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{{Short description|Early programming language for lists}}
{{More citations needed|date=January 2022}}
{{Infobox programming language
| name = Information Processing Language (IPL)
Line 6 ⟶ 8:
| designer =[[Allen Newell]], [[Cliff Shaw]], [[Herbert A. Simon]]
| developer =Allen Newell, Cliff Shaw, Herbert A. Simon
| latest_release_version =IPL-VIV
| latest release date = <!-- {{start date and age|1959?|MM|DD|df=yes}} -->
| typing =
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| file_ext =
}}
'''Information Processing Language''' ('''IPL''') is a [[programming language]] created by [[Allen Newell]], [[Cliff Shaw]], and [[Herbert A. Simon]] at [[RAND Corporation]] and the [[Carnegie Institute of Technology]] at about 1956. Newell had the job of language specifier-application programmer, Shaw was the system programmer, and Simon tookhad the job of application programmer-user.
 
TheIPL language includesincluded features intended to helpfacilitate withAI programsprogramming, that perform simplespecifically [[Problem_solving|problem solving actions]]. such as lists, [[dynamic memory allocation]], [[data type]]s, [[Recursion (computer science)|recursion]], [[Subroutine|functions]] as arguments, generators, and [[cooperative multitasking]]. IPL inventedalso introduced the conceptconcepts of [[Symbolic_language_(programming)|symbol processing]] and list processing. Unfortunately, albeitall of these innovations were cast in ana difficult [[Assembly language|assembly-language]] style. Nontheless, IPL-V (the only public version of IPL) ran on many computers through the mid 1960s.
 
==A tasteBasics of IPL==
An IPL computer has:
 
# A set of ''symbols''. All symbols are addresses, and name cells. Unlike symbols in later languages, symbols consist of a character followed by a number, and are written H1, A29, 9–7, 9–100.
An IPL computer has:
 
# a set of ''symbols''. All symbols are addresses, and name cells. Unlike symbols in later languages, symbols consist of a character followed by a number, and are written H1, A29, 9-7, 9-100.
## Cell names beginning with a letter are ''regional'', and are absolute addresses.
## Cell names beginning with "9-" are ''local'', and are meaningful within the context of a single list. One list's 9-1 is independent of another list's 9-19–1.
## Other symbols (e.g., pure numbers) are ''internal''.
# aA set of ''cells''. Lists are builtmade from several cells holdingincluding mutual references. Cells have several fields:
## P, a 3-bit field used for an operation code when the cell is used as an instruction, and unused when the cell is data.
## Q, a 3-valued field used for indirect reference when the cell is used as an instruction, and unused when the cell is data.
## SYMB, a symbol used as the value in the cell.
# aA set of ''primitive processes'', which would be termed ''primitive functions'' in modern languages.
 
The data structure of IPL is the list, but lists are more intricate structures than in many languages. A list consists of a singly linked sequence of symbols, as might be expected -- plusexpected—plus some ''description lists'', which are subsidiary singly linked lists interpreted as alternating attribute names and values. IPL provides primitives to access and mutate attribute value by name. The description lists are given local names (of the form 9-19–1). So, a list callednamed L1 holdingcontaining the symbols S4 and S5, and described by associating value V1 to attribute A1 and V2 to A2, would be stored as follows. 0 indicates the end of a list; the cell names 100, 101, etc. are automatically generated internal symbols whose values are irrelevant. These cells can be scattered throughout memory; only L1, which uses a regional name that must be globally known, needs to reside in a specific place.
 
{|style="font-family:monospace; margin: 1em auto" class="wikitable"
<code>
|+ IPL-V List Structure Example
{|
|+ '''IPL-V List Structure Example'''
|-
!Name !! SYMB !! LINK
Line 60:
|203 || V2 || 0
|}
</code>
 
IPL is an [[assembly language]] for manipulating lists. It has a few cells which are used as special-purpose registers. H1, for example, is the program counter. The SYMB field of H1 is the name of the current instruction. However, H1 is interpreted as a list; the LINK of H1 is, in modern terms, a pointer to the headbeginning of the call stack. For example, subroutine calls push the SYMB of H1 onto this stack.
 
H2 is the free-list. Procedures which need to allocate memory grab cells off of H2; procedures which are finished with memory put it on H2. On entry to a function, the list of parameters is given in H0; on exit, the results should be returned in H0. Many procedures return a boolean result indicating success or failure, which is put in H5. Ten cells, W0-W9, are reserved for public working storage. Procedures are "morally bound" (to quote the CACM article) to save and restore the values of these cells.
Line 68 ⟶ 67:
There are eight instructions, based on the values of P: subroutine call, push/pop S to H0; push/pop the symbol in S to the list attached to S; copy value to S; conditional branch. In these instructions, S is the target. S is either the value of the SYMB field if Q=0, the symbol in the cell named by SYMB if Q=1, or the symbol in the cell named by the symbol in the cell named by SYMB if Q=2. In all cases but conditional branch, the LINK field of the cell tells which instruction to execute next.
 
IPL has a library of some 150 basic operations. These include such operations as:
 
* Test symbols for equality
* Find, set, or erase an attribute of a list
* locateLocate the next symbol in a list; insert a symbol in a list; erase or copy an entire list.
* Arithmetic operations (on symbol names).
* Manipulation of symbols; e.g., test if a symbol denotes an integer, or make a symbol local.
* I/O operations
* "generatorsGenerators", which correspond to iterators and filters in functional programming. For example, a generator may accept a list of numbers and produce the list of their squares. Generators could accept suitably designed functions – strictlyfunctions—strictly, the addresses of code of suitably designed functions – asfunctions—as arguments.
 
== History ==
IPL was first utilized to demonstrate that the theorems in ''[[Principia Mathematica]]'' which were laboriously proven laboriously by hand, by [[Bertrand Russell]] and [[Alfred North Whitehead]], could in fact be [[automated theorem proving|proven by computation]]. According to Simon's autobiography ''Models of My Life'', this application was originally developed first by hand simulation, using his children as the computing elements, while writing on and holding up note cards as the registers which contained the state variables of the program.
 
IPL was used to implement several early [[artificial intelligence]] programs, also by the same authors: the [[Logic Theorist]] (1956), the [[General Problem Solver]] (1957), and their [[computer chess]] program [[NSS (chess program)|NSS]] (1958).
 
Several versions of IPL were created: IPL-I (never implemented), IPL-II (1957 for [[JOHNNIAC]]), IPL-III (existed briefly), IPL-IV, IPL-V (1958, for [[IBM 650]], [[IBM 704]], [[IBM 7090]], [[Philco model 212]], many others. Widely used),. IPL-VI was a proposal for an IPL hardware.<ref>{{FOLDOC|Information+Processing+Language}}</ref>{{sfn|Shaw|Newell|Simon|Ellis|1958}}{{sfn|Sammet|1969|p=389}}
 
A co-processor “IPL-VC” for the CDC 3600 at Argonne National Libraries was developed which could run IPL-V commands.{{sfn|Hodges|1964}}{{sfn|Sammet|1969|p=393–394}} It was used to implement another checker-playing program.{{sfn|Cowell|Reed|1965}} This hardware implementation did not improve running times sufficiently to “compete favorably with a language more directly oriented to the structure of present-day machines”.{{sfn|Carson|Robinson|1966|p=5}}
However the language was soon displaced by [[Lisp programming language|Lisp]], which had far more powerful features, a simpler syntax, and the benefit of automatic [[garbage collection (computer science)|garbage collection]].
 
IPL was soon displaced by [[Lisp (programming language)|Lisp]], which had much more powerful features, a simpler syntax, and the benefit of automatic [[garbage collection (computer science)|garbage collection]].
== Legacy to computer programming ==
IPL arguably introduced several programming language features:
* ''List manipulation'' – but only lists of atoms, not general lists
* ''Property lists'' – but only when attached to other lists
* ''Higher-order functions'' – except that assembly programming has always been able to compute with addresses of functions to call; IPL was an early attempt to generalize this property of assembly language and in a principled way
* ''Computation with symbols'' – except that the symbols are letter+number, not full words
* ''Virtual machine''
 
==Legacy to computer programming==
Many of these features were generalized, cleaned up, and incorporated into Lisp<ref>[http://www-formal.stanford.edu/jmc/history/lisp/node2.html John McCarthy (1979) ''History of Lisp'' "LISP prehistory - Summer 1956 through Summer 1958."]</ref> and from there into a wide range of programming languages over the next several decades.
IPL arguably introduced several programming language features:
* ''List manipulation''—but only lists of atoms, not general lists
* ''Property lists''—but only when attached to other lists
* ''Higher-order functions''—while assembly programming had always allowed computing with the addresses of functions, IPL was an early attempt to generalize this property of assembly language in a principled way
* ''Computation with symbols''—though symbols have a restricted form in IPL (letter followed by number)
* ''Virtual machine''
 
Many of these features were generalized, rationalized, and incorporated into Lisp<ref>[http://www-formal.stanford.edu/jmc/history/lisp/node2.html John McCarthy (1979) ''History of Lisp'' "LISP prehistory - Summer 1956 through Summer 1958."]</ref> and from there into many other programming languages during the next several decades.
== See also ==
* [[Lisp (programming language)|Lisp]]
 
==References==
{{Reflist}}
 
* {{FOLDOC}}
==Sources==
 
* {{cite report
|author1-first=Daniel F.
|author1-last=Carson
|author2-first=George A.
|author2-last=Robinson
|date=May 1966
|title=Gyro II, A Macro-Defined System for List Processing
|id=ANL-7149
|publisher=Applied Mathematics Division, Argonne National Laboratories}}
 
* {{cite report
|author1-first=W. R.
|author1-last=Cowell
|author2-first=M. C.
|author2-last=Reed
|date=October 1965
|title=A Checker-Playing Program for the IPL-VC Computer
|id=ANL-7109
|publisher=Applied Mathematics Division, Argonne National Laboratories}}
 
* {{cite report
|author-first=Donald
|author-last=Hodges
|date=May 1964
|title=IPL-VC: A Computer System having the IPL-V Instruction Set
|id=ANL-6888
|publisher=Applied Mathematics Division, Argonne National Laboratories}}
 
* {{cite book
|author-last=Sammet
|author-first=Jean E.
|title=Programming languages: history and fundamentals
|publisher=Prentice Hall
|___location=Englewood Cliffs, N.J.
|year=1969
|pages=388{{en dash}}400}}
 
* {{cite conference
|author1-last=Shaw
|author1-first=J. C.
|author2-last=Newell
|author2-first=A.
|author3-last=Simon
|author3-first=H. A.
|author4-last=Ellis
|author4-first=T. O.
|title=A Command Structure for Complex Information Processing
|date=1958
|publisher=Association for Computing Machinery
|isbn=9781450378642
|doi=10.1145/1457769.1457803
|book-title=Proceedings of the May 6–8, 1958, Western Joint Computer Conference: Contrasts in Computers
|series=IRE-ACM-AIEE '58 (Western)
|pages=119{{endash}}128}}
 
==Further reading==
 
*Newell, A. and F.C. Shaw. "Programming the Logic Theory Machine." Feb. 1957. Proceedings of the Western Joint Computer Conference, pp. 230-240.
* {{cite conference
*Newell, Allen, and Fred M. Tonge. 1960. "An Introduction to Information Processing Language V." CACM 3(4): 205-211.
|author-last1=Newell
*Newell, Allen. 1964. ''Information Processing Language-V Manual; Second Edition''. Rand Corporation [Allen Newell], Englewood Cliffs, NJ: Prentice-Hall.
|author-first1=Allen
*Samuel, Arthur L.: Programming Computers to Play Games. In: Advances in Computers, Vol. 1, 1960, pp 165-192 (esp.: 171-175).
|author-last2=Shaw
|author-first2=J. C.
|title=Programming the Logic Theory Machine
|year=1957
|publisher=Association for Computing Machinery
|isbn=9781450378611
|book-title=Papers Presented at the February 26–28, 1957, Western Joint Computer Conference: Techniques for Reliability
|pages=230–240
|conference=IRE-AIEE-ACM '57 (Western)
|doi=10.1145/1455567.1455606|doi-access=free
}}
 
* {{cite journal
|author-last1=Newell
|author-first1=Allen
|author-last2=Tonge
|author-first2=Fred M.
|title=An Introduction to Information Processing Language V
|year=1960
|publisher=Association for Computing Machinery
|___location=New York, NY, USA
|volume=3
|number=4
|issn=0001-0782
|doi=10.1145/367177.367205
|journal=Communications of the ACM
|pages=205–211|s2cid=16609075
|doi-access=free
}}
 
* {{cite book
|author-last1=Newell
|author-first1=Allen
|author-last2=Tonge
|author-first2=Fred M.
|author-last3=Feigenbaum
|author-first3=Edward A.
|author-last4=Green Jr.
|author-first4=Bert F.
|author-last5=Mealy
|author-first5=George H.
|display-authors=2
|title=Information Processing Language-V Manual
|publisher=Prentice Hall
|___location=Englewood Cliffs, N.J.
|year=1964}}
 
* {{cite book
|author-last=Samuel
|author-first=Arthur L.
|title=Advances in Computers Volume 1
|chapter=Programming Computers to Play Games
|volume=1
|editor-last=Alt
|editor-first=Franz L.
|publisher=Elsevier
|pages=165–192
|year=1960
|issn=0065-2458
|doi=10.1016/S0065-2458(08)60608-7|isbn=9780120121014
}}
 
==External links==
* [https://web.archive.org/web/20050101091320/http://stills.nap.edu/readingroom/books/biomems/anewell.html Allen Newell], Herbert A. Simon, "Biographical Memoirs", National Academy of Sciences - (includes a short section on IPL.)]
* [http://bitsavers.org/pdf/rand/ipl/] IPL documents from BitSavers.]
* [http://www-formal.stanford.edu/jmc/history/lisp/node2.html] influenceInfluence of IPL on LISP.]
* [https://github.com/jeffshrager/IPL-V A Common LISP interpreter for IPL-V, including a working transcription of the Logic Theory Machine (actively under development in 2025)]
 
{{Authority control}}
 
[[Category:Procedural programming languages]]
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