating pop-ups. (2.) In C++, a keyword used for defining the scope and linkage of variables and functions. For internal variables, the variable has block scope and retains its value between function calls. For external values, the variable has file scope and retains its value within the source file. For class variables, the variable is shared by all objects of the class and retains its value within the entire program.

static binding. Binding that occurs at compilation time based on the resolution of overloaded functions.

static debugger trap (SDT). A trap instruction placed in a predefined point in code that calls the debug program. The trap instruction causes a program check when run and, as a result of the program check, the debug program is activated.

static display. In text formatting, when the nroff command finds a block of text in the input file that has been specified as a static display, it places the text on the current page only if there is room for the entire block. If there is not enough room, the nroff command starts a new page and places the block of text there. See also floating display.

static linking. Linking of a program in which library procedures are incorporated into the load module, instead of being dynamically loaded from their library each time the program is run.

static memory. Allocated memory of fixed size.

static method. In SOM, any methodthat can be accessed through offset method resolution. Any method declared in the IDL specification of a class is a static method. See also method and dynamic method.

static routing. A method of setting paths between hosts, networks, or both by manually entering routes into the routing table. Static routes are not affected by routing daemons and must be updated manually.

static variable. A variable that is allocated as soon as a program starts running and that remains allocated until the program stops. Normal scoping rules apply to the variable. Contrast with automatic variable.

station. (1.) A computer or device that can send or receive data. (2.) An input or output point of a system that uses telecommunication facilities, such as one or more systems, computers, workstations, devices, and associated programs at a particular location that can send or receive data over a telecommunication line. (3.) A location on a device at which an operation is performed. (4.) In FDDI, an addressable logical and physical attachment in a ring capable of transmitting, receiving, and repeating information. (5.) In SNA, a link station.

statistic line. In Performance Toolbox, the lines in a list that represent a specific value. Contrast with context line.

status. (1.) The current condition or state of a program or device. For example, the status of a printer. (2.) The condition of the hardware or software, usually represented in a status code. (3.) In Enhanced X-Windows, many Xlib subroutines return a success status. If the subroutine does not succeed, however, its values are not disturbed.

STDERR. See standard error.

STDIN. See standard input.

STDOUT. See standard output.

steal (a page frame). The act (by the Virtual Memory Manager) of reallocating a real-memory page frame that contains a virtual-memory page that is being used by a currently executing program.

sticky bit. An access permission bit that causes an executable program to remain on the swap area of the disk. Only someone with root authority can set the sticky bit. This bit is also used on directories to indicate that only file owners can link or unlink files in that directory.

stipple. A bitmap used to tile a region. A stipple pattern serves as an additional clip mask for a fill operation with the foreground color.

stop bit. (1.) In start-stop transmission, a signal at the end of a character that prepares the receiving device for reception of a subsequent character. (2.) A signal to a receiving mechanism to wait for the next signal.

stop method. Takes the device from the available state to the stopped state. The stop method applies only to devices that support the optional stopped state.

stop record. In Performance Toolbox, a special type of value record which signals that recording was stopped for a set of statistics and gives the time it happened. This allows programs using the recording file to distinguish between gaps in the recording and variances in the recording interval.

stopped state. Allows a device to be made unavailable but still have its device driver loaded and bound in the kernel and still be known by the device driver.

storage. (1.) The location of saved information. (2.) In contrast to memory, the saving of information on physical devices such as disk or tape. See also memory. (3.) A unit into which recorded text can be entered, retained, and processed, and from which it can be retrieved. (4.) The action of placing data into a storage device.

storage class specifier. A storage class keyword. One of the following C++ keywords: auto, register, static, or extern.

storage device. (1.) A functional unit for storing and retrieving data. (2.) A facility into which data can be retained.

store. To place information in a storage device (in memory or onto a diskette, fixed disk, or tape), so that it is available for retrieval and updating.

stream. (1.) Sequential input or output from an open file descriptor. (2.) A continuous stream of data elements being transmitted, or intended for transmission, using a defined format. (3.) All data transmitted through a data channel in a single read or write operation. Synonym for data stream. (4.) The kernel aggregate created by connecting STREAMS components, resulting from an application of the STREAM mechanism. The primary components are a stream head, a driver, and zero or more pushable modules between the stream head and driver. A stream forms a full duplex processing and data transfer path in the kernel, between a user process and a driver. A stream is analogous to a shell pipeline except that data flow and processing are bidirectional.

stream buffer. A C++ stream buffer is a buffer between the ultimate consumer and the I/O Stream Library functions that format data. It is implemented in the I/O Stream Library by the streambuf class and the classes derived from streambuf.

stream collection. A method of collecting auditing data that writes audit records to a circular buffer within the kernel. The data can be displayed, or printed to provide a paper audit trail, or converted into bin records.

stream editor. The sed command, which modifies lines from a specified file, according to an edit script, and writes them to a standard output.

stream end. The end of the stream furthest from the user process. The stream end contains the driver.

stream head. The end of the stream closest to the user process. The stream head provides the interface between the stream and the user process. The principal functions of the stream head are processing STREAMS-related system calls, and bidirectional transfer of data and information between a user process and messages in STREAMS' kernel space.

streaming tape device. See streaming tape drive.

streaming tape drive. A magnetic tape unit that stores large amounts of data and is designed to make a nonstop dump or restore of magnetic disks without using interblock gaps.

STREAMS. A kernel mechanism that supports development of network services and data communication drivers. It defines interface standards for character input and output within the kernel, and between the kernel and user level. The STREAMS mechanism comprises integral functions, utility routines, kernel facilities, and a set of structures.

strength reduction. An optimization that replaces an arithmetic operation with a functionally equivalent arithmetic optimization of lesser strength. For example, 4*2 can be transformed into 4+4.

strict type checking. Checking data types for compliance with the rules of C language more strictly than the C compiler, such as with the lint program.

stride. The relationship between the layout of an array's elements in memory and the order in which those elements are accessed. A stride of 1 means that memory-adjacent array elements are accessed on successive iterations of an array-processing loop. A stride of N means that for each array element accessed, N-1 memory-adjacent elements are skipped over before the next accessed element.

string. (1.) A linear sequence of entities such as characters or physical elements. Examples of strings are alphabetic string, binary element string, bit string, character string, search string, and symbol string. (2.) In Pascal, an object of the predefined type STRING. (3.) The form of data used in programming languages for storing and manipulating text. In C language code, a string is treated as a one-dimensional array of type char.

string constant. Characters enclosed in double quotation marks.

string register. A register that holds a defined string value to be called by a token. See also token.

string value. Value of specified string. In AIXwindows, the value of a string that identifies a Text widget.

stroke text. Synonym for programmable character set and geometric text.

structure. A variable that contains an ordered group of data objects. Unlike an array, the data objects within a structure can have varied data types.

Structure Rule Table (SRT). A recurring attribute of the directory schema with the description of the permitted structures of distinguished names.

structure tag. The identifier that names a structure data type.

structured field. A mechanism that permits variable length data to be encoded for transmission in the data stream. See also field.

structured file. (1.) A special type of INed file that contains specialized data, such as information about the structure of the data in the file, and history information about changes that have been made to the file. Structured files can contain hierarchical data that is displayed and edited by using forms. (2.) In Encina, a file with data organized into a specific format that is usually record-oriented.

structured file system. The collection of data managed by a single structured file server (SFS). All access to a structured file system is through a single server, using a special type of file descriptor (OFD) that identifies the file system and its organization.

structured programming. A technique for organizing computer programs in hierarchical modules, making programs easier to debug, modify, and replace. Typically, all modules have a single entry point and a single exit point. Control is passed downward through the structure without unconditional branches to higher levels of the structure.

structured type. Any of several data types that define variables having multiple values; for example, records and arrays. Each value is a component of the structured type. Contrast with scalar type.

stub. (1.) In NCS, a program module that transfers remote procedure calls and responses between a client and a server. Stubs perform marshalling, unmarshalling, and data format conversion. Both clients and servers have stubs. The compiler generates client and server stub code from an interface definition. See also marshal. (2.) Hooking functions used as extensions to the protocol to generate protocol requests for Enhanced X-Windows. Synonym for hooking routines. (3.) The RPC calls produced by the compiler when an interface is defined. Two sets of stubs are produced, client stubs and server stubs. The application code calls the stub, and the RPC mechanism translates this into a call to the appropriate function on the remote machine.

stub procedures. Method procedures in the implementation template generated by the SOM Compiler. They are procedures whose bodies are largely vacuous, to be filled in by the implementor.

Style Manager. In CDE, the software application used to customize some of the visual elements and system device behaviors of the workspace environment, including colors and fonts, and keyboard, mouse, window, and session start-up behaviors.

stylus. A device used to select a particular location on a tablet.

subaddress. In X.25 communications, the unallocated digits at the end of the national terminal number (NTN). If the network provider allocates all digits to the NTN, there can be no subaddress.

subarea node. In data communications, a node that uses network addresses for routing, and whose routing tables are affected by changes in the configuration of the network. Subarea nodes can provide boundary function support for peripheral nodes.

subchannel. A logical communications path defined in S/370 architecture to perform transfers to a given device.

subclass. (1.) A class of widgets that inherits resources from a higher class. (2.) In SOM, a class that inherits instance methods, attributes, and instance variablesdirectly from another class, called the parent class, base class, superclass, or indirectly from an ancestor class. A subclass may also be called a child class or derived class.

subclassing. In SOM, the process whereby a new class, as it is created (or derived), inherits instance methods, attributes, and instance variables from one or more previously defined ancestor classes. The immediate parent class(es) of a new class must be specified in the class's interface declaration. See also inheritance.

subcommand. A request for an operation that is within the scope of work requested by a previously issued command.

subcomponent. In Ada language, either a component, or a component of another subcomponent.

subdirectory. In the file system hierarchy, a directory contained within another directory.

subfolder. In CDE, a folder contained within another folder (sometimes called the parent folder). When discussing command-line activities, this may be called a subdirectory.

subheap. In Pascal, part of a heap delimited by a call to MARK. Subheaps are treated in a stack-like manner within a heap.

subhost. A communications system that controls attached workstations in addition to communicating with another (usually higher-level) system.

subject identifier (SID). A string that identifies a user or set of users. Each SID consists of three fields in the form person.group.organization. In an account, each field must have a specific value; in a ACL entry, one or more fields may be a wildcard.

submenu. A menu accessed from another menu by a --> symbol. A related menu that can only be reached from a main menu. In AIXwindows, one example of a submenu is an XmCascadeMenu widget that appears from the side of an XmPopupMenu widget when the mouse pointer is dragged sideways across a main menu item.

subnet. One of a group of multiple logical network divisions of a single network, such as can be created by the TCP/IP Interface Program. Synonymous with subnetwork.

subnet address. The subdivided part of the local host address, which has been reserved for indicating the subnet. Subnet addressing allows an autonomous system made up of multiple networks to share the same Internet network address.

subnet address mask. A bit mask used by a local system to determine whether a destination is on the same network as the source or if the destination can be reached directly through one of the local interfaces.

subnetwork. Synonym for subnet.

subobject. An object that is in a subordinate relationship to a given object.

subpanel. In CDE, an extension of the Front Panel that slides up providing access to additional elements. Subpanels usually contain groups of related elements.

subpattern. A discrete element of a regular expression.

subprocess. A process initiated by another process. Control is transferred back to the main process after the subprocess finishes running.

subprogram. (1.) A program called by another program, such as a subshell. (2.) In FORTRAN, a program unit that has a FUNCTION, SUBROUTINE, or BLOCK DATA statement as its first statement. Contrast with main program. (3.) In Ada language, a subprogram is either a procedure or a function. A procedure specifies a sequence of actions and is invoked by a procedure call statement. A function specifies a sequence of actions and also returns a value called the result, and so a function call is an expression. A subprogram is written as a subprogram declaration, which specifies its name, formal parameters, and (for a function) its result; and a subprogram body which specifies the sequence of actions. The subprogram call specifies the actual parameters that are to be associated with the formal parameters. A subprogram is one of the kinds of program unit. See also function and procedure.

subrange scalar type. In Pascal, a type that defines a variable whose value is restricted to some subset of values of a base scalar type. See also base scalar type.

subroutine. (1.) A sequenced set of statements or coded instructions that can be used in one or more computer programs and at one or more points in a computer program. (2.) A routine that can be part of another routine. See also routine. (3.) A request by an active process for a service by the system kernel. See also macro.

Subroutine ID. A unique identification number associated with each subroutine included in an application.

subroutine switch table. Contains the address for the specific handler routine that handles the subroutine.

subscribe. In X.25 communications, to a rent an X.25 line, specifying the required facilities.

subscript. (1.) An integer or variable whose value selects a particular element in a table or an array. (2.) Characters printed one-half line below the normal printing line.

subscript declarator. In an array definition or declaration, the bracketed expressions following the array name. Specifies the number of elements in an array dimension.

subscript quantity. In FORTRAN, a component of a subscript. A subscript quantity is an integer or real constant, variable, or expression.

subserver. A system resource or program that is directly controlled by a server program running under control of the System Program Controller.

subset. (1.) A set each element of which is an element of a specified other set. (2.) A variant form of a programming language with fewer features or more restrictions than the original language. (3.) In telecommunications, a subscriber set such as a telephone.

subshell. An instance of the shell program started from an existing shell program.

substring. A contiguous subportion of a string.

subsystem. (1.) A secondary or subordinate system, usually capable of operating independently or synchronously with a controlling system. (2.) The part of communications that handles the requirements of the remote system, isolating most system-dependent considerations from the application program.

subtree. A lower-level directory structure.

subtype. (1.) An IOCINFO ioctl variable that identifies the kind of DLC being queried. (2.) In Ada language, a subtype of a type characterizes a subset of the values of the type. The subset is determined by a constraint on the type. Each value in the set of values of a subtype belongs to the subtype and satisfies the constraint determining the subtype.

subunit. For Ada programming, see body.

subwidget. In AIXwindows and Enhanced X-Windows, a widget class directly beneath a higher widget class in a widget-gadget hierarchy.

suffix. (1.) A character string attached to the end of a file name that helps identify its file type. (2.) A code dialed by a caller who is already engaged in a call. (3.) A part of a file name, added at the end, separated from other suffixes or the base file name by some punctuation, such as a period (.).

superblock. In a file system layout, refers to Block 1, which is used to keep track of the file system and is the most critical part of the file system. It contains information about every allocation or deallocation of a block in the file system. See also i-list.

superclass. In AIXwindows and Enhanced X-Windows, a class of widgets that passes inheritable resources down the hierarchy to a lower subclass. See also widget record.

superclient. A diskless client with read and write permission and root access to the remote resources used by other clients. A superclient installs and maintains optional software of Version 3.2 of the operating system on a non-Version 3.2 diskless server.

superobject. An object that is in a superior relationship to a given object.

superscalar. The capability to execute multiple instructions in a given clock cycle.

superuser. See root user.

superuser authority. See root user authority.

supervisor. The part of the operating system control program that coordinates the use of resources, and maintains the flow of processing unit operations.

supervisor call (SVC). An instruction that interrupts the program being run and passes control to the supervisor so it can perform a specific service indicated by the instruction.

supporters. In Ada language, all the compilation units required by the language to allow a unit to be compiled. This consists of the unit's imports, their imports, and so on.

surface characteristics. Characteristics of the style of a written document: readability, sentence length and structure, word length and usage, verb type, and sentence openers.

suspended state. (1.) A state in which the resource is temporarily not receiving a request. A start action request returns the resource to the state it was in prior to being suspended. (2.) A software state in which a task is not dispatched by the system and is not contending for the processor.

SVC. See switched virtual circuit and Supervisor call.

swap interval. In GL, the amount of elapsed time between frame buffer swaps. The system waits at least the amount of time specified by the swap interval subroutine before honoring a request to exchange the front and back buffers. The swap interval is measured in units of vertical retraces, which occur every 30th of a second on most systems. The swap interval is useful in achieving smooth-flowing animation.

swapping. (1.) 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. (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.

swidget. See shadow widget.

switch. A command-line option.

switch expression. (1.) The expression that is located between the keyword switch and the body of a switch statement. (2.) In C language, the controlling expression of a switch statement.

switch table. The table used by the file system to locate the entry points of a character device.

switched line. In data communications, a connection between computers or devices established by dialing. Contrast with nonswitched line.

switched network backup (SNBU). In data communications, a technique that provides a switched line connection when a nonswitched line fails.

switched virtual circuit (SVC). In X.25 communications, a virtual circuit that is requested by a virtual call. It is released when the virtual call is cleared. Contrast with permanent virtual circuit. See also virtual circuit.

SWVPD. See Software Vital Product Data.

symbol. In the SOM Emitter Framework, any of a (standard or user-defined) set of names (such as, className) that are used as placeholders when building a text template to pattern the desired emitter output. When a template is emitted, the symbols are replaced with their corresponding values from the emitter's symbol table. Other symbols (such as, classSN) have values that are used by section-emitting methods to identify major sections of the template (which are correspondingly labeled as "classS" or by a user-defined name).

symbol table. See parse.

symbolic address. A unique line address, such as . (period) or $ (dollar sign), used in place of a line number address to identify location of data. See also pattern address.

symbolic debugger (sdb). A tool that aids in the debugging of programs written in certain high-level languages.

symbolic link. Type of file that contains the path name of and acts as a pointer to another file or directory.

symbolic name. A unique name used to represent an entity such as a file or a data item. See also name.

symmetrical multiprocessor (SMP) system. A system containing multiple processors that are essentially identical and perform identical functions.

SYN. See synchronization character.

synchronization character (SYN). In binary synchronous communications, the transmission control character that provides a signal to the receiving station for timing.

synchronous. (1.) Two or more processes that depend upon the occurrences of specific events such as common timing signals. (2.) Occurring with a regular or predictable time relationship or sequence.

synchronous data link control (SDLC). (1.) A form of communications line control using commands to control the transfer of data over a communications line. Contrast with binary synchronous communication. (2.) A discipline conforming to subsets of the advanced data communications control procedures (ADCCP) of the ANSI and the HDLC of the International Organization for Standardization. It manages synchronous, code-transparent, serial-by-bit information transfer over a link connection. Transmission exchanges can be duplex or half-duplex over switched or nonswitched links. The configuration of the link connection may be point-to-point, multipoint, or loop.

synchronous transmission. (1.) In data communications, a method of transmission in which the sending and receiving of characters is controlled by timing signals. Contrast with asynchronous transmission. (2.) Data transmission in which the time of occurrence of each signal representing a bit is related to a fixed time base.

syntax. (1.) The grammatical rules for constructing a command, statement, or program. (2.) In XOM: (a.) An OM syntax is any of various categories into which the object management specification statically groups values on the basis of their form. These categories are additional to the OM type of the value. (b.) A category into which an attribute value is placed on the basis of its form.

syntax diagram. A diagram for a command that displays how to enter the command on the command line.

syntax error. A compile-time error caused by incorrect syntax. See also semantic error.

syntax template. A lexical construct containing an asterisk from which several attribute syntaxes can be derived by substituting text for the asterisk.

system. The computer and its associated devices and programs.

System/370 Host Interface Adapter (HIA). An adapter that allows the attachment of a POWERstation or POWERserver to a 5088 Graphics Control Unit.

system address list. The address list, controlled by the system manager, that all users on the system can use with the xtalk command to make outgoing X.25 calls. See also address list and user address list.

System Application Architecture FORTRAN (SAA FORTRAN). A superset of the ANSI X3.p - 1978 FORTRAN 77 standard.

system board. The main circuit board in the system unit that supports a variety of basic system devices, such as a keyboard, a mouse, and so forth. The system board also supplies other basic system functions.

system call. A call by a program to an operating system subroutine.

system console. A console, usually equipped with a keyboard and display screen, that is used by an operator to control and communicate with a system. Synonymous with console.

system customization. Specifying the devices, programs, and users for a particular data processing system. Contrast with configuration. See also customization.

system date. The date assigned by the system user during setup and maintained by the system. See creation date and session date.

system dump. A copy from storage of selected data areas. Synonymous with kernel dump.

system image. The representation of a program (and its related data) as it exists at the time it resides in system memory.

system management. The tasks involved in maintaining the system in good working order and modifying the system to meet changing requirements.

System Management Interface Tool (SMIT). A set of menu-driven services that facilitate the performance of such system tasks as software installation and configuration, device configuration and management, problem determination, and storage management. SMIT is provided in both a character-based curses interface and an AIXwindows-based graphical user interface.

system memory. Synonymous with main storage, but used in hardware to refer to semiconductor memory (modules).

system menu. In AIXwindows, the pulldown in the top left-hand corner of a window that allows users to restore, move, size, minimize, and maximize the window. It also allows users to exit the application or to close a window. Also causes the appearance of a dialog box to contain a list of the active applications. With the optional split window technique, the user views many parts of the same object at one time.

System Network Architecture (SNA). (1.) An architecture for controlling the transfer of information in a data communications network. (2.) The description of the logical structure, formats, protocols, and operating sequences for transmitting information units through, and controlling the configuration and operation of networks.

system node. In the hierarchy of device locations, this is the highest node. Every hardware device will lead back to the system node if you follow the connection path. For example, an SCSI disk is connected to an SCSI adapter that is connected to a bus that is connected to the system node.

System Object Model (SOM). Object-oriented programming technology for building, packaging, and manipulating binary class libraries.

system parameters. Synonym for kernel parameters.

System Performance Measurement Interface (Spmi). In the Performance Toolbox, the Agent API that allows an application program to register custom performance statistics about its own performance or that of some other system component. Once registered, the custom statistics become available to any consumer of statistics, local or remote. Also permits applications to access statistics on the local system without using the network interface. Such applications are called local data-consumer programs.

system profile. A file containing the default values used in system operations.

System Program Controller (SPC). A system program that controls the operation of other application programs that run in the background (daemons).

system prompt. Synonym for command line. The system prompt is the symbol that appears at the command line of an operating system. The system prompt indicates that the operating system is ready for the user to enter a command.

System Resource Controller (SRC). A set of commands and subroutines used to create and control subsystems. The SRC controls subsystem processes using a common command line and the C interface. The SRC is useful when you need a common method to start, stop, and collect status information on processes.

system restart. Synonym for initial program load.

system ROS. The piece of system microcode that is responsible for loading a boot image.

system services control point (SSCP). In SNA, the focal point within an SNA network for managing the configuration, coordinating network operator and problem determination requests, and providing directory support and other the session services for network end users. Multiple SSCPs, cooperating as peers, can divide the network into domains of control, with each SSCP having a hierarchical control relationship to the physical units and logical units within its domain.

system startup. Synonym for initial program load.

system time. The amount of time that the operating system spends providing services to an application. System time includes time spent by the operating system allocating storage or devices to your program, and time spent processing operating system calls your program makes.

system unit. The part of the system that contains the processing unit.

system user. A person, device, or system that uses the facilities of a computer system.