Information Processing Language
Encyclopedia
Information Processing Language (IPL) is a programming language
developed by Allen Newell
, Cliff Shaw
, and Herbert Simon
at RAND Corporation and the Carnegie Institute of Technology
from about 1956. Newell had the role of language specifier-application programmer, Shaw was the system programmer and Simon took the role of application programmer-user.
The language includes features intended to support programs that could perform general problem solving, including lists, associations, schemas (frames), dynamic memory allocation, data types, recursion, associative retrieval, functions as arguments, generators (streams), and cooperative multitasking. IPL pioneered the concept of list processing, albeit in an assembly-language style.
The main 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 called L1 holding 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
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 head 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:
which were laboriously proven by hand, by Bertrand Russell
and Alfred North Whitehead
, could in fact be proven by computation
. According to Simon's autobiography Models of My Life, this first application was 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 Theory Machine (1956), the General Problem Solver
(1957), and their computer 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
, many others. Widely used), IPL-VI.
However the language was soon displaced by Lisp
, which had far more powerful features, a simpler syntax, and the benefit of automatic garbage collection
.
Many of these features were generalized, cleaned up, and incorporated into Lisp and from there into a wide spectrum of programming languages over the next several decades.
Programming language
A programming language is an artificial language designed to communicate instructions to a machine, particularly a computer. Programming languages can be used to create programs that control the behavior of a machine and/or to express algorithms precisely....
developed by Allen Newell
Allen Newell
Allen Newell 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 of Psychology...
, Cliff Shaw
Cliff Shaw
J.C. Shaw 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 Information Processing Language, a programming language of the 1950s. It is considered the true "father" of the JOSS...
, and Herbert Simon
Herbert Simon
Herbert Alexander Simon was an American political scientist, economist, sociologist, and psychologist, and professor—most notably at Carnegie Mellon University—whose research ranged across the fields of cognitive psychology, cognitive science, computer science, public administration, economics,...
at RAND Corporation and the Carnegie Institute of Technology
Carnegie Institute of Technology
The Carnegie Institute of Technology , is the name for Carnegie Mellon University’s College of Engineering. It was first called the Carnegie Technical Schools, or Carnegie Tech, when it was founded in 1900 by Andrew Carnegie who intended to build a “first class technical school” in Pittsburgh,...
from about 1956. Newell had the role of language specifier-application programmer, Shaw was the system programmer and Simon took the role of application programmer-user.
The language includes features intended to support programs that could perform general problem solving, including lists, associations, schemas (frames), dynamic memory allocation, data types, recursion, associative retrieval, functions as arguments, generators (streams), and cooperative multitasking. IPL pioneered the concept of list processing, albeit in an assembly-language style.
A taste 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 built from several cells holding 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 main 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 called L1 holding 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-V List Structure Example
Name SYMB L1
9-1
100
S4
101
S5
9-1
0
200
A1
201
V1
202
A2
203
V2
0
IPL is an assembly language
Assembly language
An assembly language is a low-level programming language for computers, microprocessors, microcontrollers, and other programmable devices. It implements a symbolic representation of the machine codes and other constants needed to program a given CPU architecture...
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 head 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
The first application of IPL was to demonstrate that the theorems in Principia MathematicaPrincipia Mathematica
The Principia Mathematica is a three-volume work on the foundations of mathematics, written by Alfred North Whitehead and Bertrand Russell and published in 1910, 1912, and 1913...
which were laboriously proven by hand, by Bertrand Russell
Bertrand Russell
Bertrand Arthur William Russell, 3rd Earl Russell, OM, FRS was a British philosopher, logician, mathematician, historian, and social critic. At various points in his life he considered himself a liberal, a socialist, and a pacifist, but he also admitted that he had never been any of these things...
and Alfred North Whitehead
Alfred North Whitehead
Alfred North Whitehead, OM FRS was an English mathematician who became a philosopher. He wrote on algebra, logic, foundations of mathematics, philosophy of science, physics, metaphysics, and education...
, could in fact be proven by computation
Automated theorem proving
Automated theorem proving or automated deduction, currently the most well-developed subfield of automated reasoning , is the proving of mathematical theorems by a computer program.- Decidability of the problem :...
. According to Simon's autobiography Models of My Life, this first application was 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
Artificial intelligence is the intelligence of machines and the branch of computer science that aims to create it. AI textbooks define the field as "the study and design of intelligent agents" where an intelligent agent is a system that perceives its environment and takes actions that maximize its...
programs, also by the same authors: the Logic Theory Machine (1956), the General Problem Solver
General Problem Solver
General Problem Solver was a computer program created in 1959 by Herbert Simon, J.C. Shaw, and Allen Newell intended to work as a universal problem solver machine. Any formalized symbolic problem can be solved, in principle, by GPS. For instance: theorems proof, geometric problems and chess...
(1957), and their computer chess
Computer chess
Computer chess is computer architecture encompassing hardware and software capable of playing chess autonomously without human guidance. Computer chess acts as solo entertainment , as aids to chess analysis, for computer chess competitions, and as research to provide insights into human...
program NSS (1958).
Several versions of IPL were created: IPL-I (never implemented), IPL-II (1957 for JOHNNIAC
JOHNNIAC
The JOHNNIAC was an early computer built by RAND that was based on the von Neumann architecture that had been pioneered on the IAS machine. It was named in honor of von Neumann, short for John v. Neumann Numerical Integrator and Automatic Computer...
), IPL-III (existed briefly), IPL-IV, IPL-V (1958, for IBM 650
IBM 650
The IBM 650 was one of IBM’s early computers, and the world’s first mass-produced computer. It was announced in 1953, and over 2000 systems were produced between the first shipment in 1954 and its final manufacture in 1962...
, IBM 704
IBM 704
The IBM 704, the first mass-produced computer with floating point arithmetic hardware, was introduced by IBM in 1954. The 704 was significantly improved over the IBM 701 in terms of architecture as well as implementations which were not compatible with its predecessor.Changes from the 701 included...
, IBM 7090
IBM 7090
The IBM 7090 was a second-generation transistorized version of the earlier IBM 709 vacuum tube mainframe computers and was designed for "large-scale scientific and technological applications". The 7090 was the third member of the IBM 700/7000 series scientific computers. The first 7090 installation...
, many others. Widely used), IPL-VI.
However the language was soon displaced by Lisp
Lisp programming language
Lisp is a family of computer programming languages with a long history and a distinctive, fully parenthesized syntax. Originally specified in 1958, Lisp is the second-oldest high-level programming language in widespread use today; only Fortran is older...
, which had far more powerful features, a simpler syntax, and the benefit of automatic garbage collection
Garbage collection (computer science)
In computer science, garbage collection is a form of automatic memory management. The garbage collector, or just collector, attempts to reclaim garbage, or memory occupied by objects that are no longer in use by the program...
.
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 do it in a principled way.)
- Computation with symbols (except that the symbols are letter+number, not full words)
- Virtual machine
Many of these features were generalized, cleaned up, and incorporated into Lisp and from there into a wide spectrum of programming languages over the next several decades.
Publications
- 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 [Allen Newell], Englewood Cliffs, NJ: Prentice-Hall.