Jeff Shrager's repository introduces "executable archaeology" — the practice of recovering, transcribing, and running the original historical source of early computing programs so that the surviving artifact itself, rather than a modern rewrite, can serve as experimental evidence. The main project here is an IPL-V reimplementation of Victor Yngve's 1959–61 MIT sentence generator, run under Herbert A. Simon's account on 25 June 1962, whose surviving printout preserves the program, its phrase-structure grammar, execution traces, and handwritten corrections by Simon and his daughter Katherine.
- The repository also points to separate repos reconstructing the Logic Theorist in two historically distinct forms (LT1 in IPL-I and LT5 in IPL-V) and a full CTSS/IBM 7094 reanimation of Weizenbaum's original ELIZA
- A 2026 arXiv paper by Shrager and a 2025 IEEE Annals paper by Lane et al. provide the formal background
- Six stated principles govern the work, including distinguishing original behavior from behavior introduced by the reconstruction
- The repository also points to separate repos reconstructing the Logic Theorist in two historically distinct forms (LT1 in IPL-I and LT5 in IPL-V) and a full CTSS/IBM 7094 reanimation of Weizenbaum's original ELIZA
- A 2026 arXiv paper by Shrager and a 2025 IEEE Annals paper by Lane et al. provide the formal background
- Six stated principles govern the work, including distinguishing original behavior from behavior introduced by the reconstruction
Jeff Shrager writes a comprehensive guide to Herbert Simon's 1961 Heuristic Compiler, a program that uses General Problem Solver (GPS) means-end analysis to generate IPL-V code. After being dormant for roughly 65 years, the archival card deck was transcribed and successfully run on a modern Common Lisp interpreter. The system is composed of three parts: a State Description Compiler that derives code from before-and-after memory states, a Functional Description Compiler that modifies existing code based on imperative phrases, and a General Compiler executive that manages the search process. Notably, the program reproduces the exact machine code printed in Simon's 1963 paper, such as the "INSERT AT END OF VALUE LIST" and "SET SIGNAL MINUS" examples, without any modern language rewrites.
- The guide highlights that the compiler treats routine generation as a problem to be solved via operator search rather than a direct translation task.
- A debugging print statement left in routine U113 happens to output the exact stage-by-stage compilation sequence described in the 1963 paper.
- The original 1961 deck fails to compile the J3 routine; a specific card must be modified to erase a redundant description before the state compiler can execute successfully.
- The guide highlights that the compiler treats routine generation as a problem to be solved via operator search rather than a direct translation task.
- A debugging print statement left in routine U113 happens to output the exact stage-by-stage compilation sequence described in the 1963 paper.
- The original 1961 deck fails to compile the J3 routine; a specific card must be modified to erase a redundant description before the state compiler can execute successfully.
This repository provides an implementation and recreation of the first published version of the Logic Theory Machine, also known as the Logic Theorist. Originally developed by Allen Newell, J. C. Shaw, and Herbert A. Simon in 1956, this program was designed to prove theorems in propositional logic using principles from Principia Mathematica. The project includes a Python-based interpreter for the IPL-I abstract machine language, tools to run the program against historical axioms and theorems, and utilities to analyze generated proofs.
Main components:
Implementation of the 1956 Logic Theory Machine
Propositional logic based on Principia Mathematica
Python interpreter for the IPL-I language
Tools for running simulations and verifying results
Main components:
Implementation of the 1956 Logic Theory Machine
Propositional logic based on Principia Mathematica
Python interpreter for the IPL-I language
Tools for running simulations and verifying results
https://gordonbell.azurewebsites.net/Computer_Structures__Readings_and_Examples/contents.html
Proc. WJCC, pp. 119-128, 1958.
Chapter 30
A command structure for complex information processing1
J. C. Shaw / A. Newell / H. A. Simon / T. O. Ellis
The general-purpose digital computer, by virtue of its large capacity and general-purpose nature, has opened the possibility of research into the nature of complex mechanisms per se. The challenge is obvious: humans carry out information processing of a complexity that is truly baffling. Given the urge to understand either how humans do it, or alternatively, what kinds of mechanisms might accomplish the same tasks, the computer is turned to as a basic research tool. The varieties of complex information processing will be understood when they can be synthesized: when mechanisms can be created that perform the same processes.
Proc. WJCC, pp. 119-128, 1958.
Chapter 30
A command structure for complex information processing1
J. C. Shaw / A. Newell / H. A. Simon / T. O. Ellis
The general-purpose digital computer, by virtue of its large capacity and general-purpose nature, has opened the possibility of research into the nature of complex mechanisms per se. The challenge is obvious: humans carry out information processing of a complexity that is truly baffling. Given the urge to understand either how humans do it, or alternatively, what kinds of mechanisms might accomplish the same tasks, the computer is turned to as a basic research tool. The varieties of complex information processing will be understood when they can be synthesized: when mechanisms can be created that perform the same processes.
