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RAD:

rapid application development.

radial basis function (RBF):

In artificial neural networks, an activation function which is centered at a point specified by the connection weight vector and whose position and width are adjusted by learning. A radial basis function has a maximum or a minimum, in contrast with the usual activation functions that are monotonic. The most used radial basis function is the Gaussian function.

radial basis function network:

In artificial neural networks, a feedforward network in which each hidden neuron uses a radial basis function as the activation function and the output neurons implement linear combinations of these radial basis functions. Synonymous with RBF network.

radio button:

An object in a graphical user interface presenting choice by clicking on one of such objects.

radix:

In radix notation, the positive integer greater than one by which the weight of a given digit place is multiplied to obtain the weight of the digit place with the next higher weight; for example: in the decimal system, the radix of each digit place is 10 and the weight at each digit place is an integral power of ten. The term "base" is deprecated in this sense because of its mathematical use.

radix complement:

In fixed-radix notation, a complement that can be derived from a given number by subtracting it from a specified power of the radix; for example: in the decimal system using three digits, 830 is the radix complement of 170, the power of the radix being 1000 (=10³). The radix complement may be obtained by first deriving the diminished radix complement, then adding one to the least significant digit of the result and executing any carries required.

radix-minus-one complement:

Synonym for diminished radix complement.

radix notation:

A positional notation in which the ratio of the weight of any one digit place to the weight of the digit place with the next lower weight is a positive integer greater than one. The permissible values of the digit in any digit place range from zero to that integer minus one.

radix point:

In a representation of a number expressed in radix notation, the location of the separation of the digits associated with the integral part from those associated with the fractional part.

ragged left:

Pertaining to text that is not aligned to the left margin.

ragged right:

Pertaining to text that is not aligned to the right margin.

RAID:

A functional unit that includes multiple hard disk drives controlled by an array manager and that provides fault tolerance in the event of drive failure. RAID is the abbreviation for redundant array of independent disks, redundant array of inexpensive disks.

raise:

To cause an exception to be signaled based upon the occurrence of a specified condition.

raise an exception:

Synonym for raise.

raise statement:

A simple statement that propagates an exception or causes it to occur.

RAM:

Literally, any memory that can be addressed randomly. Note, however, in usage, the term RAM is typically used to mean read/write memory as distinct from ROM which is read-only memory. RAM is the abbreviation for random access memory.

random access:

Deprecated synonym for direct access.

random-access memory:

RAM.

randomly connected network:

An artificial neural network whose artificial neurons are connected at random. Synonymous with random network.

random network:

Synonym for randomly connected network.

random number:

(1) A number obtained by chance. (2) A number selected from a known set of numbers in such a way that each number in the set has the same probability of occurrence.

random number sequence:

A sequence of numbers, each of which cannot be predicted solely from a knowledge of its predecessors.

range:

In programming languages, a contiguous set of data values of a scalar type. Contrast with span.

range specification:

In text processing, specification by a user of a particular span of text that is to be edited. This span may be selected based on units such as word, line, paragraph, sentence, or page.

rank:

Synonym for level number.

rapid application development (RAD):

A system for quickly building application software.

rapid enrollment:

In speech recognition, enrollment where word models are built based upon the reading of a given text rather than on the training of each word in the system's vocabulary.

raster:

A predetermined pattern of lines that provides uniform coverage of a display space by scanning.

raster display:

A display image generated by a display device that uses a raster scan.

raster graphics:

Computer graphics in which a display image is composed of an array of pixels arranged in rows and columns.

rasterization:

A rendering technique that produces a pixel map for a display image.

raster plotter:

A plotter that generates a display image on a display surface using a line-by-line scanning technique.

raster scan:

A technique for generating or recording the elements of a display image by means of a line-by-line sweep across the entire display space.

raster unit:

The distance between adjacent pixels.

rate:

A quantity that expresses the pace at which time passes for a time base. Example: Consider a time base that operates in a time coordinate system that has a time base of 60 per second. If that time base has a rate 1, then 60 time units are processed by a second. If the rate is set to 1/2, then 30 time units pass per second. If the rate is 2, then 120 time units pass per second. A rate is multiplied by the time scale to obtain the number of time units that pass per second.

rational number:

A real number that is the quotient of an integer divided by an integer other than zero.

raw image:

An acquired image prior to any processing.

ray tracing:

A technique for determining the parts of the scene that should be displayed in the resulting display image at any given instance by tracing imaginary rays of light from the viewer's eye to the objects in a scene.

RBE:

remote batch entry.

RBF:

radial basis function.

RBF network:

Synonym for radial basis function network.

RDBMS:

relational database management system.

read:

To obtain data from an input device, from a storage device, or from a data medium.

read access:

An access right that gives permission to read data.

read cycle time:

The minimum time interval between the starts of successive read cycles of a storage device that has separate reading and writing cycles.

reader:

(1) A functional unit that is used for the acquisition or interpretation of data from a storage device, from a data medium, or from another source. (2) In micrographics, a device that enlarges microimages for viewing.

read head:

A magnetic head capable only of reading.

read-only memory (ROM):

A storage device in which data, under normal conditions, can only be read.

read path:

In a reader, the path that has a read station.

read station:

The location in a reader where data on a data medium are read.

read/write head:

A magnetic head capable of reading and writing.

read/write memory:

A storage device in which data can be written and read.

read/write opening:

Synonym for read/write slot.

read/write slot:

An opening in the jacket of a floppy disk to allow access to the tracks by the read/write heads. Synonymous with read/write opening.

ready:

Pertaining to the task state of an executable task in which the task is waiting for processing and is not blocked. (Figure 58 - State transition diagram).

real address:

The address of a storage location in the main storage part of a virtual memory.

reality engine:

Synonym for artificial-reality engine.

real literal:

A numeric literal used to represent a real number.

realm:

In a network model, a part of a database that can be opened and closed as a unit.

real memory:

The physical memory in a virtual memory.

real number:

A number that may be represented by a finite or infinite numeral in a fixed-radix notation.

real open system:

A real system that complies with the requirements of open systems interconnection standards in its communication with other real systems.

real storage:

Deprecated synonym for real memory.

real system:

In an OSI context, a set of one or more computers, associated software, peripheral equipment, terminals, human operators, physical processes, and means of communication that form an autonomous whole capable of performing data processing or data transfer or both.

real-time:

Pertaining to the processing of data by a computer in connection with another process outside the computer according to time requirements imposed by the outside process. "Real-time" is also used to describe systems operating in conversational mode and processes that can be influenced by human intervention while they are in progress.

real-time environment:

An operating environment that supports the execution of real-time programs.

real-time imaging:

The graphics or images synchronized with real-world time and events

real-time operation:

In analog computing, operation in the compute mode, during which the time scale factor is 1.

real-time simulation:

The operation of a simulator such that the time scale factor is equal to one for a physical time specified by the system being simulated, and by the corresponding computer time of the simulator.

real type:

A data type whose values represent real numbers, possibly by approximation; for example, the decimal number 0.1 in the binary system has an infinite number of digits, that is truncated in any actual binary representation. Real types are usually represented by fixed-point types or floating-point types.

reasoning:

The process by which a person or a computer system moves from some assumptions to a conclusion.

receipt:

In electronic mail, a transmittal step in which either a user agent conveys a message or report to its direct user, or another communication system conveys it to an indirect user.

receipt notification:

An interpersonal notification that reports to the originator of an interpersonal message the successful receipt of an interpersonal message. Successful receipt may include expected and arranged future receipt of the interpersonal message.

receiving service user:

In OSI, a service user that acts as a data sink during the data transfer phase of a connection or during a particular instance of connectionless-mode transmission.

recipient:

(1) The user to whom a message is addressed. If reception is intended but has not yet occurred, the term "intended recipient" should be used. Recipient lists may also include "potential recipients" not actually addressed. (2) The user or distribution list that may receive a message or to whom a message is addressed.

recognition time:

The time elapsed between the change of the values of a digital input signal and its recognition by a digital input unit.

recognition vocabulary:

The set of words and phrases that a speech recognizer identifies. Synonymous with passive vocabulary. Contrast with spoken vocabulary.

reconfigurable circuit:

An integrated logic circuit designed to perform any of several functions, as successively requested by the user.

reconfiguration:

In reliability, maintainability, and availability, the modification of the configuration of a functional unit in the presence of a fault or an error for the purpose of bringing that functional unit back to a state in which it can perform a required function.

record:

(1) A data object that is an instance of a record type. (2) In organization of data, a set of data elements treated as a unit. (3) To write data on a medium, such as magnetic tape, magnetic disk, or optical disk.

recording density:

Synonym for bit density.

recording layer:

A layer of an optical disk on, or in, which data is written during manufacture and/or use.

recording magnetic field:

In a magneto-optical disk, the magnetic field that switches between two opposite directions (perpendicular to the disk surface) according to the encoded information. When the focus spot of a laser beam heats the disk sufficiently, this magnetic field causes a permanent magnetic domain in the magneto-optical layer on the disk.

record layout:

The arrangement and structure of data or words in a record with a definition of the order and size of the component elements of the record.

record length:

The number of bytes, or any other appropriate unit, in a record. Synonymous with record size.

record separator character (RS):

The information separator used to identify a logical boundary between records.

record size:

Synonym for record length.

record type:

A composite type whose components are field types or other record types; for example: a personnel record may consist of personal data arranged as fields or subrecords within this personnel record. A record type defines a set of values and operations. An instance of such a record type may contain values which themselves are records.

recover:

To establish a previous or new status of all or part of a system, file, database, or other resource, or of the execution of a program so that required functions can be performed.

recovery:

(1) In data transmission, a process for resolving conflicting or erroneous conditions arising during the transfer of data. (2) The resetting of system resources to a point at which programs can be restored without error in functional processing. (3) In databases, the restoration of a database; for example, by means of backup files and after-images.

recovery and restart:

The procedures and capabilities available for reconstruction of the contents of a database to a state that prevailed before the detection of processing errors and before the occurrence of a hardware or software failure that resulted in the destruction of some or all of the stored data.

recovery time:

When sending or receiving pulses, the time required between the end of a pulse and the beginning of the next pulse. The term usually applies to the equipment that sends or receives pulses.

recurrent network:

An artificial neural network in which the connections between artificial neurons form at least one feedback loop; for example: Hopfield network, Boltzmann machine. A nonlayered network is a recurrent network. A layered network is recurrent if there are connections between neurons within a given layer or connections from a given neuron to a neuron in a layer back toward the input.

recursion:

A process in which a subprogram either contains a subprogram call on itself, or calls another subprogram that calls the original subprogram or that initiates a further chain of subprogram calls that eventually leads back to a subprogram call of the original subprogram.

recursively defined sequence:

A sequence of terms in which each term after the first is determined by an operation in which the operands include some or all of the preceding terms. In a recursively defined sequence, there may exist a finite number of nondefined terms.

redirection:

A transmittal event in which a message transfer agent replaces a user or distribution list among a message's immediate recipients with an alternate recipient.

reduced-instruction-set computer (RISC):

A computer characterized by a small set of instructions and a large collection of registers.

reduced instruction set computer processor:

Synonym for RISC processor.

redundancy:

(1) In a functional unit, the existence of a means for improving reliability in addition to the essential set of means for performing a required function. (2) In information theory, the amount R by which the decision content H₀ exceeds the entropy H; in mathematical notation: R = H₀ - H Example: Let {a,b,c} be a set of three events and let p(a) = 0.5, p(b) = 0.25, and p(c) = 0.25 be the probabilities of their occurrences. The redundancy of this set is: R = 1.58 Sh - 1.50 Sh = 0.08 Sh Usually, messages can be represented with fewer characters by using suitable codes; the redundancy may be considered as a measure of the decrease of the average length of the messages accomplished by appropriate coding. Redundancy is frequently used for error detection.

redundant array of inexpensive disks:

RAID.

redundant array of independent disks:

RAID.

redundant code:

A code according to which more characters, symbols, or signal elements than strictly necessary are used to represent data.

reel:

A cylinder with flanges on which tape may be wound.

reentrant:

Pertaining to a program or a part of a program in its executable version, that may be entered repeatedly, or may be entered before previous executions have been completed, and each execution of such a program is independent of all other executions.

reentry point:

A point in a program, module, or statement at which this program, module, or statement resumes execution following the execution of another program, module, or statement.

reference edge:

That edge of a data medium used to establish specifications or measurements in or on the data medium. Synonymous with guide edge.

referential integrity:

A property of a set of relations such that the attribute values of foreign keys are null values or are identical to the values of primary keys of other relations.

referral:

A suggestion to use an alternative access point, or directory system agent, given by a directory system agent to a directory user agent or another directory system agent, in case that a request to the directory system could not be resolved. The reason for a referral may be that the information affected by the request is logically too far away.

reflected binary code:

Synonym for gray code.

refresh:

The process of repeatedly producing a display image on a screen so that the image remains visible.

refresh rate:

The number of times per second at which a display image is refreshed.

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