<communications> A bit signaling procedure used in most T1 transmission facilities where one bit from every sixth frame of each of 24 T1 subchannels is used for carrying supervisory signaling.
[What does it stand for? Is this the same as "bit robbing"?]
(1997-05-05)
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<jargon> /*-breev'/, /*-brev'/ Common abbreviation for "abbreviation".
(1995-02-27)
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<language> (ATLAS) A Mil-spec language for automatic testing of avionics equipment. ATLAS replaced Gaelic and several other test languages.
["IEEE Standard ATLAS Test Language", IEEE Std 416-1976].
(2000-04-03)
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1. <computer> Atanasoff-Berry Computer.
2. <language> An imperative language and programming environment from CWI, Netherlands. It is interactive, structured, high-level, and easy to learn and use. It is a general-purpose language which you might use instead of BASIC, Pascal or AWK. It is not a systems-programming language but is good for teaching or prototyping.
ABC has only five data types that can easily be combined; strong typing, yet without declarations; data limited only by memory; refinements to support top-down programming; nesting by indentation. Programs are typically around a quarter the size of the equivalent Pascal or C program, and more readable.
ABC includes a programming environment with syntax-directed editing, suggestions, persistent variables and multiple workspaces and infinite precision arithmetic.
An example function words to collect the set of all words in a document:
HOW TO RETURN words document:
PUT {} IN collection
FOR line in document:
FOR word IN split line:
IF word not.in collection:
INSERT word IN collection
RETURN collection
Interpreter/compiler, version 1.04.01, by Leo Geurts,
Lambert Meertens, Steven Pemberton <Steven.Pemberton@cwi.nl>.
ABC has been ported to Unix, MS-DOS, Atari, Macintosh.
http://cwi.nl/cwi/projects/abc.html.
FTP eu.net, FTP nluug.nl, FTP uunet.
Mailing list: <abc-list-request@cwi.nl>.
E-mail: <abc@cwi.nl>.
["The ABC Programmer's Handbook" by Leo Geurts, Lambert Meertens and Steven Pemberton, published by Prentice-Hall (ISBN 0-13-000027-2)].
["An Alternative Simple Language and Environment for PCs" by Steven Pemberton, IEEE Software, Vol. 4, No. 1, January 1987, pp. 56-64.]
(1995-02-09)
2. <language> Argument, Basic value, C?.
An abstract machine for implementation of functional languages and its intermediate code.
[P. Koopman, "Functional Programs as Executable Specifications", 1990].
(1995-02-09)
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<language> An extension of ALGOL 60 with arbitrary data structures and user-defined operators, for symbolic mathematics.
["ABC ALGOL, A Portable Language for Formula Manipulation Systems", R.P. van de Riet, Amsterdam Math Centrum 1973].
(1994-10-28)
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<language> An Object-Based Concurrent Language.
The language for the ABCL MIMD system, written by Akinori Yonezawa <matsu@is.s.u-tokyo.ac.jp> of Department of Information Science, Tokyo University in 1986. ABCL/1 uses asynchronous message passing to objects. It requires Common Lisp. Implementations in KCL and Symbolics Lisp are available from the author.
ftp://camille.is.s.u-tokyo.ac.jp/.
E-mail: <abcl@is.s.u-tokyo.ac.jp>.
["ABCL: An Object-Oriented Concurrent System", A. Yonezawa ed, MIT Press 1990]. (1990-05-23).
(1995-02-09)
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<language> A concurrent object-oriented language, an extension of ABCL/1 based on C.
["An Implementation of An Operating System Kernel using Concurrent Object Oriented Language ABCL/c+", N. Doi et al in ECOOP '88, S. Gjessing et al eds, LNCS 322, Springer 1988].
(1994-11-08)
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<language> A reflective subset of ABCL/1, written in ABCL/1 by Yonezawa of Tokyo Institute of Technology in 1988.
ftp://camille.is.s.u-tokyo.ac.jp/pub/abclr.
["Reflection in an Object-Oriented Concurrent Language", T. Watanabe et al, SIGPLAN Notices 23(11):306-315 (Nov 1988)].
(1994-11-08)
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<language> An object-oriented, concurrent, reflective language based on Hybrid Group Architecture. ABCL/R2 was produced by <masuhara@is.s.u-tokyo.ac.jp>, <matsu@is.s.u-tokyo.ac.jp>, <takuo@is.s.u-tokyo.ac.jp>, <yonezawa@is.s.u-tokyo.ac.jp>, at the Tokyo Institute of Technology in 1992.
As a reflective language, an ABCL/R2 program can dynamically control its own behaviour, such as scheduling policy, from within a user-program. This system has almost all functions of ABCL/1 and is written in Common Lisp.
ftp://camille.is.s.u-tokyo.ac.jp/pub/abclr2/.
(1993-01-28)
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<logic> The process of inference to the best explanation.
"Abduction" is sometimes used to mean just the generation of hypotheses to explain observations or conclusionsm, but the former definition is more common both in philosophy and computing.
The semantics and the implementation of abduction cannot be reduced to those for deduction, as explanation cannot be reduced to implication.
Applications include fault diagnosis, plan formation and default reasoning.
Negation as failure in logic programming can both be given an abductive interpretation and also can be used to implement abduction. The abductive semantics of negation as failure leads naturally to an argumentation-theoretic interpretation of default reasoning in general.
[Better explanation? Example?]
["Abductive Inference", John R. Josephson <jj@cis.ohio-state.edu>].
(2000-12-07)
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<jargon> /o'bend/, /*-bend'/ ABnormal END. Abnormal termination (of software); crash; lossage. Derives from an error message on the IBM 360; used jokingly by hackers but seriously mainly by code grinders. Usually capitalised, but may appear as "abend". Hackers will try to persuade you that ABEND is called "abend" because it is what system operators do to the computer late on Friday when they want to call it a day, and hence is from the German "Abend" = "Evening".
(1994-11-08)
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<games> The first popular open source MUD. The first version of AberMUD, named after Aberystwyth, UK, was written in B by Alan Cox, Richard Acott, Jim Finnis, and Leon Thrane, at University of Wales, Aberystwyth for an old Honeywell mainframe and opened in 1987. The gameplay was heavily influenced by MUD1, written by Roy Trubshaw and Richard Bartle, which Alan Cox had played at the University of Essex. In late 1988, Alan Cox ported AberMUD to C so it could run under UNIX on Southampton University's Maths machines. This version was named AberMUD2. Various other versions followed.
(2008-11-24)
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<language> A simple language for accountants.
["ABLE, The Accounting Language, Programming and Reference Manual," Evansville Data Proc Center, Evansville, IN, Mar 1975].
[Listed in SIGPLAN Notices 13(11):56 (Nov 1978)].
(1994-11-08)
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<programming> To terminate a program or process abnormally and usually suddenly, with or without diagnostic information. "My program aborted", "I aborted the transmission". The noun form in computing is "abort", not "abortion", e.g. "We've had three aborts over the last two days".
If a Unix kernel aborts it is known as a panic.
(1997-01-07)
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1. <networking> Alternating bit protocol.
2. Microsoft Address Book Provider.
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<mathematics> The horizontal or x coordinate on an (x, y) graph; the input of a function against which the output is plotted.
The vertical or y coordinate is the "ordinate".
(1997-07-08)
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<language> An early declarative language from the University of Aberdeen.
["ABSET: A Programming Language Based on Sets", E.W. Elcock et al, Mach Intell 4, Edinburgh U Press, 1969, pp.467-492].
(1994-11-08)
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<file system> A path relative to the root directory. Its first character must be the pathname separator.
(1996-11-21)
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<file system> A pathname relative to the root directory.
(1996-11-21)
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<philosophy> A description of a concept that leaves out some information or details in order to simplify it in some useful way.
Abstraction is a powerful technique that is applied in many areas of computing and elsewhere. For example: abstract class, data abstraction, abstract interpretation, abstract syntax, Hardware Abstraction Layer.
(2009-12-09)
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<programming> In object-oriented programming, a class designed only as a parent from which sub-classes may be derived, but which is not itself suitable for instantiation. Often used to "abstract out" incomplete sets of features which may then be shared by a group of sibling sub-classes which add different variations of the missing pieces.
(1994-11-08)
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<programming> (ADT) A kind of data abstraction where a type's internal form is hidden behind a set of access functions. Values of the type are created and inspected only by calls to the access functions. This allows the implementation of the type to be changed without requiring any changes outside the module in which it is defined.
Objects and ADTs are both forms of data abstraction, but objects are not ADTs. Objects use procedural abstraction (methods), not type abstraction.
A classic example of an ADT is a stack data type for which functions might be provided to create an empty stack, to push values onto a stack and to pop values from a stack.
(2003-07-03)
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<theory> A partial execution of a program which gains information about its semantics (e.g. control structure, flow of information) without performing all the calculations. Abstract interpretation is typically used by compilers to analyse programs in order to decide whether certain optimisations or transformations are applicable.
The objects manipulated by the program (typically values and functions) are represented by points in some domain. Each abstract domain point represents some set of real ("concrete") values.
For example, we may take the abstract points "+", "0" and "-" to represent positive, zero and negative numbers and then define an abstract version of the multiplication operator, *#, which operates on abstract values:
*# | + 0 - ---|------ + | + 0 - 0 | 0 0 0 - | - 0 +An interpretation is "safe" if the result of the abstract operation is a safe approximation to the abstraction of the concrete result. The meaning of "a safe approximation" depends on how we are using the results of the analysis.
If, in our example, we assume that smaller values are safer then the "safety condition" for our interpretation (#) is
a# *# b# <= (a * b)#where a# is the abstract version of a etc.
In general an interpretation is characterised by the domains used to represent the basic types and the abstract values it assigns to constants (where the constants of a language include primitive functions such as *). The interpretation of constructed types (such as user defined functions, sum types and product types) and expressions can be derived systematically from these basic domains and values.
A common use of abstract interpretation is strictness analysis.
See also standard interpretation.
(1994-11-08)
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1. Generalisation; ignoring or hiding details to capture some kind of commonality between different instances. Examples are abstract data types (the representation details are hidden), abstract syntax (the details of the concrete syntax are ignored), abstract interpretation (details are ignored to analyse specific properties).
2. <programming> Parameterisation, making something a function of something else. Examples are lambda abstractions (making a term into a function of some variable), higher-order functions (parameters are functions), bracket abstraction (making a term into a function of a variable).
Opposite of concretisation.
(1998-06-04)
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1. <language> A processor design which is not intended to be implemented as hardware, but which is the notional executor of a particular intermediate language (abstract machine language) used in a compiler or interpreter. An abstract machine has an instruction set, a register set and a model of memory. It may provide instructions which are closer to the language being compiled than any physical computer or it may be used to make the language implementation easier to port to other platforms.
A virtual machine is an abstract machine for which an interpreter exists.
Examples: ABC, Abstract Machine Notation, ALF, CAML, F-code, FP/M, Hermes, LOWL, Christmas, SDL, S-K reduction machine, SECD, Tbl, Tcode, TL0, WAM.
2. <theory> A procedure for executing a set of instructions in some formal language, possibly also taking in input data and producing output. Such abstract machines are not intended to be constructed as hardware but are used in thought experiments about computability.
Examples: Finite State Machine, Turing Machine.
(1995-03-13)
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<language> (AMN) A language for specifying abstract machines in the B-Method, based on the mathematical theory of Generalised Substitutions.
(1995-03-13)
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<language, data> A form of representation of data that is independent of machine-oriented structures and encodings and also of the physical representation of the data. Abstract syntax is used to give a high-level description of programs being compiled or messages passing over a communications link.
A compiler's internal representation of a program will typically be an abstract syntax tree. The abstract syntax specifies the tree's structure is specified in terms of categories such as "statement", "expression" and "identifier". This is independent of the source syntax (concrete syntax) of the language being compiled (though it will often be very similar).
A parse tree is similar to an abstract syntax tree but it will typically also contain features such as parentheses which are syntactically significant but which are implicit in the structure of the abstract syntax tree.
(1998-05-26)
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<language, standard, protocol> (ASN.1, X.208, X.680) An ISO/ITU-T standard for transmitting structured data on networks, originally defined in 1984 as part of CCITT X.409 '84. ASN.1 moved to its own standard, X.208, in 1988 due to wide applicability. The substantially revised 1995 version is covered by the X.680 series.
ASN.1 defines the abstract syntax of information but does not restrict the way the information is encoded. Various ASN.1 encoding rules provide the transfer syntax (a concrete representation) of the data values whose abstract syntax is described in ASN.1. The standard ASN.1 encoding rules include BER (Basic Encoding Rules - X.209), CER (Canonical Encoding Rules), DER (Distinguished Encoding Rules) and PER (Packed Encoding Rules).
ASN.1 together with specific ASN.1 encoding rules facilitates the exchange of structured data especially between application programs over networks by describing data structures in a way that is independent of machine architecture and implementation language.
OSI Application layer protocols such as X.400 MHS electronic mail, X.500 directory services and SNMP use ASN.1 to describe the PDUs they exchange.
Documents describing the ASN.1 notations: ITU-T Rec. X.680, ISO 8824-1; ITU-T Rec. X.681, ISO 8824-2; ITU-T Rec. X.682, ISO 8824-3; ITU-T Rec. X.683, ISO 8824-4
Documents describing the ASN.1 encoding rules: ITU-T Rec. X.690, ISO 8825-1; ITU-T Rec. X.691, ISO 8825-2.
[M. Sample et al, "Implementing Efficient Encoders and Decoders for Network Data Representations", IEEE Infocom 93 Proc, v.3, pp. 1143-1153, Mar 1993. Available from Logica, UK].
See also snacc.
(2005-07-03)
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<compiler> (AST) A data structure representing something which has been parsed, often used as a compiler or interpreter's internal representation of a program while it is being optimised and from which code generation is performed. The range of all possible such structures is described by the abstract syntax.
(1994-11-08)
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<language> (ASDL) A language developed as part of Esprit project GRASPIN, as a basis for generating language-based editors and environments. It combines an object-oriented type system, syntax-directed translation schemes and a target-language interface.
["ASDL - An Object-Oriented Specification Language for Syntax-Directed Environments", M.L. Christ-Neumann et al, European Software Eng Conf, Strasbourg, Sept 1987, pp.77-85].
(1996-02-19)
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<graphics> (AWT) Java's platform-independent windowing, graphics, and user-interface toolkit. The AWT is part of the Java Foundation Classes (JFC) - the standard API for providing a graphical user interface (GUI) for a Java program.
Compare: SWING.
["Java in a Nutshell", O'Reilly].
http://java.sun.com/products/jdk/awt/.
(2000-07-26)
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<language> An early declarative language from the University of Aberdeen which anticipated a number of features of Prolog.
["ABSYS: An Incremental Compiler for Assertions", J.M. Foster et al, Mach Intell 4, Edinburgh U Press, 1969, pp. 423-429].
(1994-11-08)
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