D. 1. "The Data Language." {MS-DOS} 4GL. 2. A {Haskell}-like language, with {type class}es. E-mail: . DAA. Distributed Application Architecture: under design by Hewlett-Packard and Sun. A distributed object management environment that will allow applications to be developed independent of operating system, network or windowing system. DAC. {Digital to Analog Converter} DACAPO. Broad-range hardware specification language. "Mixed Level Modelling and Simulation of VLSI Systems", F.J. Rammig in Logic Design and Simulation, E. Horbst ed, N-H 1986. DACNOS. A prototype network operating system for multi-vendor environments, from IBM European Networking Centre Heidelberg and University of Karlsruhe. (1995-01-16) D/A converter. {Digital to Analog Converter} DACTL. Declarative Alvey Compiler Target Language. An intermediate language from the {University of East Anglia}, used in the {Flagship} project. DACTL is based on a form of {graph rewriting} which can be used to implement {functional language}s, {logic language}s and {imperative} languages. The current version is Dactl0. ["DACTL - A Computational Model and Compiler Target Language Based on Graph Reduction", J.R.W. Glauert et al, ICL Tech J 5(3) (1987)]. (1994-09-22) DADS. {Dictionary of Algorithms and Data Structures} daemon. /day'mn/ or /dee'mn/ (From the mythological meaning, later rationalised as the acronym "Disk And Execution MONitor") A program that is not invoked explicitly, but lies dormant waiting for some condition(s) to occur. The idea is that the perpetrator of the condition need not be aware that a daemon is lurking (though often a program will commit an action only because it knows that it will implicitly invoke a daemon). For example, under {ITS} writing a file on the {LPT} spooler's directory would invoke the spooling daemon, which would then print the file. The advantage is that programs wanting files printed need neither compete for access to, nor understand any idiosyncrasies of, the {LPT}. They simply enter their implicit requests and let the daemon decide what to do with them. Daemons are usually spawned automatically by the system, and may either live forever or be regenerated at intervals. {Unix} systems run many daemons, chiefly to handle requests for services from other {host}s on a {network}. Most of these are now started as required by a single real daemon, {inetd}, rather than running continuously. Examples are {cron} (local timed command execution), {rshd} (remote command execution), {rlogind} and {telnetd} (remote login), {ftpd}, {nfsd} (file transfer), {lpd} (printing). Daemon and {demon} are often used interchangeably, but seem to have distinct connotations (see {demon}). The term "daemon" was introduced to computing by {CTSS} people (who pronounced it /dee'mon/) and used it to refer to what {ITS} called a {dragon}. [{Jargon File}] (1995-05-11) DAG. 1. {Data Address Generator}. 2. {directed acyclic graph}. (1997-08-30)
