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- erasable programmable logic device (EPLD):
- A programmable logic array designed to perform a user-erasable programmable function.
- erasable programmable read-only memory:
- EPROM.
- erasable storage:
- Storage in which different data can be written successively at the same storage location.
- erase:
- To remove data from a data medium. A true erasure will not only delete the data but will also overwrite it in such a manner that it cannot be retrieved by a later operation. Contrast with delete.
- erase head:
- A magnetic head capable only of erasing data on a magnetic data medium. Synonymous with erasing head.
- erasing head:
- Synonym for erase head.
- error:
- (1) A discrepancy between a computed, observed, or measured value or condition and the true, specified, or theoretically correct value or condition. (2) Any invalid condition experienced by a system; for example, an attempt to divide by zero.
- error control:
- In data communications, that part of a protocol that enables error detection, and possibly error correction.
- error control character:
- Synonym for accuracy control character.
- error control software:
- Software that monitors a data processing system to detect, record, and possibly to correct errors.
- error correction:
- A method used to correct erroneous data produced during the transmission, transfer, or storage of data.
- error-correction learning:
- In artificial neural networks, supervised learning using the difference between the desired output value and the actual output value to modify the connection weights.
- error detection:
- A method of determining whether data have been transmitted or transferred incorrectly.
- error message:
- An indication that an error has been detected.
- error prediction:
- A quantitative statement about the expected number or nature of errors in a system or component.
- error range:
- (1) The set of values that an error may take. (2) Deprecated synonym for error span.
- error rate:
- The average number of errors per unit of time.
- error ratio:
- In communications, the ratio of the number of bits, characters, or blocks incorrectly received to the total number of bits, characters, or blocks sent during a specified time interval.
- error recovery:
- The process of correcting or bypassing the effects of an error to allow the functional unit to continue to perform a required function.
- error seeding:
- The process of intentionally adding known faults in a program for the purpose of monitoring the rate of detection and removal, and estimating the number of unknown faults remaining in the program. Synonymous with bug seeding, fault seeding.
- error span:
- The difference between the highest and the lowest error values.
- ESC:
- The escape character.
- escape character (ESC):
- The code-extension character used, in some cases with one or more succeeding characters, to indicate by some convention or agreement that the coded representations following the character or the group of characters are to be interpreted according to a different code or according to a different character set.
- escapement:
- The movement of the printing position by one increment relative to the printing medium.
- ETB:
- The end-of-transmission-block character.
- Ethernet:
- A 10-megabit baseband local area network signaling scheme that allows multiple nodes to access the transmission medium at will without prior coordination and that handles contention by using carrier sense and detection transmission. Ethernet, standardized by the IEEE 802.3 series, uses carrier sense multiple access with collision detection (CSMA/CD).
- Euler number:
- In computer graphics, the number of blobs in a binary image minus the number of children.
- evaluation function:
- In artificial intelligence, a function that is used to compute a value, or worth, of proposed intermediate states of a problem space during the search for a solution.
- evaluation report:
- A system follow-up report that describes how the system objectives have been met, identifies the remaining problems and is intended to assist future development.
- event:
- (1) An action or occurance. (2) In information theory, the concept "event" is to be understood as used in the theory of probability. For instance, an event may be:
- the presence of a specific element in a given set of elements;
- the occurrence of a specific character or word in a given message or in a given position of a message;
- any one of the distinct results an experiment may yield.
- event-driven processing:
- The operating mode in which the processing sequence is controlled by events, such as mouse movement or data entry. Some events may have higher priority than others and these may interrupt their processing.
- example-based learning:
- Synonym for learning from examples.
- example space:
- The set of all possible examples and counterexamples of a concept to be learned.
- exception:
- A condition that may arise during execution of a program, that may cause a deviation from the normal execution sequence, and for which means exist to define, raise, recognize, ignore, or handle it. For example: "(ON ERROR) condition" in PL/1; overflow; range error.
- exception handler:
- A portion of a program executed in response to a specific kind of exception.
- EXCEPT operation:
- Deprecated synonym for exclusion.
- excess-three code:
- The binary-coded decimal notation in which a decimal digit n is represented by the binary numeral that equals the number (n+3).
- exchange sort:
- A sort in which succeeding pairs of items in a set are examined; if the items in a pair are out of sequence according to the specified criteria, the positions of the items are exchanged; for example, a bubble sort. This process is repeated until all items are sorted.
- exclusion:
- (1) A dyadic logic operation whose results is True if and only if the first operand is True and the second if False. Truth values are frequently represented by 1 and 0 as in Boolean operations. (Figure 4 - Table of Boolean operations).
(2) A logic operator having the property that if P is a statement and Q is a statement, then P exclusion Q is true if P is true and Q is false, false if P is false, and false if both statements are true. P exclusion Q is often represented by a combination of AND and NOT symbols, such as P^~Q. Synonymous with NOT-IF-THEN operation.
- exclusion gate:
- A gate that performs the Boolean operation of exclusion (i.e., the complement of implication). Synonymous with nonimplication gate.
- exclusive-or gate:
- A gate that performs the Boolean operation of nonequivalence. For Boolean variables assuming values of 0 or 1, an exclusive-or gate outputs a value 1 if and only if exactly one of its two input values is 1; otherwise it outputs a value 0. Synonymous with XOR gate.
- executable:
- Pertaining to the task state in which a task exists after elaboration and before it is completed. An executable task is either ready, running, or blocked. The term used in Ada is "callable". (Figure 58 - State transition diagram).
- executable documentation:
- A hypermedia node that contains an executable program or contains a hyperlink to an executable program that is used to perform an action.
- execute:
- To carry out one or more instructions of a program by a computer.
- execution:
- The process of performing one or more instructions of a program by a computer.
- execution duration:
- The amount of time needed for the execution of a particular program. Execution duration is an elapsed time and is generally different from processor time. Synonymous with run duration, running time.
- execution monitor:
- A software tool or hardware device that operates concurrently with a system or functional unit and supervises, records, analyzes, or verifies the operation of the system or functional unit.
- execution profile:
- A representation of the absolute or relative execution frequencies or execution durations of the instructions or of the statements of a program.
- execution sequence:
- The order of the elaboration of declarations and of the execution of statements and parts of statements.
- execution time:
- Any instant at which the execution of a particular program takes place. Synonymous with run time.
- execution trace:
- A record of the sequence of instructions executed during the execution of a program. Synonymous with code trace, control-flow trace.
- executive:
- That portion of an operating system that includes the kernel and has hardware access privileges not directly available to user programs.
- executive program:
- Synonym for supervisory program.
- exhaustive attack:
- A trial-and-error attempt to violate computer_security by trying possible values of passwords or keys. Synonymous with brute-force attack. Contrast with analytical attack.
- exit:
- In programming, to execute an instruction or a statement in a program or part thereof that terminates the execution of that program or part.
- exit point:
- A point in a program, module, or statement at which execution of this program, module, or statement can terminate.
- exit statement:
- A simple statement used to end the execution of an enclosing language construct.
- exoskeleton:
- In virtual reality, a mechanically linked structure for the control of and feedback from an application.
- expand:
- (1) To return compressed data to their original form. (2) To enlarge the size of a window.
- expansion:
- Synonym for dilation.
- expansion board:
- A board that a user can install in an expansion slot to add memory or special features to a computer. Synonymous with add-on board.
- expansion card:
- An expansion device, in size similar to a credit card, such as per
PCMCIA specifications.
- expansion slot:
- A connector in a computer into which a user can plug an expansion board. The connector supplies power to the expansion board and connects it to the data bus, address bus and control signals of the motherboard.
- expansion unit:
- Synonym for docking station.
- expedited data unit:
- In OSI, a short service data unit whose delivery to a peer entity in the destination open system is ensured before the delivery of any subsequent service data units sent on that connection.
- expert system:
- A data processing system that provides for expertly solving problems in a given field or application area by drawing inferences with the aid of a knowledge base developed from human expertise. The term knowledge-based system is sometimes used synonymously with the term expert system, but the latter term emphasizes the knowledge of one or more experts. Some expert systems are able to improve their knowledge base and develop new inference rules based on their experience with previous problems.
- expert system shell:
- An empty expert system structure within which an application in a particular field of expertise is developed. An expert system shell typically consists of a high-level language for knowledge representation, one or more inference engines and interface programs.
- expiration date indication service:
- A service that allows the originator to indicate to the recipient the date and time after which the interpersonal message will be invalid.
- explanation-based learning:
- Synonym for analytic learning.
- explanation facility:
- The component of an expert system that explains how solutions were derived and justifies the steps used in reaching them.
- exploitable channel:
- In computer security, a channel that is usable or detectable by subjects external to the trusted computing base.
- explosion proof:
- Pertaining to equipment that will neither explode nor cause explosion.
- exponent:
- In floating-point representation, the numeral that denotes the power to which the floating-point base is raised before being multiplied by the coefficient to determine the real number represented. Example: One floating-point representation of the number 0.0001234 is
0.1234E-3
where
0.1234 is the coefficient;
-3 is the exponent, designated by E.
The numerals are expressed in the variable-point decimal system; the floating-point base is 10.
- export:
- In electronic mail, a transmittal step in which a message transfer agent conveys an information object to an access unit in order to convey it to an external communication system.
- export/import:
- (1) The transfer and conversion of data from one program to another. (2) In an information resource dictionary system, pertaining to the set of commands, controls, and other procedural elements necessary to move the contents of one information resource dictionary to another.
- exposure:
- In computer security, the potential compromise associated with an attack exploiting a corresponding vulnerability. (Figure 57 - Levels of security risks).
- expression:
- A language construct that defines the computation of a data value as a result from one or more operands. Operands may be literals, identifiers, function calls.
- EXT:
- The end-of-text character.
- extended binary-coded decimal interchange code (EBCDIC):
- A standard code that consists of 8-bit coded characters and now largely replaced by ASCII.
- extended time scale:
- The time scale used in data processing when the time scale factor is greater than one.
- extensibility:
- The capability of a programming language to allow the specification of new language constructs and their use in the same syntactic manner as the standard language constructs.
- extensible language:
- A programming language that can be altered or can alter itself to provide a programmer with additional user-specified capabilities; for example Ada, C++, Java, LISP, LOGO, Prolog, and Smalltalk.
- external:
- In programming, pertaining to a language construct that is defined outside the module in which it is referenced. A declaration may be required within the module to provide a name and to indicate that the complete definition is external.
- external coupling:
- Coupling in which the coupling of variables can be controlled by limiting it to those variables that are formally declared to be external. PL/I is one of the programming languages with this capability.
- external delay:
- Time lost due to circumstances beyond the control of the operator or maintenance engineer; for example, failure of an external power source.
- external level:
- A level of consideration at which all aspects deal with the user-oriented representation of information visible at the input and at the output of an information system.
- external modem:
- A modem that resides outside of the computer with which it interfaces. Contrast with internal modem.
- external program parameter:
- In a program, a parameter that must be bound during the calling of the program.
- external schema:
- The part of a database schema that pertains to the external level and that defines a particular user view.
- external sort:
- A sort that requires the use of external storage because the set of items to be sorted cannot be held in the available internal storage at one time.
- external storage:
- A storage device that is accessible to a processor only through input/output channels. Synonymous with auxiliary storage.
- extract:
- To select and remove from a group of items those which meet specific criteria.
- extranet:
- An IP network that includes access to or from selected external organizations, such as customers or suppliers, but not to the general public. The connection may be by leased lines, dial-up, or network interconnections. The overall network may be, but is not necessarily a virtual private network.
- extra pulse:
- An inadmissible additional pulse that occurs during recording or reading.
- extra sector:
- A sector that is written on a floppy disk track in excess of the standard number of sectors, as part of a method of copy protection.
- extra track:
- A track that is written on a floppy disk in excess of the standard number of tracks, as part of a method of copy protection.
- extrusion:
- In computer graphics, a sweep representation created by moving a two-dimensional area along a path normal to the plane of the area to create a volume. The representation of objects is done in a manner similar to extruding metal or plastic through a die with the desired cross-section. Simple extrusions involve scaling the cross section as it is swept to produce a tapered object or sweeping the cross-section along a linear path that is not normal to it. Synonymous with translational sweep.
- eye-movement detector:
- A device that traces eye movements; for example, in the form of a pair of spectacles and tiny infrared light-emitting diodes.
- eye tracker:
- A functional unit capable of following the movements of the human eye for interfacing with a computer. Synonymous with eye tracking unit.
- eye tracking unit:
- Synonym for eye tracker.
- e-zine:
- Periodical publication that is stored on a file server and that may be distributed or accessed via a computer network. Synonymous with electronic magazine, zine.