APL Campfire

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The APL Campfire is a recurring meeting hosted by Adám Brudzewsky every fourth Sunday at 18:00 UTC, since 9 May, 2021, with each session lasting about an hour. The event focuses on the history of APL programming, inviting participants to tell stories of their experiences, and is recorded for future reference.[1]

APL Campfires are held using Zoom:


The series started after Joel Wittenberg contacted Dyalog Ltd., wanting to reconnect with the APL community. He started the APL Dinosaurs Facebook group, and suggested a live meeting. Via Zoom, he met with his friend Harry Saal and Dyalog employee Adám Brudzewsky for an hour on May 9, 2021. The meeting was deemed so enjoyable, that the group decided to make it a scheduled recurring event.


Date Speakers Subjects discussed Recording
May 9 Harry Saal, Joel Wittenberg, Adám Brudzewsky APL on mainframes, ⎕FMT's G,[2] and more
Jun 6 Joel Wittenberg, Ron Murray Murray's history with APL, including APL/700 and the APL Machine, and at Microsoft. Wittenberg's early exposure to Iverson Notation and PAT. 1:06:28
Jul 4 Len Shustek, Joey Tuttle, Joel Wittenberg Shustek at IBM, Standord, SLAC, making APL\360 a multi-user system, running it under other OSs, MFT & (Experimental) MVT, the Computer History Museum, APL.SV, Phil S. Abrams 1:06:24
Aug 1 Gitte Christensen[3], Joey Tuttle, Joel Wittenberg Working at IPSA, Ian Sharp, 666 BOX (early email), MagicStore, meeting people online (including Morten Kromberg), Christensen's first APL application, APL conferences, the boxed/nested split, Ken Iverson's Rationalized APL and J, the Rank operator, IBM/Insight Systems/Adaytum/Cognos/Dyadic Systems/Dyalog Ltd., Alex Morrow 1:06:22
Aug 29 Ray Polivka[4], Jon McGrew, Joey Tuttle, Walter Fil, Joel Wittenberg ILLIAC, at IBM, Fred Brooks, Adin Falkoff, APL\360, IBM 7030 Stretch, IVSYS/7090, Ken Iverson, Science Research Associates, computer assisted instruction, IBM 1500, teaching APL, books (own and others'), SIGAPL, SHARE, APL conferences, Iverson Award, Garth Foster, APL Quote Quad, Minnowbrook, upcoming fourth book, APL 5100, )MSG, MCM/70 1:47:56
Sep 26 Andy Shiers[5] and Geoff Streeter 40 years of Dyalog APL, early days of Dyadic Systems 1:05:42
Oct 24 Jim Brown, Ron Murray Early days at IBM and Syracuse University. Discussions with Ken Iverson and Adin Falkoff, extending base value () and represent () to work on higher rank arrays. Ragged arrays vs nested arrays. ⎕AX as prototyping too; to switch axiom system for enclosing a scalar. Origin of foo as a placeholder name in programming. Resistance to APL at IBM. Interesting internal applications at IBM: a stock application (still in use today) and QMF (Query Management Facility). Using APL for models of primitives and extensions. Behaviour of outer product (∘.), strand notation, prototypes for each on empty arrays, system labels. NARS2000's ball arithmetic. Differences in floating point results of APL vs PL/I implementations of IBM's internal planning system. The meaning of monadic Up Arrow () and Right Shoe (). Influence from Lisp (first as and "last" as ), symbols, Mike Jenkins's Matrix Inverse and Matrix Divide (), Disjoined arrays using a dedicated Disjoined Array Computer (DAC), hardware APL machines/processors, shared variables. 1:26:13
Nov 21 TBD TBD


  1. YouTube playlist
  2. "Joel Wittenberg made critical assessments of that design and suggested important elaborations which were incorporated in later designs." Adin Falkoff: A pictorial format function for patterning decorated numeric displays. APL81.
  3. 2016 Iverson Award winner.
  4. 1990 Iverson Award winner and co-author of three authoritative APL textbooks.
  5. At Dyadic Systems since 1987, now Dyalog's Chief of Operations.

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