Information Processing Language
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Information Processing Language (IPL) 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 ...
created by
Allen Newell Allen Newell (March 19, 1927 – July 19, 1992) was a researcher in computer science and cognitive psychology at the RAND Corporation and at Carnegie Mellon University’s School of Computer Science, Tepper School of Business, and Department ...
,
Cliff Shaw John Clifford Shaw (February 23, 1922 – February 9, 1991) was a systems programmer at the RAND Corporation. He is a coauthor of the first artificial intelligence program, the Logic Theorist, and was one of the developers of General Problem Solve ...
, and
Herbert A. Simon Herbert Alexander Simon (June 15, 1916 – February 9, 2001) was an American political scientist, with a Ph.D. in political science, whose work also influenced the fields of computer science, economics, and cognitive psychology. His primary ...
at
RAND Corporation The RAND Corporation (from the phrase "research and development") is an American nonprofit global policy think tank created in 1948 by Douglas Aircraft Company to offer research and analysis to the United States Armed Forces. It is financed ...
and the
Carnegie Institute of Technology Carnegie Mellon University (CMU) is a private research university in Pittsburgh, Pennsylvania. One of its predecessors was established in 1900 by Andrew Carnegie as the Carnegie Technical Schools; it became the Carnegie Institute of Technology ...
about 1956. Newell had the job of language specifier-application programmer, Shaw was the system programmer, and Simon had the job of application programmer-user. The code includes features intended to help with programs that perform simple problem solving actions such as lists,
dynamic memory allocation Memory management is a form of resource management applied to computer memory. The essential requirement of memory management is to provide ways to dynamically allocate portions of memory to programs at their request, and free it for reuse when ...
,
data type In computer science and computer programming, a data type (or simply type) is a set of possible values and a set of allowed operations on it. A data type tells the compiler or interpreter how the programmer intends to use the data. Most progra ...
s,
recursion Recursion (adjective: ''recursive'') occurs when a thing is defined in terms of itself or of its type. Recursion is used in a variety of disciplines ranging from linguistics to logic. The most common application of recursion is in mathematics ...
, functions as arguments, generators, and
cooperative multitasking Cooperative multitasking, also known as non-preemptive multitasking, is a style of computer multitasking in which the operating system never initiates a context switch from a running process to another process. Instead, in order to run multiple ...
. IPL invented the concept of list processing, albeit in an assembly-language style.


Basics 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. ## 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 9-1. ## Other symbols (e.g., pure numbers) are ''internal''. # A set of ''cells''. Lists are made from several cells including 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. # A 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—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 9-1). So, a list named L1 containing 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. IPL is an
assembly language In computer programming, assembly language (or assembler language, or symbolic machine code), often referred to simply as Assembly and commonly abbreviated as ASM or asm, is any low-level programming language with a very strong correspondence be ...
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 beginning 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. 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 * Locate 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 * "Generators", 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—strictly, the addresses of code of suitably designed functions—as arguments.


History

IPL was first utilized to demonstrate that the theorems in ''
Principia Mathematica The ''Principia Mathematica'' (often abbreviated ''PM'') is a three-volume work on the foundations of mathematics written by mathematician–philosophers Alfred North Whitehead and Bertrand Russell and published in 1910, 1912, and 1913. ...
'' which were proven laboriously by hand, by
Bertrand Russell Bertrand Arthur William Russell, 3rd Earl Russell, (18 May 1872 – 2 February 1970) was a British mathematician, philosopher, logician, and public intellectual. He had a considerable influence on mathematics, logic, set theory, linguistics, ...
and
Alfred North Whitehead Alfred North Whitehead (15 February 1861 – 30 December 1947) was an English mathematician and philosopher. He is best known as the defining figure of the philosophical school known as process philosophy, which today has found applicat ...
, could in fact be 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 Artificial intelligence (AI) is intelligence—perceiving, synthesizing, and inferring information—demonstrated by machines, as opposed to intelligence displayed by animals and humans. Example tasks in which this is done include speech re ...
programs, also by the same authors: the
Logic Theorist Logic Theorist is a computer program written in 1956 by Allen Newell, Herbert A. Simon, and Cliff Shaw. , and It was the first program deliberately engineered to perform automated reasoning and is called "the first artificial intelligence prog ...
(1956), the
General Problem Solver General Problem Solver (GPS) is a computer program created in 1959 by Herbert A. Simon, J. C. Shaw, and Allen Newell (RAND Corporation) intended to work as a universal problem solver machine. In contrast to the former Logic Theorist project, the GP ...
(1957), and their
computer chess Computer chess includes both hardware (dedicated computers) and software capable of playing chess. Computer chess provides opportunities for players to practice even in the absence of human opponents, and also provides opportunities for analysi ...
program NSS (1958). Several versions of IPL were created: IPL-I (never implemented), IPL-II (1957 for
JOHNNIAC The JOHNNIAC was an early computer built by the RAND Corporation (not Remington Rand, maker of the contemporaneous UNIVAC I computer) and based on the von Neumann architecture that had been pioneered on the IAS machine. It was named in honor of ...
), IPL-III (existed briefly), IPL-IV, IPL-V (1958, for
IBM 650 The IBM 650 Magnetic Drum Data-Processing Machine is an early digital computer produced by IBM in the mid-1950s. It was the first mass produced computer in the world. Almost 2,000 systems were produced, the last in 1962, and it was the first ...
,
IBM 704 The IBM 704 is a large digital mainframe computer introduced by IBM in 1954. It was the first mass-produced computer with hardware for floating-point arithmetic. The IBM 704 ''Manual of operation'' states: The type 704 Electronic Data-Pro ...
,
IBM 7090 The IBM 7090 is a second-generation transistorized version of the earlier IBM 709 vacuum tube mainframe computer that was designed for "large-scale scientific and technological applications". The 7090 is the fourth member of the IBM 700/7000 se ...
,
Philco model 212 Philco (an acronym for Philadelphia Battery Company) is an American electronics manufacturer headquartered in Philadelphia. Philco was a pioneer in battery, radio, and television production. In 1961, the company was purchased by Ford and, from 196 ...
, many others. Widely used), IPL-VI. However the language was soon displaced by
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 ...
, which had much more powerful features, a simpler syntax, and the benefit of automatic
garbage collection Waste collection is a part of the process of waste management. It is the transfer of solid waste from the point of use and disposal to the point of treatment or landfill. Waste collection also includes the curbside collection of recyclabl ...
.


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''—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 LispJohn 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.


References


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. * Newell, Allen, and Fred M. Tonge. 1960. "An Introduction to Information Processing Language V." CACM 3(4): 205-211. * Newell, Allen. 1964. ''Information Processing Language-V Manual; Second Edition''. Rand Corporation llen Newell Englewood Cliffs, NJ: Prentice-Hall. * Samuel, Arthur L.: Programming Computers to Play Games. In: Advances in Computers, Vol. 1, 1960, pp 165–192 (esp.: 171-175).


External links


Allen Newell, "Biographical Memoirs", National Academy of Sciences (includes a short section on IPL)

IPL documents from BitSavers


{{Authority control Procedural programming languages History of artificial intelligence Programming languages created in 1956