A Simulation Process-Oriented Language

A# /A sharp/ A separable component of Version 2 of the {AXIOM*} computer algebra system. It provides a programming language with an {optimising compiler}, an {intermediate code} {interpreter}, and a library of data structures and mathematical {abstraction}s. The compiler produces {stand-alone executable} programs, {object} libraries in {native} {operating system} formats, {portable} {bytecode} libraries, {C} and {Lisp} {source code}. The A# programming language has support for {object-oriented} and {functional programming} styles. Both types and functions are {first class} values that can be manipulated with a range of flexible and composable {primitive}s and user programs. The A# language design places particular emphasis on compilation for efficient {machine code} and portability. Ports have been made to various 16, 32, and 64 bit architectures: {RS/6000}, {SPARC}, {DEC Alpha}, {i386}, {i286}, {Motorola 680x0}, {S 370}; several {operating system}s: {Linux}, {AIX}, {SunOS}, {HP/UX}, {Next}, {Mach} and other {Unix} systems, {OS/2}, {DOS}, {Microsoft Windows}, {VMS} and {CMS}; {C} compilers: {Xlc}, {gcc}, {Sun}, {Borland}, {Metaware} and {MIPS} C. (1995-02-07)

A Hardware Programming Language (AHPL) A {register}-level language by Hill and Peterson, some of whose operators resemble {APL}. HPSIM2 is a function-level simulator, available from Engrg Expt Sta, {University of Arizona}. ["Digital Systems: Hardware Organization and Design", F. Hill et al, Wiley 1987]. (1995-01-26)

A. K. Erlang (1878-1929) A Danish mathematician. {Erlang} the language and unit were named after him. Interested in the theory of probability, in 1908 Erlang joined the Copenhagen Telephone Company where he studied the problem of waiting times for telephone calls. He worked out how to calculate the fraction of callers who must wait due to all the lines of an exchange being in use. His formula for loss and waiting time was published in 1917. It is now known as the "Erlang formula" and is still in use today. {Biography (http://www-history.mcs.st-andrews.ac.uk/~history/Mathematicians/Erlang.html)}, {Biography (http://pass.maths.org.uk/issue2/erlang/index.html)}. [What was his name?] (2000-10-28)

A Language Encouraging Program Hierarchy (ALEPH) A language developed in about 1975. ["On the Design of ALEPH", D. Grune, CWI, Netherlands 1986]. (1997-02-27)

A Language for Attributed Definitions (ALADIN) A language for formal specification of {attributed grammar}s. ALADIN is the input language for the {GAG} compiler generator. It is {applicative} and {strongly typed}. ["GAG: A Practical Compiler Generator", Uwe Kastens et al, LNCS 141, Springer 1982]. (1995-04-14)

A Language with an Extensible Compiler (ALEC) A language Implemented using {RCC} on an {ICL 1906A}. ["ALEC - A User Extensible Scientific Programming Language", R.B.E. Napper et al, Computer J 19(1):25-31]. (1995-04-19)

A Manufacturing Language (AML) A {high-level language} developed by {IBM} in the 1980s for industrial {robots}. ["AML: A Manufacturing Language", R.H. Taylor et al, Inst J Robot Res 1(3):19-43]. (1995-09-25)

A PArse REquest Language (APAREL) A {PL/I} extension to provide {BNF} {parsing} routines, for {IBM 360}. ["APAREL: A Parse Request Language", R.W. Balzer et al, CACM 12(11) (Nov 1969)]. (1995-11-26)

A Programming Language (APL) A language designed originally by Ken Iverson at {Harvard University} in 1957-1960 as a notation for the concise expression of mathematical {algorithms}. It went unnamed (or just called {Iverson's Language}) and unimplemented for many years. Finally a subset, APL\360, was implemented in 1964. APL is an {interactive} {array-oriented} language with many innovative features. It was originally written using a non-standard {character set} but now can use {ISO8485}. It is {dynamically typed} with {dynamic scope}. APL introduced several functional forms but is not {purely functional}. {Dijkstra} got the size of it when he said that APL was a language designed to perfection - in the wrong direction. {IBM} once adopted APL - can one be ruder? Versions: APL\360, APL SV, VS APL, Sharp APL, Sharp APL/PC, APL*PLUS, APL*PLUS/PC, APL*PLUS/PC II, MCM APL, Honeyapple, and DEC APL. See also {Kamin's interpreters}. {APLWEB} translates {WEB} to {APL}. ["A Programming Language", Kenneth E. Iverson, Wiley, 1962]. ["APL: An Interactive Approach", 1976]. (2001-01-27)

A* search A {graph} search {algorithm}. A* is guaranteed to find a minimal solution path before any other solution paths, if a solution exists, in other words, it is an "{admissible}" search algorithm. Each path is assigned a value based on the cost of the path (e.g. its length) and an (under)estimate of the cost of completing the path, i.e. the cost of a path from the end of the current path to a solution. (1995-03-31)

A Simulation Process-Oriented Language (ASPOL) An {ALGOL}-like language for computer {simulation}. ["Process and Event Control in ASPOL", M.H. MacDougall, Proc Symp on Simulation of Computer Systems, NBS (Aug 1975)]. (1996-03-25)

A Tools Integration Standard (ATIS) An {object-oriented} interface to a set of services that allows the saving, accessing and managing of information in a common repository. Developed by {Atherton Technology} and {DEC}, based on an extended version of the {Software BackPlane}, proposed as an industry standard. (1994-10-25)

A-0 (Or A0) A language for the {UNIVAC I} or II, using {three-address code} instructions for solving mathematical problems. A-0 was the first language for which a {compiler} was developed. It was produced by {Grace Hopper}'s team at {Remington Rand} in 1952. Later internal versions were A-1, A-2, A-3, AT-3. AT-3 was released as {MATH-MATIC}. ["The A-2 Compiler System", Rem Rand, 1955]. [Sammet 1969, p. 12]. (1995-12-03)

a1 Address 1 code. An a1 code {interpreter}, by Matthew Newhook was used to test compiler output. It requires {gcc} 2.4.2 or higher and is portable to computers with {memory segment} protection. {(ftp://ftp.cs.mun.ca/pub/a1)} (1994-07-19)

A1 security {Orange Book}

A20 handler {IBM PC} memory manager software providing {HMA}. {XMM}s usually provide this functionality. Named after the 21st address line (A20), controlling the access to HMA. (1996-01-10)

A-3 {ARITH-MATIC}

A3D (Aureal 3-Dimensional?) A technology developed by {Aureal} that delivers sound with a three-dimensional effect through two speakers. Many modern {sound cards} and PC games now support this feature. A3D differs from the various forms of {surround sound} in that it only requires two speakers, while surround sound typically requires four or five. It is sometimes less convincing than surround sound but is supposedly better in {interactive} environments. For example, PC games in which sounds often move from one speaker to another favour A3D, while pre-recorded video favours surround sound. {Home (http://www.a3d.com/)}. (1999-01-26)

a56 An {assembler} for the {Motorola} {DSP56000} and {DSP56001} {digital signal processor}s by Quinn Jensen . Version 1.1 is available from an {alt.sources} archive or {(ftp://wuarchive.wustl.edu/)}. (1992-08-10)

AADL {Axiomatic Architecture Description Language}

AAL {ATM Adaptation Layer}

AAP {Association of American Publishers}

AAP DTD A {DTD} for a standard {SGML} document type for scientific documents, defined by the {Association of American Publishers}. (1994-11-08)

aard (Dutch for "earth") A tool to check memory use for {C++} programs, written by Steve Reiss (who names his programs after living systems). Aard tracks the state of each byte of memory in the {heap} and the {stack}. The state can be one of Undefined, Uninitialised, Free or Set. The program can detect invalid transitions (i.e. attempting to set or use undefined or free storage or attempting to access uninitialised storage). In addition, the program keeps track of heap use through {malloc} and {free} and at the end of the run reports memory blocks that were not freed and that are not accessible (i.e. {memory leaks}). The tools works using a spliced-in {shared library} on {SPARCs} running {C++} 3.0.1 under {SunOS} 4.X. {(ftp://wilma.cs.brown.edu/pub/aard.tar.Z)}. (1998-03-03)

AARP {Apple Address Resolution Protocol}

AARP probe packets {AARP} {packets} sent out on a nonextended {AppleTalk} network to discover whether a randomly selected node ID is being used by any node. If not, the sending node uses the node ID. If so, it chooses a different ID and sends more AARP probe packets. (1997-05-03)

AAUI {Apple Attachment Unit Interface}

A&B 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)

abbrev /*-breev'/, /*-brev'/ Common abbreviation for "abbreviation". (1995-02-27)

Abbreviated Test Language for Avionics Systems (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)

ABC 1. 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, {suggestion}s, {persistent variable}s 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 . ABC has been ported to {Unix}, {MS-DOS}, {Atari}, {Macintosh}. {Home (http://www.cwi.nl/cwi/projects/abc.html)} {FTP eu.net (ftp://ftp.eu.net/programming/languages/abc)}, {FTP nluug.nl (ftp://ftp.nluug.nl/programming/languages/abc)}, {FTP uunet (ftp://ftp.uu.net/languages/abc)}. Mailing list: . E-mail: . ["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. Argument, Basic value, C?. An {abstract machine} for implementation of {functional language}s and its intermediate code. [P. Koopman, "Functional Programs as Executable Specifications", 1990]. (1995-02-09)

ABC ALGOL 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)

ABCL/1 An Object-Based Concurrent Language. The language for the {ABCL} {MIMD} system, written by Akinori Yonezawa of Department of Information Science, {Tokyo University} in 1986. ABCL/1 uses {asynchronous} {message passing} to {object}s. 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: An Object-Oriented Concurrent System", A. Yonezawa ed, MIT Press 1990]. (1990-05-23). (1995-02-09)

ABCL/c+ 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)

ABCL/R 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)

ABCL/R2 An {object-oriented}, {concurrent}, {reflective} language based on {Hybrid Group Architecture}. ABCL/R2 was produced by , , , , 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)

abduction 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 ]. (2000-12-07)

ABEND /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 grinder}s. 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". [{Jargon File}] (1994-11-08)

ABI {Application Binary Interface}

ABLE 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)

ABM {Asynchronous Balanced Mode}

ABNF {Augumented Backus-Naur Form}

abort 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)

ABP 1. {Alternating bit protocol}. 2. {Microsoft} {Address Book Provider}. (2001-02-11)

ABR {automatic baud rate detection}

abscissa The x coordinate on an (x, y) graph; the input of a function against which the output is plotted. y is the "{ordinate}". See {Cartesian coordinates}. (1997-07-08)

ABSET 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)

absolute path A {path} relative to the {root directory}. Its first character must be the {pathname separator}. (1996-11-21)

absolute pathname A {pathname} relative to the {root directory}. (1996-11-21)

abstract class 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)

abstract data type (ADT) A type whose internal form is hidden behind a set of {access function}s. Objects 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. Abstract data types are central to {object-oriented programming} where every {class} is an ADT. 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. (1995-02-22)

abstract interpretation 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#

abstract machine 1. 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 {platform}s. 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. 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)

Abstract Machine Notation (AMN) A language for specifying {abstract machines} in the {B-Method}, based on the mathematical theory of {Generalised Substitutions}. (1995-03-13)

abstract syntax A representation of data (typically either a message passing over a communications link or a program being compiled) which is independent of machine-oriented structures and encodings and also of the physical representation of the data (called "{concrete syntax}" in the case of compilation or "{transfer syntax}" in communications). A {compiler}'s internal representation of a program will typically be specified by an abstract syntax 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)

Abstract Syntax Notation 1 (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 1998 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 {PDU}s 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}. (2000-10-20)

abstract syntax tree (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)

Abstract Window Toolkit (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]. {Home (http://java.sun.com/products/jdk/awt/)}. (2000-07-26)

Abstract Windowing Toolkit {Abstract Window Toolkit}

abstraction 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. Parameterisation, making something a function of something else. Examples are {lambda abstractions} (making a term into a function of some variable), {higher-order function}s (parameters are functions), {bracket abstraction} (making a term into a function of a variable). Opposite of {concretisation}. (1998-06-04)

Abstract-Type and Scheme-Definition Language (ASDL) A language developed as part of {Esprit} project {GRASPIN}, as a basis for generating {language-based editor}s 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)

ABSYS 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)

ACA {Application Control Architecture}

ACAP {Application Configuration Access Protocol}

Accelerated Graphics Port (AGP) A bus specification by {Intel} which gives low-cost 3D {graphics cards} faster access to {main memory} on {personal computers} than the usual PCI bus. AGP dynamically allocates the PC's normal RAM to store the screen image and to support {texture mapping}, {z-buffering} and {alpha blending}. Intel has built AGP into a {chipset} for its {Pentium II} microprocessor. AGP cards are slightly longer than a PCI card. AGP operates at 66 {MHz}, doubled to 133 MHz, compared with PCI's 33 Mhz. AGP allows for efficient use of {frame buffer} memory, thereby helping 2D graphics performance as well. AGP provides a coherent memory management design which allows scattered data in system memory to be read in rapid bursts. AGP reduces the overall cost of creating high-end graphics subsystems by using existing system memory. {AGP Implementors Forum AGP FAQ (http://www.agpforum.org/faq_ans.htm)}. {Specification (http://developer.intel.com/pc-supp/platform/agfxport/)}. {Intel AGP news (http://developer.intel.com/solutions/tech/agp.htm)}. (1999-01-08)

accelerator Additional hardware to perform some function faster than is possible in software running on the normal {CPU}. Examples include {graphics accelerator}s and {floating-point accelerator}s. (1994-11-08)

Accent A very high level interpreted language from {CaseWare, Inc.} with strings and tables. It is {strongly typed} and has remote function calls. (1994-11-08)

accept {Berkeley} {Unix} networking {socket} library routine to satisfy a connection request from a remote {host}. A specified socket on the local host (which must be capable of accepting the connection) is connected to the requesting socket on the remote host. The remote socket's socket address is returned. {Unix manual pages}: accept(2), connect(2). (1994-11-08)

Acceptable Use Policy (AUP) Rules applied by many {transit network}s which restrict the use to which the network may be put. A well known example is {NSFNet} which does not allow commercial use. Enforcement of AUPs varies with the network. (1994-11-08)

Acceptance, Test Or Launch Language (ATOLL) The language used for automating the checking and launch of Saturn rockets. ["SLCC ATOLL User's Manual", IBM 70-F11-0001, Huntsville AL Dec 1970]. (2000-04-03)

acceptance testing Formal testing conducted to determine whether a system satisfies its acceptance criteria and thus whether the customer should accept the system. (1996-05-10)

acceptor {Finite State Machine}

Access 1. An English-like query language used in the {Pick} {operating system}. 2. {Microsoft Access}. (1994-11-08)

Access Control List (ACL) A list of the services available on a {server}, each with a list of the {host}s permitted to use the service. (1994-11-08)

access method 1. The way that network devices access the network medium. 2. Software in an {SNA} processor that controls the flow of data through a {network}. [{physical layer}?] (1998-03-02)

access permission {permission}

access time The average time interval between a storage peripheral (usually a {disk drive} or {semiconductor} memory) receiving a request to read or write a certain location and returning the value read or completing the write. (1997-06-14)

ACCLAIM A European Union {ESPRIT} {Basic Research Action}. [What's it about?] (1994-11-08)

Accounting File A file which holds records of the resources used by individual jobs. These records are used to regulate, and calculate charges for, resources. An entry is opened in the accounting file as each job begins. (1996-12-08)

accounting management The process of identifying individual and group access to various network resources to ensure proper access capabilities ({bandwidth} and security) or to properly charge the various individuals and departments. Accounting management is one of five categories of {network management} defined by {ISO} for management of {OSI} {networks}. (1997-05-05)

ACCU {Association of C and C++ Users}

accumulator In a {central processing unit}, a {register} in which intermediate results are stored. Without an accumulator, it would be necessary to write the result of each calculation (addition, multiplication, {shift}, etc.) to {main memory} and read them back. Access to main memory is slower than access to the accumulator which usually has direct paths to and from the {arithmetic and logic unit} (ALU). The {canonical} example is summing a list of numbers. The accumulator is set to zero initially, each number in turn is added to the value in the accumulator and only when all numbers have been added is the result written to main memory. Modern CPUs usually have many registers, all or many of which can be used as accumulators. For this reason, the term "accumulator" is somewhat archaic. Use of it as a synonym for "register" is a fairly reliable indication that the user has been around for quite a while and/or that the architecture under discussion is quite old. The term in full is almost never used of microprocessor registers, for example, though symbolic names for arithmetic registers beginning in "A" derive from historical use of the term "accumulator" (and not, actually, from "arithmetic"). Confusingly, though, an "A" register name prefix may also stand for "address", as for example on the {Motorola} {680x0} family. 2. A register, memory location or variable being used for arithmetic or logic (as opposed to addressing or a loop index), especially one being used to accumulate a sum or count of many items. This use is in context of a particular routine or stretch of code. "The FOOBAZ routine uses A3 as an accumulator." [{Jargon File}] (1999-04-20)

accuracy How close to the real value a measurement is. Compare {precision}. (1998-04-19)

ACE 1. {Advanced Computing Environment}. 2. {Adaptive Communication Environment}.

ACF {Advanced Communications Function}

ACF/NCP {Advanced Communication Function/Network Control Program}

ACIA {Asynchronous Communications Interface Adapter}

ACID A {mnemonic} for the properties a transaction should have to satisfy the {Object Management Group} {Transaction Service} specifications. A transaction should be {Atomic}, its result should be Consistent, Isolated (independent of other transactions) and Durable (its effect should be permanent). The {Transaction Service} specifications which part of the {Object Services}, an adjunct to the {CORBA} specifications. (1997-05-15)

ACIS Andy, Charles, Ian's System. A {geometric engine} that most {CAD} packages now use. ACIS uses a sophisticated {object-oriented} approach for modelling, the data is stored in {boundary representation}. Acis is owned by {Spatial Technologies}. [How does this differ from "solid modelling"?]. (1996-03-21)

ACK 1. /ak/ The {mnemonic} for the ACKnowledge character, {ASCII} code 6. 2. A message transmitted to indicate that some data has been received correctly. Typically, if the sender does not receive the ACK message after some predetermined time, or receives a {NAK}, the original data will be sent again. [{Jargon File}] (1997-01-07)

ACL 1. {Access Control List}. 2. {Association for Computational Linguistics}. 3. A Coroutine Language. A {Pascal}-based implementation of {coroutine}s. ["Coroutines", C.D. Marlin, LNCS 95, Springer 1980]. (1994-11-08)

ACM 1. The {Association for Computing}. 2. {addressed call mode}. (1997-05-07)

ACME /ak'mee/ 1. A Company that Makes Everything. The {canonical} imaginary business. Possibly also derived from the word "acme" meaning "highest point". 2. A program for {MS-DOS}. [What does it do?] (1994-11-08)

ACOM An early system on the {IBM 705}. [Listed in CACM 2(5):16 (May 1959)]. (1994-11-08)

Acorn Archimedes {Archimedes}

Acorn Computer Group A holding company for {Acorn Computers} Limited, Acorn Australia, Acorn New Zealand, Acorn GmbH and {Online Media}. Acorn Computer Group owns 43% of {Advanced RISC Machines} Ltd. (1994-11-08)

Acorn Computers Ltd. A UK computer manufacturer, part of the {Acorn Computer Group} plc. Acorn was founded on 1978-12-05, on a kitchen table in a back room. Their first creation was an electronic slot machine. After the {Acorn System 1}, 2 and 3, Acorn launched the first commercial {microcomputer} - the {ATOM} in March 1980. In April 1981, Acorn won a contract from the {BBC} to provide the {PROTON}. In January 1982 Acorn launched the {BBC Microcomputer} System. At one time, 70% of microcomputers bought for UK schools were BBC Micros. The Acorn Computer Group went public on the Unlisted Securities Market in September 1983. In April 1984 Acorn won the Queen's Award for Technology for the BBC Micro and in September 1985 {Olivetti} took a controlling interest in Acorn. The {Master} 128 Series computers were launched in January 1986 and the BBC {Domesday} System in November 1986. In 1983 Acorn began to design the Acorn RISC Machine (ARM), the first low-cost, high volume {RISC} processor chip (later renamed the {Advanced RISC Machine}). In June 1987 they launched the {Archimedes} range - the first 32-bit {RISC} based {microcomputers} - which sold for under UKP 1000. In February 1989 the R140 was launched. This was the first {Unix} {workstation} under UKP 4000. In May 1989 the A3000 (the new {BBC Microcomputer}) was launched. In 1990 Acorn formed {Advanced RISC Machines} Ltd. (ARM) in partnership with {Apple Computer, Inc.} and {VLSI} to develop the ARM processor. Acorn has continued to develop {RISC} based products. With 1992 revenues of 48.2 million pounds, Acorn Computers was the premier supplier of {Information Technology} products to UK education and had been the leading provider of 32-bit RISC based {personal computers} since 1987. Acorn finally folded in the late 1990s. Their operating system, {RISC OS} was further developed by a consortium of suppliers. {Usenet} newsgroups: {news:comp.sys.acorn}, {news:comp.sys.acorn.announce}, {news:comp.sys.acorn.tech}, {news:comp.binaries.acorn}, {news:comp.sources.acorn}, {news:comp.sys.acorn.advocacy}, {news:comp.sys.acorn.games}. {Acorn's FTP server (ftp://ftp.acorn.co.uk/)} {HENSA software archive (http://micros.hensa.ac.uk/micros/arch.html)}. {Richard Birkby's Acorn page (http://www.csv.warwick.ac.uk/~phudv/)}. {RiscMan's Acorn page (http://www.geko.com.au/riscman/)}. {Acorn On The Net (http://www.stir.ac.uk/~rhh01/Main.html)}. {"The Jungle" by Simon Truss (http://www.csc.liv.ac.uk/users/u1smt/u1smt.html)}. [Recent history?] (2000-09-26)

Acorn RISC Machine The original name of the {Advanced RISC Machine}. (1995-03-07)

ACOS A {BBS} language for {PRODOS 8} on {Apple II}. {Macos} is a hacked version of ACOS. (1994-11-08)

acoustic coupler A device used to connect a {modem} to a telephone line via an ordinary handset. The acoustic coupler converts electrical signals from the {modem} to sound via a loudspeaker, against which the mouthpiece of a telephone handset is placed. The earpiece is placed against a microphone which converts sound to electrical signals which return to the modem. The handset is inserted into a sound-proof box containing the louspeaker and microphone to avoid interference from ambient noise. Acousitic couplers are now rarely used since most modems have a direct electrical connection to the telephone line. This avoids the signal degradation caused by conversion to and from audio. Direct connection is not always possible, and was actually illegal in the United Kingdom before {British Telecom} was privatised. BT's predecessor, the General Post Office, did not allow subscribers to connect their own equipment to the telephone line. (1994-11-08)