MDL (Model Development Language, or colloquially also referred to as More Datatypes than Lisp or MIT Design Language) is a

programming language A programming language is a system of notation for writing computer programs. Most programming languages are text-based formal languages, but they may also be graphical. They are a kind of computer language. The description of a programming ...

, a descendant of the language

Lisp A lisp is a speech impairment in which a person misarticulates sibilants (, , , , , , , ). These misarticulations often result in unclear speech. Types * A frontal lisp occurs when the tongue is placed anterior to the target. Interdental lisping ...

. Its initial purpose was to provide high level language support for the Dynamic Modeling Group at

Massachusetts Institute of Technology The Massachusetts Institute of Technology (MIT) is a private land-grant research university in Cambridge, Massachusetts. Established in 1861, MIT has played a key role in the development of modern technology and science, and is one of the ...

's (MIT)

Project MAC Computer Science and Artificial Intelligence Laboratory (CSAIL) is a research institute at the Massachusetts Institute of Technology (MIT) formed by the 2003 merger of the Laboratory for Computer Science (LCS) and the Artificial Intelligence Lab ...

. It was developed in 1971 on a

PDP-10 Digital Equipment Corporation (DEC)'s PDP-10, later marketed as the DECsystem-10, is a mainframe computer family manufactured beginning in 1966 and discontinued in 1983. 1970s models and beyond were marketed under the DECsystem-10 name, especi ...

running ITS and later ran on TENEX,

TOPS-20 The TOPS-20 operating system by Digital Equipment Corporation (DEC) is a proprietary OS used on some of DEC's 36-bit mainframe computers. The Hardware Reference Manual was described as for "DECsystem-10/DECSYSTEM-20 Processor" (meaning the DEC PDP- ...

BSD The Berkeley Software Distribution or Berkeley Standard Distribution (BSD) is a discontinued operating system based on Research Unix, developed and distributed by the Computer Systems Research Group (CSRG) at the University of California, Berk ...

, and

AEGIS The aegis ( ; grc, αἰγίς ''aigís''), as stated in the ''Iliad'', is a device carried by Athena and Zeus, variously interpreted as an animal skin or a shield and sometimes featuring the head of a Gorgon. There may be a connection with a d ...

. The initial development team consisted of

Gerald Sussman Gerald Jay Sussman (born February 8, 1947) is the Panasonic Professor of Electrical Engineering at the Massachusetts Institute of Technology (MIT). He received his S.B. and Ph.D. degrees in mathematics from MIT in 1968 and 1973 respectively. H ...

and

Carl Hewitt Carl Eddie Hewitt () is an American computer scientist who designed the Planner programming language for automated planningCarl Hewitt''PLANNER: A Language for Proving Theorems in Robots''IJCAI. 1969. and the actor model of concurrent computing, ...

of the Artificial Intelligence Lab, and Chris Reeve,

Bruce Daniels Bruce Daniels is an American hydroclimatologist, business executive and computer programmer. He is known in Silicon Valley as one of the pioneers of the personal computer and user-friendly interfaces. Daniels earned his Ph.D. from the Universi ...

, and David Cressey of the Dynamic Modeling Group. Later, Stu Galley, also of the Dynamic Modeling Group, wrote the MDL documentation. MDL was initially called ''Muddle''. This style of self-deprecating humor was not widely understood or appreciated outside of Project MAC. So the name was sanitized to MDL. MDL provides several enhancements to classic Lisp. It supports several built-in data types, including lists, strings and arrays, and user-defined data types. It offers multithreaded expression evaluation and

coroutine Coroutines are computer program components that generalize subroutines for non-preemptive multitasking, by allowing execution to be suspended and resumed. Coroutines are well-suited for implementing familiar program components such as cooperative ...

Variable Variable may refer to: * Variable (computer science), a symbolic name associated with a value and whose associated value may be changed * Variable (mathematics), a symbol that represents a quantity in a mathematical expression, as used in many ...

s can carry both a local value within a scope, and a global value, for passing data between scopes. Advanced built-in functions supported interactive

debugging In computer programming and software development, debugging is the process of finding and resolving '' bugs'' (defects or problems that prevent correct operation) within computer programs, software, or systems. Debugging tactics can involve in ...

of MDL programs, incremental

development Development or developing may refer to: Arts *Development hell, when a project is stuck in development *Filmmaking, development phase, including finance and budgeting *Development (music), the process thematic material is reshaped * Photograph ...

, and reconstruction of source programs from object programs. Although MDL is obsolete, some of its features have been incorporated in later versions of Lisp. Gerald Sussman went on to develop the

Scheme A scheme is a systematic plan for the implementation of a certain idea. Scheme or schemer may refer to: Arts and entertainment * ''The Scheme'' (TV series), a BBC Scotland documentary series * The Scheme (band), an English pop band * ''The Schem ...

language, in collaboration with

Guy Steele Guy Lewis Steele Jr. (; born October 2, 1954) is an American computer scientist who has played an important role in designing and documenting several computer programming languages and technical standards. Biography Steele was born in Missouri ...

, who later wrote the specifications for

Common Lisp Common Lisp (CL) is a dialect of the Lisp programming language, published in ANSI standard document ''ANSI INCITS 226-1994 (S20018)'' (formerly ''X3.226-1994 (R1999)''). The Common Lisp HyperSpec, a hyperlinked HTML version, has been derived fro ...

and

Java Java (; id, Jawa, ; jv, ꦗꦮ; su, ) is one of the Greater Sunda Islands in Indonesia. It is bordered by the Indian Ocean to the south and the Java Sea to the north. With a population of 151.6 million people, Java is the world's List ...

. Carl Hewitt had already published the idea for the language ''

Planner Planner may refer to: * A personal organizer (book) for planning * Microsoft Planner * Planner programming language * Planner (PIM for Emacs) * Urban planner * Route planner * Meeting and convention planner * Japanese term for video game designer ...

'' before the MDL project began, but his subsequent thinking on Planner reflected lessons learned from building MDL. Planner concepts influenced languages such as

Prolog Prolog is a logic programming language associated with artificial intelligence and computational linguistics. Prolog has its roots in first-order logic, a formal logic, and unlike many other programming languages, Prolog is intended primarily ...

and

Smalltalk Smalltalk is an object-oriented, dynamically typed reflective programming language. It was designed and created in part for educational use, specifically for constructionist learning, at the Learning Research Group (LRG) of Xerox PARC by Alan Ka ...

. Smalltalk and

Simula Simula is the name of two simulation programming languages, Simula I and Simula 67, developed in the 1960s at the Norwegian Computing Center in Oslo, by Ole-Johan Dahl and Kristen Nygaard. Syntactically, it is an approximate superset of ALGOL 6 ...

, in turn, influenced Hewitt's future work on the actor model. But the largest influence that MDL had was on the

software Software is a set of computer programs and associated documentation and data. This is in contrast to hardware, from which the system is built and which actually performs the work. At the lowest programming level, executable code consists ...

genre of

interactive fiction '' Interactive fiction, often abbreviated IF, is software simulating environments in which players use text commands to control characters and influence the environment. Works in this form can be understood as literary narratives, either in the ...

(IF). An IF game named

Zork ''Zork'' is a text-based adventure game first released in 1977 by developers Tim Anderson, Marc Blank, Bruce Daniels, and Dave Lebling for the PDP-10 mainframe computer. The original developers and others, as the company Infocom, expanded a ...

, sometimes called Dungeon, was first written in MDL. Later, Reeve, Daniels, Galley and other members of Dynamic Modeling went on to start

Infocom Infocom was an American software company based in Cambridge, Massachusetts, that produced numerous works of interactive fiction. They also produced a business application, a relational database called ''Cornerstone (software), Cornerstone''. ...

, a company that produced many early

commercial Commercial may refer to: * a dose of advertising conveyed through media (such as - for example - radio or television) ** Radio advertisement ** Television advertisement * (adjective for:) commerce, a system of voluntary exchange of products and s ...

works of interactive fiction. In 1980

Marc Blank Marc Blank is an American game developer and software engineer. He is best known as part of the team that created one of the first commercially successful text adventure computer games, ''Zork''. Career Blank first encountered Don Woods and Will ...

and Joel Berez adapted the MDL language to create a subset called

ZIL (Zork Implementation Language) ZIL or Zil may refer to: * ZiL (''Zavod imeni Likhachova''), a former car and truck factory in Moscow, Russia ** ZiL lanes, dedicated traffic lanes for Soviet officials * ZIL (Moscow Central Circle), a Moscow Metro railway station * Zil, Iran, a ...

which was used extensively by

to create their award winning games.

Code sample

This is a sample of PDP-10 MDL: EST ROOM) ) ) ( > ) ( .RMS>> ) ( .RMS> .RMS>>> )>> .EXITS>>

References

External links

{{DEFAULTSORT:Mdl (Programming Language) Dynamically typed programming languages Functional languages Lisp programming language family

Code sample

See also

References

External links