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The substitute character.

subband coding:
Speech coding consisting of filtering the signal with a filter bank and then encoding the resulting output signals.

(1) In computer security, an active entity that can access objects; for example, a process that involves execution of a program. A subject may cause information to flow among objects or may change the state of the data processing system. (2) In electronic mail, the part of a heading that summarizes the content of the message as specified by the originator.

In the Open Systems Interconnection Reference Model, a conceptually complete group of services, functions, and protocols that may extend across open systems and that is included in a layer.

In electronic mail, a transmittal step in which a user agent or a message store conveys a message or a probe to a message transfer agent.

Synonym for subnetwork.

A part of a network that has a set of common characteristics among its elements, that has definite limits, and that can be considered as a network itself. Synonymous with subnet.

subordinate station:
In basic mode link control, a data station that is selected by a master station to receive data.

sub-pixel resolution:
A resolution of less than one pixel that is obtained by interpolating.

A module that has an identifier and that is invoked into the control flow from another program or by another module by means of a specific language construct and from which the control flow returns to the invoking program or module.

subprogram call:
A call that invokes a subprogram; for example, procedure-call statement, function call.

subprogram trace:
A record of all or selected subprogram calls performed during the execution of all or part of a program and, optionally, the values of parameters passed to and returned by each subprogram or other module.

Synonym for procedure.

subroutine call:
A language construct, in object code, that performs the call.

A subset of the schema that provides a complete description of a database from the perspective of a specific application. Synonymous with view.

To add one's address to a distribution list or to join a forum.

A user authorized to use one or more services, such as a connection to the Internet, electronic mail, or the electronic version of a newsletter.

A symbol that is associated with the name of a set to identify a particular subset or element of the set.

Referencing an array element by means of an array reference and one or more expressions that, when evaluated, denote the position of the element.

A set, each element of which is an element of another specified set.

substitute character (SUB):
A control character that is used in the place of a character that is recognized to be invalid or in error, or that cannot be represented on a given device.

Encryption that replaces bit strings or character strings with other bit strings or character strings. The resulting ciphertext is called substitution cipher.

A transparent layer of the disk, provided for mechanical support of the recording layer, through which the optical beam accesses the recording layer.

subsymbolic representation:
A technique for knowledge representation that distributes the representation over a relatively large network rather than storing symbols directly. In the connectionist model, the knowledge stored in the network is inherent in the connection weights and cannot easily be expressed as simple rules or symbolic forms.

A secondary or subordinate system, usually capable of operating independently of, or asynchronously with, a controlling system.

subtotal function:
The function that allows the display or printing of an interim result of a calculation.

A functional unit whose output data is a representation of the difference between the numbers represented by its input data.

Any node within a tree with all its connected descendent nodes.

A data type declared from another data type by one or more constraints on that other data type.

The separately compiled body of a module.

suffix notation:
Synonym for postfix notation.

summary punch:
A card punch used to record data that were calculated or summarized by another device.

A functional unit whose output analog variable is equal to the sum, or a weighted sum, of the input analog variables. Synonymous with analog adder.

summing integrator:
A functional unit whose output analog variable is the integral of a weighted sum of the input analog variables with respect to time or with respect to another input analog variable.

Any of the class of computers that have the highest processing speeds and capacity available at a given time.

An oversized sector written on a floppy disk, as part of a method of copy protection.

supervised learning:
A learning strategy in which the correctness of acquired knowledge is tested through feedback from an external knowledge source.

Synonym for supervisory program.

supervisory program:
A program, usually part of an operating system, that controls the execution of other routines and regulates the flow of work in data processing. Synonymous with executive program, supervisor.

To provide the necessary resources for the correct operation of a functional unit.

support program:
Synonym for support software.

support software:
Software or a program that aids in the development, maintenance, or use of other software or provides general application-independent capability; for example, a compiler, a database management system. Synonymous with support program.

In networking, to navigate through a network without having a specific goal in mind. Contrast with browsing.

surface modeling:
A mathematical method for representing solid-appearing objects in a computer-aided design system. Synonymous with surfacing.

Synonym for surface modeling.

surge resistance:
The capability of a device to remain functionally intact after exposure to overvoltages. Synonymous with surge-withstand capability.

surge-withstand capability:
Synonym for surge resistance.

To roll out content of memory to make room for new data and to roll in that data.

The systematic movement that paints an image, such as a raster scan in TV or a radial scan in a weather RADAR.

sweep representation:
Solid modeling of a new object by moving a template through space.

In programming, a choice of one jump from a selection of jumps, controlled by a flag.

The process of temporarily associating functional units, transmission channels, or telecommunication circuits for providing a connection; for example: circuit switching, message switching, packet switching.

switching function:
A function that has only a finite number of possible values and whose independent variables each have only a finite number of possible values.

switching variable:
A variable that may take only a finite number of possible values or states. For example, a character of a character set.

A character string or a bit string in a word.

A graphic representation of a concept that has meaning in a specific context.

symbolic address:
An identifier that represents an address.

symbolic addressing:
A method of addressing in which the address part of an instruction contains a symbolic address.

symbolic coding:
The preparation of routines and programs in a symbolic language.

symbolic execution:
A process that supports the analysis of software by simulating the execution of all or part of a program, using symbols for input data, such as names of variables, rather than actual values, and expressing program outputs as logical or mathematical expressions involving these symbols.

symbolic language:
A programming language that names operations, addresses, operands, and results in symbolic form; for example, assembly language, high-level language.

symbolic logic:
The discipline in which valid argument and operations are dealt with using an artificial language designated to avoid the ambiguities and logical inadequacies of natural languages. Synonymous with mathematical logic.

symbolic trace:
A record of the statements of the source program and the outcome of jumps when the program is executed, using symbolic, rather than actual values for input data.

symbol manipulation:
The processing of symbols without regard for the numeric values of their representations.

symbol string:
A string consisting solely of symbols.

symmetrical list:
A linked list in which each item also contains data for locating the preceding one. Synonymous with bidirectional list.

symmetric binary channel:
In communication theory, a channel that is designed to convey messages consisting of binary characters and that has the property that the conditional probabilities of changing any one binary character to the other binary character are equal.

symmetric cryptography:
Cryptography in which the same key is used for encryption and decryption.

symmetric multiprocessing (SMP):
Multiprocessing that allows the operating system and application code to run on any free processor.

The synchronous idle character.

synaptic connection:
Deprecated synonym for neural connection.

synaptic interconnection:
Deprecated synonym for neural connection.

synaptic weight:
Deprecated synonym for connection weight.

The action of maintaining common timing and coordination of the execution of two or more asynchronous procedures.

synchronization pulses:
Pulses introduced by transmission equipment into the receiving equipment to keep the two equipments operating in step.

Pertaining to two or more processes that proceed within a given time interval and that depend upon the occurrence of specific events such as common timing signals.

synchronous DRAM (SDRAM):
A form of dynamic RAM that can run at higher clock speeds than conventional DRAM by synchronizing itself with the computer's internal clock.

synchronous graphic random access memory (SGRAM):
Dynamic RAM that can synchronize with the computer's clock.

synchronous idle character (SYN):
A transmission control character used in synchronous transmission systems to provide a signal from which synchronization or synchronous correction may be achieved between data terminal equipment, particularly when no other character is being transmitted.

synchronous neural network:
An artificial neural network in which all artificial neurons are simultaneously updated.

synchronous operation:
(1) An operation that occurs regularly or predictably with respect to the occurrence of a specified event in another process; for example, the calling of an input/output routine that receives control at a precoded location in a program. (2) A mode of operation in which each action is started by a clock. Contrast with asynchronous operation.

synchronous time-division multiplexing:
Time division multiplexing in which time slots are assigned to input channels on a predetermined basis. The individual input/output channels may be managed as either synchronous or asynchronous channels.

synchronous transmission:
Data transmission in which the time of occurrence of each signal element is related to a fixed time base.

One of two or more terms that refer to the same entity.

The relationships among symbols or groups of symbols, independent of their meanings or the manner of their interpretation and use; for example, the rules governing the structure of a language. Contrast with semantics.

syntax-directed editor:
A text editor that is designed for a particular programming language and that determines the conformance with the syntax of that programming language.

syntax language:
A metalanguage used to specify or describe the syntax of another language.

In artificial intelligence, techniques for computer-generation of human voice, of written text, and of images from digital, analog, and symbolic input.

synthesis by parametric modeling:
Synonym for synthesis by parametric representation.

synthesis by parametric representation:
A method of speech synthesis that abstracts from the speech signal to a model for speech production based on time and frequency parameters such as formants, pitch, and excitation amplitudes. Unlike direct waveform synthesis, synthesis by parametric representation reduces storage requirements per message.

synthetic speech:
Synonym for artificial speech.

system generation.

A set of elements and relations among them considered as a whole and for which there is a recognized purpose and capability. Such elements may be both material objects and modes of thinking as well as the results thereof (e.g., forms of organization, mathematical methods, and programming languages).

system analysis:
A systematic investigation of a real or planned system to determine the requirements and processes of the system and how these relate to each other and to any other system. Synonymous with systems analysis.

system description:
Documentation that results from system design defining the organization, essential characteristics, and the hardware and software requirements of a system.

system design:
A process of defining the hardware and software architecture, components, modules, interfaces, and data for a system to satisfy specified requirements.

system development:
A process that usually includes requirements analysis, system design, implementation, documentation, and quality assurance.

system documentation:
One or more documents that describe the requirements, capabilities, limitations, design, operation, or maintenance of an information processing system.

system follow-up:
The study of the effects of a system after it has reached a stabilized state of operational use. Synonymous with post-implementation review, post-development review.

system generation (sysgen):
The process of selecting optional parts of an operating system and of creating a particular operating system tailored to the requirements of a data processing installation.

system integration:
The progressive assembling of system components into the whole system.

system integrity:
(1) In data processing, the state that exists when there is complete assurance that, under all conditions, a data processing system is based on the logical correctness of the hardware and software that implement the protection mechanisms, and data integrity. (2) In security, the quality of a data processing system fulfilling its operational purpose while both preventing unauthorized users from making modifications to or use of resources and preventing authorized users from making improper modifications to or improper use of resources.

system library:
A software library that is resident in a data processing system and that can be accessed for use or incorporated into other programs by reference; for example, a macro library, a dynamic-link library.

system life cycle:
The course of developmental changes through which a system passes from its conception to the termination of its use.

system maintenance:
The modification of a system to correct faults, to improve performance, or to adapt the system to a changed environment or changed requirements.

system production time:
That part of operating time that is actually used by some user.

systems analysis:
Synonym for system analysis.

system software:
Application-independent software that supports the running of application software; for example an operating system.

system support:
The continued provision of services and material necessary for the use and improvement of an implemented system.

system test and evaluation plan:
Synonym for test plan.

system test time:
The time during which a functional unit is tested for proper operation. Because a functional unit may consist of a computer and its operating system, system test time in some cases includes the time for testing programs belonging to the operating system.

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