Turbo Pascal 3.02A, deconstructed

2026-03-20 · Source: Simon Willison's Weblog · Field: Technology & Digital — Artificial Intelligence & Machine Learning, Software Development & Engineering · Depth: Intermediate, quick

Summary

Simon Willison deconstructed Borland's 1985 Turbo Pascal 3.02A executable, a 39,731-byte file that remarkably integrated a full text editor IDE and Pascal compiler. Inspired by James Hague's 2011 article on its small size, Willison used Claude to interpret and decompile the binary, which has been available as freeware since 2000. The process involved a sequence of prompts to Claude, leading to the creation of an interactive artifact. This artifact embeds the turbo.com binary, displaying it broken into 17 labeled segments, decompiled into assembly, and then reconstructed into readable, extensively annotated code. Key statistics include 39,731 total bytes, 17 mapped segments, 1 INT 21H instruction, and over 100 built-in identifiers.

Key takeaway

For research scientists exploring legacy software or reverse engineering old systems, you should consider using advanced AI models like Claude to deconstruct and interpret binary executables. This approach can significantly accelerate the understanding of complex, compact codebases from historical software, potentially revealing architectural insights or forgotten optimization techniques without extensive manual effort.

Key insights

AI models can effectively deconstruct and interpret legacy binary executables into human-readable code.

Principles

• Small binaries can contain complex functionality.
• AI can aid reverse engineering of old software.

Method

The method involved using an AI (Claude) to analyze a binary, decompile it to assembly, and then reconstruct it into annotated, readable code, finally presenting it as an interactive artifact.

In practice

• Use AI for legacy code analysis.
• Create interactive visualizations for complex binaries.

Topics

• Large Language Models
• Binary Analysis
• Code Decompilation
• Reverse Engineering
• Legacy Software

Best for: AI Scientist, Research Scientist, AI Engineer, AI Researcher, Software Engineer

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Editorial summary, takeaway, and curation by AIssential. Original article published by Simon Willison's Weblog.