Editing SECD machine (section)

{{Short description|Abstract machine as a target for compilers}}
{{Infobox software
| title = SECD machine
| logo = <!-- File name without 'File:' -->
| logo caption = 
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| author = [[Peter Landin]]
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| released = {{Start date and age|1964}}
| discontinued = Yes
| latest release version = 
| latest release date = <!-- {{Start date and age|196y|mm|dd|df=yes}} -->
| programming language = 
| operating system = [[Linux]], [[Microsoft Windows|Windows]], [[DOS]]
| platform = [[Free Pascal]] on [[IA-32]], [[x86-64]]
| included with = [[Lispkit Lisp]], [[Lisp (programming language)|Lisp]]/[[IBM System/370|370]], pure_LISP
| size = ~ 76K, 185K, 920K
| language = English
| genre = [[Virtual machine|virtual]] and [[abstract machine]]
| license = <!-- or |licence= -->
| website = {{URL|skelet.ludost.net/sec}}
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The '''SECD machine''' is a highly influential (see: ''[[#Landin's contribution|Landin's contribution]]'') [[virtual machine]] and [[abstract machine]] intended as a target for [[compiler]]s of [[Functional programming|functional]] [[programming language]]s. The letters stand for <code>stack</code>, <code>environment</code>, <code>control</code>, <code>dump</code>, respectively, which are the [[Processor register|internal registers]] of the machine. The registers <code>stack</code>, <code>control</code>, and <code>dump</code> point to (some realizations of) [[Stack (abstract data type)|stacks]], and <code>environment</code> points to (some realization of) an [[associative array]].

The machine was the first to be specifically designed to evaluate [[lambda calculus]] expressions. It was originally described by [[Peter Landin]] in "The Mechanical Evaluation of Expressions" in 1964.<ref>{{Cite journal |last1=Landin |first1=P. J. |author1-link=Peter Landin |date=January 1964 |title=The Mechanical Evaluation of Expressions |doi=10.1093/comjnl/6.4.308 |journal=[[The Computer Journal]] |volume=6 |issue=4 |pages=308–320 |doi-access=free}}</ref> The description published by Landin was fairly abstract, and left many implementation choices open (like an [[operational semantics]]).

[[Lispkit Lisp]] was an influential compiler based on the SECD machine,<ref>{{cite book |last1=Henderson |first1=Peter |date=1980 |title=Functional programming: application and implementation |publisher=Prentice-Hall International |location=Englewood Cliffs, New Jersey |isbn=0-13-331579-7}}</ref> and the SECD machine has been used as the target for other systems such as [[Lisp (programming language)|Lisp]]/[[IBM System/370|370]].<ref>{{cite conference |last1=Padget |first1=Julian |date=1988 |title=Three uncommon Lisps |publisher=School of Mathematical Sciences, University of Bath |conference=First International Workshop on Lisp Evolution and Standardization |publication-place=Bath, Avon, United Kingdom |url=https://www.softwarepreservation.org/projects/LISP/conference/iwoleas88/Padget-ThreeUncommonLisps.pdf |citeseerx=<!-- dead? 10.1.1.99.1028 --> |via=[[Computer History Museum]]}}</ref> In 1989, researchers at the [[University of Calgary]] worked on a hardware implementation of the machine, with the same rationale as a [[high-level language computer architecture]] related to a [[Lisp machine]].<ref>{{cite report |last1=Graham |first1=Brian |date=1 September 1989 |url=http://hdl.handle.net/1880/46590 |title=SECD: Design Issues |place=Calgary, Alberta, Canada |access-date=12 December 2024}}</ref>