Converting AT&T Troff Documents to Markdown: Classical Unix Typesetting

In 1973, Joe Ossanna at AT&T Bell Laboratories created troff ("typesetter roff") to drive a Graphic Systems CAT phototypesetter connected to a PDP-11 Unix computer. Later enhanced by Brian Kernighan into device-independent troff (ditroff) in 1979, the system became the bedrock of computer science documentation.

From classical Bell Labs Technical Memoranda to the original manuscripts of Brian Kernighan and Dennis Ritchie's The C Programming Language, troff documents (.tr, .troff, .t) contain decades of foundational computing research.

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1. Classical Troff Requests vs Modern Markdown

Troff processes text using a stream of imperative dot requests and inline escapes:

• Three-Part Titles (.tl): Formats left, center, and right header/footer content: .tl 'Draft'The C Language'1978'.
• Vertical and Horizontal Spacing (.sp, .br, .bp): Controls baseline advances, paragraph breaks, and page boundaries.
• Centering and Indents (.ce, .in, .ti): Sets running margin indents and centered display blocks.
• Preformatted Verbatim (.nf / .fi): Disables line filling to preserve source code listings and ASCII diagrams.
• String Registers (.ds / \*(name): Defines reusable textual macros and variable expansions.
• Classical Macro Packages (ms, me, mm): Provides high-level abstractions like .TL (title), .AU (author), .NH (numbered heading), .PP (paragraph), and .QP (quoted block).

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2. Transforming Troff Primitives into Clean GFM

convrtr parses troff requests and string registers directly in the browser:

1. Heading Synthesis: Maps .TL to # Document Title, .NH 1 to ## Primary Section, and .NH 2 to ### Subsection.
2. Typography Escapes: Resolves inline character escapes (\fB bold, \fI italic, \f(CW monospace, \(em em-dash) into clean GitHub Flavored Markdown.
3. Blockquotes and Code Blocks: Maps .QP to Markdown blockquotes (>) and .nf/.fi blocks to fenced code blocks.
4. Macro Stripping: Cleanly ignores raw typesetting driver requests while preserving content flow.

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3. Fast, Private In-Browser Document Processing

Technical reports, internal research papers, and archived Unix manuscripts should remain private. convrtr processes AT&T troff files 100% client-side in your browser with zero network requests.