Delaunay triangulation

<mathematics, graphics>

(After B. Delaunay) For a set S of points in the Euclidean plane, the unique triangulation DT(S) of S such that no point in S is inside the circumcircle of any triangle in DT(S). DT(S) is the dual of the voronoi diagram of S.

delayed control-transfer


A technique used on the SPARC processor to reduce the effect of pipeline breaks by executing the instruction after a branch instruction (the "delay instruction" in the "delay slot"). If there is no useful instruction which can be placed in the delay slot then the "annul bit" on the control transfer instruction can be set, preventing execution of the delay instruction (unless the control transfer is conditional and is taken).

Annulled branches are indicated in SPARC assembler language by appending ",A" to the operation code. For example,

 LOOP: ...
 CMP    %L0,10
 ADD     %L2, %L3, #L4

If the delay instruction is also a control transfer instruction then it gets more complicated. Both control transfer instructions are executed (but not the following instruction) and, assuming they are both taken, control is transferred briefly to the destination of the first and then immediately to the destination of the second.

Last updated: 2001-06-26

delay instruction

delayed control-transfer

delay slot

delayed control-transfer


<operating system>

1. (Or "erase") To make a file inaccessible.

Usually this operation only deletes information from the tables the file system uses to locate named files; the file's contents still exist on disk and can sometimes be recovered by scanning the whole disk for strings which are known to have been in the file. Files created subsequently on the same disk are quite likely to reuse the same blocks and thus overwrite the deleted file's data permanently.


2. The control character with ASCII code 127. Usually entering this character from the keyboard deletes the last character typed from the input buffer. Sadly there is great confusion between operating systems and keyboard manufacturers as to whether this function should be assigned to the delete or backspace key/character.

The choice of code 127 (binary 1111111) is not arbitrary but dates back to the use of paper tape for input. The delete key rewound the tape by one character and punched out all seven holes, thus obliterating whatever character was there before. The tape reading software ignored any delete characters in the input.

Last updated: 1996-12-01



A character or string used to separate, or mark the start and end of, items of data in, e.g., a database, source code, or text file.

See also: record.

Last updated: 2001-03-16


/dee-lint/ To modify code to remove problems detected when linting. Confusingly, this process is also referred to as "linting" code.

[Jargon File]


An embedding coordinate language for parallel programming, implemented on Sequent Symmetry, Cray, BBN Butterfly.

["Parallel Programming with Coordination Structures", S. Lucco et al, 18th POPL, pp.197-208 (1991)].

Delivered Source Instruction

<programming, unit>

(DSI) One line of source code (LOC) developed by a project.

DSI is the primary input to many tools for estimating software cost. The term "delivered" is generally meant to exclude non-delivered support software such as test drivers. However, if these are developed with the same care as delivered software, with their own reviews, test plans, documentation, etc., then they should be counted. The "source instructions" include all program instructions created by project personnel and processed into machine code by some combination of preprocessors, compilers, and assemblers. It excludes comments and unmodified utility software. It includes job control language, format statements, and data declarations.

Last updated: 1996-05-29

Dell Computer Corporation


One of the biggest US manufacturers of IBM PC compatibles.

"From notebooks to networks", their slogan says.

Last updated: 1996-05-29


<company, communications>

1. A US Internet service provider.


Last updated: 1995-04-06


2. Borland's Object Oriented Pascal (OOPascal) Rapid Application Development package for Microsoft Windows. Delphi combines visual, component-based design with an optimising native code compiler and scalable database access.

Last updated: 1996-05-27

Delphi Technique

<programming, tool>

A group forecasting technique, generally used for future events such as technological developments, that uses estimates from experts and feedback summaries of these estimates for additional estimates by these experts until reasonable consensus occurs. It has been used in various software cost-estimating activities, including estimation of factors influencing software costs.

Last updated: 1996-05-29



1. An expression-based language developed by J.C. Cleaveland in 1978.

2. A string-processing language with single-character commands from Tandem Computers.

3. A language for system specification of simulation execution.

["System Description and the DELTA Language", E. Holback-Hansen et al, DELTA Proj Rep 4, Norweg Comput Ctr, Feb 1977].

4. A COBOL generating language produced by Delta Software Entwicklung GmbH.

Last updated: 2000-08-02


1. A quantitative change, especially a small or incremental one (this use is general in physics and engineering). "I just doubled the speed of my program!" "What was the delta on program size?" "About 30 percent." (He doubled the speed of his program, but increased its size by only 30 percent.)

2. [Unix] A diff, especially a diff stored under the set of version-control tools called SCCS (Source Code Control System) or RCS (Revision Control System). See change management.

3. A small quantity, but not as small as epsilon. The jargon usage of delta and epsilon stems from the traditional use of these letters in mathematics for very small numerical quantities, particularly in "epsilon-delta" proofs in limit theory (as in the differential calculus). The term delta is often used, once epsilon has been mentioned, to mean a quantity that is slightly bigger than epsilon but still very small. "The cost isn't epsilon, but it's delta" means that the cost isn't totally negligible, but it is nevertheless very small. Common constructions include "within delta of ---", "within epsilon of ---": that is, "close to" and "even closer to".

[Jargon File]

Last updated: 2000-08-02


Definition and Design of an open Dependable Distributed system architecture. An Esprit project investigating the achievement of dependability in open distributed systems, including real-time systems.

delta conversion

delta reduction


A Prolog extension with AND-parallelism, don't-know nondeterminism and interprocess communication using synchronous event goals and distributed backtracking.

["Delta-Prolog: A Distributed Logic Programming Language", L.M. Pereira et al, Intl Conf 5th Gen Comp Sys, Nov 1984].

delta reduction


In lambda-calculus extended with constants, delta reduction replaces a function applied to the required number of arguments (a redex) by a result. E.g. plus 2 3 --> 5. In contrast with beta reduction (the only kind of reduction in the pure lambda-calculus) the result is not formed simply by textual substitution of arguments into the body of a function. Instead, a delta redex is matched against the left hand side of all delta rules and is replaced by the right hand side of the (first) matching rule. There is notionally one delta rule for each possible combination of function and arguments. Where this implies an infinite number of rules, the result is usually defined by reference to some external system such as mathematical addition or the hardware operations of some computer. For other types, all rules can be given explicitly, for example Boolean negation:

 not True  = False
 not False = True

Last updated: 1997-02-20


A distributed processing environment concerned with fault-tolerant and process-control applications from the Esprit Delta-4 project.

Nearby terms:

DEKDelaunay triangulationdelayed control-transferdelay instruction

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