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separate compilation:
The compilation of a source module using data representing interface and context relationships from related source modules. Interface and context data are used by the compiler to check validity and to resolve references. Synonymous with dependent compilation.

separating character:
Synonym for information separator.

separation of duties:
In security, dividing responsibility for sensitive information so that no individual acting alone can compromise the security of the data processing system.

(1) A delimiter that prevents adjacent lexical tokens or syntactic units from being interpreted as a single item; for example, the space character or format effectors. Contrast with delimiter. (2) Deprecated synonym for delimiter.

A byte that consists of seven bits. Synonymous with 7-bit byte.

(1) To place items in an arrangement in accordance with the natural numbers. Methods or procedures may be specified for mapping other natural linear orders onto the natural numbers; then, by extension, sequencing may be, for example, alphabetic or chronological. (2) A set of items that have been sequenced.

sequencing key:
Synonym for sort key.

Pertaining to a process consisting of multiple subprocesses that are executed in such a manner that every one but the first one follows immediately after its preceding one finishes. The subprocesses are also said to be sequential. A sequential process is an example of a serial process. Contrast with consecutive.

sequential access:
The capability to enter data into a storage device or retrieve data from a storage device or a data medium in the same sequence as the data is ordered. Synonymous with serial access.

sequential access storage:
A storage device that provides only sequential access to data.

sequential batch processing:
A mode of operating a computer in which a run must be completed before another run can be started.

sequential circuit:
A logic circuit whose output values, at a given instant, depend upon its input values and the internal state at that instant, and whose internal state depends upon the immediately preceding input values and the preceding internal state. A sequential circuit can assume a finite number of internal states. Contrast with combinational circuit.

sequential cohesion:
Cohesion in which the result of one activity of a module serves as an operand for another subsequent activity performed by the same module.

sequential file:
A file in which records are ordered according to the values of one or more key fields, and processed in the same sequence from the beginning of the file.

sequential logic element:
A device that has at least one output channel and one or more input channels, all characterized by discrete states, such that the state of each output channel is determined by the previous states of the input channels.

sequential search:
Synonym for linear search.

(1) Pertaining to a process in which all subprocesses under consideration are executed one after the other; for example: the serial transmission of the bits of a character, a sequential process. (2) Pertaining to the sequential or consecutive occurrence of two or more related activities in a single device or channel. (3) Pertaining to the sequential processing of the individual parts of a whole, such as the bits of a character or the characters of a word, using the same facilities for successive parts. Contrast with parallel.

serial access:
Synonym for sequential access.

serial computer:
A computer that has a single arithmetic and logic unit. Contrast with parallel computer.

Serial Line Internet Protocol (SLIP):
An early version of a protocol designed to permit the transfer of IP packets over a dial-up connection. It is now largely replaced by the Point-to-Point Protocol (PPP).

Synonym for parallel-serial converter.

serial mouse:
A mouse that is connected directly to a serial port of a computer.

serial number:
An integer denoting the position of an item in a sequence.

serial operation:
Pertaining to the sequential or consecutive execution of two or more operations in a single device such as an arithmetic and logic unit. Contrast with parallel operation.

serial-parallel converter:
A functional unit for converting a sequence of consecutive signal elements into a corresponding group of signal elements all presented simultaneously, which represents the same information. Synonymous with deserializer.

serial port:
A port of a functional unit used to transfer one bit at a time.

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

serial sort:
A sort that requires only sequential access to the items in a set.

serial transmission:
The sequential transmission over one transmission channel of the signal elements of a group representing a character or other entity of data.

A measure of the ability of a service to be obtained at the request of the user, and to continue to be provided for a requested duration within specific tolerances and under given conditions. Availability is an instantaneous concept, whereas servability is availability over a period of time.

In a computer network, a functional unit that provides services to workstations, to personal computers or to other functional units; for example: a file server, a print server, a mail server. Services may be dedicated services or shared services.

In OSI, a capability of a given layer and the layers below it that is provided to the entities of the next higher layer. The service of a given layer is provided at the boundary between this layer and the next higher layer. (Figure 47 - The Open Systems Interconnection Reference Model).

Synonym for maintainability.

service access point (SAP):
In OSI, the point at which the services of a given layer are provided by an entity of that layer to an entity of the next higher layer.

service bit:
Synonym for overhead bit.

service data unit (SDU):
In OSI, a set of data that is sent by a user of the services of a given layer and that must be transmitted to the peer service user semantically unchanged. (Figure 54 - Data units in OSI layers).

service primitive:
Synonym for primitive.

service provider:
(1) In OSI, an abstract representation of an entity that provides a service to peer service users, such as the transport services between such service users. (2) In networking, an organization that provides services for content providers or for users of a computer network; for example, an Internet Service Provider (ISP). The services may be: access to the computer network, content hosting, news server, server of a private message handling system, etc.

service user:
In OSI, an entity in a single open system that makes use of a service through service access points.

All the activities that take place during the establishment, maintenance, and release of a logical connection in a computer network.

session layer:
In OSI, the layer that provides the means necessary for cooperating entities from the presentation layer to organize and synchronize their dialogue and to manage their data exchange. (Figure 47 - The Open Systems Interconnection Reference Model).

In a network data model, a named collection of records in accordance with a corresponding set type.

set a breakpoint:
To define both a breakpoint and an appropriate event that suspends execution of a program.

set a counter:
To cause a counter to take the state corresponding to a specified number.

set occurrence:
In the CODASYL model, an occurrence of an owner record together with zero or more occurrences of its member records.

In artificial intelligence, the specific context of a script including props and thematic roles.

settling time:
Following the initiation of a specified input signal to a system, the time required for the output signal to enter and remain within a specified narrow range centered on its steady-state value. The input may be a step, impulse, ramp, parabola, or sinusoid. For a step or impulse, the range is often specified as ± 2% of the final steady-state value.

set type:
In a network data model, a named collection of record types that consist of one record type of an owner record and one or more record types of member records, together with a hierarchical relationship between the record type of the owner record and the other record types.

sex changer:
Synonym for gender changer.

A byte that consists of six bits. Synonymous with 6-bit byte.

A standard language for tagging elements of documents to permit special handling such as indexing, formatting, and linking. The standard is ISO/IEC 8879 Ed. 1.0 b -- Title: Information Processing -- Text and Office Systems - Standard Generalized Markup Language (SGML).

synchronous graphic random access memory.


(1) In computer graphics, a technique for rendering an object by calculating the intensity of light on its surface, based on how the light sources are positioned and how they illuminate the object. (2) In computer graphics, a luminance gradient in an image, not present in the original scene but caused by the vision system.

shannon (Sh):
A unit of logarithmic measure of information expressed as a logarithm to base 2; for example, the decision content of a character set of eight characters equals 3 shannon. Due to its theoretical relationship to the number of yes and no questions required to achieve the search results, the shannon is commonly referred to as a bit. Note that shannon is a binary unit of information as distinct from a bit that is a binary digit used in data representation. Under certain ideal conditions they are numerically equal, however, due to noise and other problems, the measure of information is generally less than the corresponding value of the measure of data in bits. Contrast with hartley, natural unit.

shape-acquisition camera:
A camera in a pattern recognition system that enables that system to recognize changes of shapes, such as, facial expression.

shape from contour:
The inference of information about an object surface using contours derived from an image.

shape from texture:
The inference of information about the surface properties of an object based upon the analysis of texture variations.

shared data:
Data that can be accessed by two or more modules that may be executed asynchronously or concurrently; for example, COMMON in Fortran, "compool" in some programming languages, PL/I single variables tagged EXTERNAL, a form of a package in Ada.

shared variable:
A variable that can be accessed by two or more asynchronous procedures or concurrently executed programs.

Software that is distributed without a licensing fee, but for which a nominal payment is requested for continued use.

sheet-fed scanner:
A scanner that can automatically load a series of documents for scanning.

(1) An empty expert system structure into which a particular field of expertise is built. Synonymous with expert system shell. (2) 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. Shells simplify user interactions by eliminating the user's concern with operating system requirements. A computer may have several layers of shells for various levels of user interaction. (3) Software that allows a kernel to run under different operating system environments.

shell site:
Synonym for cold site.

In computer graphics, suppression of all display elements that lie within a given clip mask. Synonymous with reverse clipping.

The movement of some or all of the characters of a word, each by the same number of character positions in the direction of a specified end of the word.

shift-in character (SI):
A code extension character that is used to terminate a sequence that has been introduced by the shift-out character and returns to the interpretation of the standard character set.

shift-out character (SO):
A code extension character that is used to start a sequence of characters with alternate interpretation; the sequence is terminated with a shift-in character.

shift register:
A register in which all bits are moved a fixed number of bit positions at each clock cycle. Shifts may result in loss of data or the movement of data from one end of the register to the other end, in a circular fashion.

short card:
An expansion board that is shorter than a full length circuit board. Synonymous with half card.

To reduce the size of a window.

Image transformation that reduces the size of an image.

shutter goggles:
Synonym for electronic shutter glasses.

The shift-in character.

In computer vision, one of two or more blobs that are children of the same parent; for example, the stars in the blue rectangle of the U.S. flag are siblings of each other.

side effect:
Any indirect consequence caused by the execution of an expression, statement, or subprogram. Side effects may be intended, for example, to change the data value of a parameter passed to a function.

sifting sort:
Synonym for bubble sort.

sigma memory:
A storage device in a calculator used to accumulate the results of a series of calculations.

A physical phenomenon whose presence, absence, or variation represents data.

signal element:
A part of a signal distinguished by its nature, magnitude, duration, transition, or relative position; for example: signal transition, significant instant, significant interval. The waveform could represent amplitude, frequency, or relative phase of any phenomenon, such as voltage, light energy, or acoustic energy. (Figure 21 - Components of an idealized discrete signal).

In communication networks, any of the signal exchanges associated with establishing and maintaining connections as supporting functions but not including actual user data exchange. Signaling includes establishing a route, control of the physical and logical circuit, clearing the connection, and billing. Signaling may be accomplished using circuits and protocols different than those used for the actual exchange of user data.

signal regeneration:
Use of an incoming signal as the basis for generation of an equivalent outgoing signal whose characteristics better conform to the design or standards for such signals.

signal shaping:
The action of modifying one or more characteristics of a signal, such as the maximum value, shape, or timing of the successive elements constituting the signal.

(1) The observable or characteristic measurement or feature pattern derived from entities of a particular category; for example, the feature pattern that determines the particular class of entities. (2) In electronic mail, at the end of the body, a specific piece of text designed by the originator for individual identification. The signature usually contains name, address, and may also include telephone and fax numbers. The signature may include a digital signature or other data authenticating the message.

sign bit:
A bit that occupies a sign position and indicates the algebraic sign of the number represented.

sign change function:
The function that allows a reversal of the sign of a number held in a calculator.

sign character:
A character that occupies a sign position and indicates the algebraic sign of the number represented.

significant condition:
A characteristic quantity of a signal element defining the meaning of that signal element in accordance with a code. (Figure 21 - Components of an idealized discrete signal).

significant digit:
In a numeral, a digit that is needed to preserve a given accuracy or a given precision.

significant digit arithmetic:
A method of making calculations by the use of a modified form of a floating-point representation system in which the number of significant digits in the result is determined with reference to the number of significant digits in the operands, the operation performed, and the degree of precision available.

significant instant:
In a digital signal, an instant at which a signal element commences. (Figure 21 - Components of an idealized discrete signal).

significant interval:
The time interval between two consecutive significant instants. (Figure 21 - Components of an idealized discrete signal).

sign position:
A position, normally located at one end of a numeral, that contains an indicator denoting the algebraic sign of the number represented.

SIMD processor:
A parallel processor where many functional units perform the same operation on different data; for example, an array processor. SIMD processor is the abbreviation for single instruction - multiple data processor.

similarity-based generalization:
A concept generalization that describes all examples of a given concept by exploring similarities and differences between these examples.

Simple Mail Transfer Protocol:

simple statement:
In programming, a statement that encloses no other statement.

simple type:
In Pascal, the term for scalar type.

simplex transmission:
Data transmission in one preassigned direction only.

To represent certain features of the behavior of a physical or abstract system by the behavior of another system; for example, to represent a physical phenomenon by means of operations performed by a computer or to represent the operations of a computer by those of another computer. Contrast with emulate.

The use of a data processing system to represent selected behavioral characteristics of a physical or abstract system; for example: the representation of air streams around airfoils at various velocities, temperatures, and air pressures.

A functional unit that represents certain features of the behavior of a physical or abstract system.

(1) Pertaining to events that occur at the same instant of time. (2) Pertaining to processes that are executed within a common interval of time, each one by a separate functional unit; for example: computing, printing, and displaying in the execution of one or more programs. Contrast with concurrent. See also interleave.

simultaneous contrast:
The visual illusion that makes a region of an image appear brighter or darker depending upon the surrounding luminance.

single-address instruction:
Synonym for one-address instruction.

single-cable broadband LAN:
A broadband LAN that uses one cable for both the forward LAN channel and the backward LAN channel.

single-density disk (SDD):
A floppy disk with the same form and bit density as originally introduced into production. The original 3.5 inch floppy disks had a storage capacity of 360 kilobytes. Synonymous with SD disk.

single instruction - multiple data processor:
SIMD processor.

single-layered network:
In artificial neural networks, a layered network having only source nodes and one output layer, without hidden layers. In a single-layered network, only the output layer performs computation.

single-level device:
In computer security, a functional unit that can only process data of a single security level at a particular time.

Synonym for monomedia.

Characterized by the use of one computer word to represent a number and satisfy the required precision.

single sided/double density (SSDD):
A double-density disk where only one side is used for the recording of data.

Pertaining to a method of operating a computer in which each step is performed in response to a single external signal.

single-step execution:
Synonym for single-step operation.

single-step operation:
A mode of operation of a computer in which a single instruction, or part of an instruction, is executed in response to an external signal. Single-step operation is used in debugging. Synonymous with single-step execution, step-by-step operation.

SI system:
Synonym for speaker-independent system.

six degrees of freedom:
In virtual reality, the six measurements (horizontal, vertical, depth, rotation, yaw, and pitch) that can be assigned to any one movement.

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