Category Archives: Software I’ve written

HP-41 card reader bug

Posted on July 25, 2011 by Eric

It occurred to me while studying simulator traces that it might be interesting to investigate a bug in early versions of the 82104A card reader for the HP-41C calculator. The bug was fairly esoteric and easily avoided, as it seemed … Continue reading →

Posted in Calculators, Nonpareil, RetroChallenge | 2 Comments

HP-41CV ROM set version HFF bug fix

Posted on July 25, 2011 by Eric

As I was studying HP-41CV microcode running in simulation, I finally uncovered what one of the bug fixes in the HFF ROM version does. This has been a mystery for many years, though there’s still one more unexplained change relative … Continue reading →

Posted in Calculators, Nonpareil, RetroChallenge | Leave a comment

Nonpareil status

Posted on June 11, 2008 by Eric

I’m still making progress towards a new release on Nonpareil.  Sometimes it seems like the more work I do, the more I find that needs to be done.

Posted in Calculators, Nonpareil | 8 Comments

Suboptimal new computer experience — privacy vs. Mac OS X

Posted on April 10, 2008 by Eric

I just got a refurbished Apple Mac mini, with the 1.83 GHz Intel Core 2 Duo processor. It is mainly intended for use compiling my open source programs such as Nonpareil for Mac OS X. I am extremely surprised at … Continue reading →

Posted in Mac OS X, Nonpareil, Privacy, The Suboptimal Way | 4 Comments

Turing Machine in Bare Bones

Posted on March 3, 2008 by Eric

The most recent release of my Bare Bones interpreter made identifiers case-insensitive, and added an optional peephole optimizer that recognizes a common idiom: while N not 0 do;   decr N;   incr X; end; Such a loop adds N … Continue reading →

Posted in Bare Bones, Computer Science | 3 Comments

Bare Bones interpreter

Posted on February 11, 2008 by Eric

Over the weekend I finished the homework assignment for the “Theory of Computation” chapter of Computer Science: An Overview, Ninth Edition, by J. Glenn Brookshear. Brookshear defines a very minimal programming language called Bare Bones, in which variables may contain … Continue reading →

Posted in Bare Bones, Computer Science | Leave a comment

lcdtest now uses SCons instead of make

Posted on May 23, 2007 by Eric

A few people reported problems caused by the “.d” dependency files created by the dependency analysis hack in the Makefile, so I’ve updated lcdtest to use SCons instead of make.  I’ve also now made RPMs for Fedora Core 6 available … Continue reading →

Posted in Fedora, lcdtest | Leave a comment

Closed caption decoder enhancements contributed by user

Posted on May 21, 2007 by Eric

Kevin Timmerman sent me email about having built a USB version of the closed-caption decoder that Richard Ottosen and I developed.  He used an FTDI TTL-232R cable which incorporates a USB-to-serial interface chip.  He has added many new features to … Continue reading →

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lcdtest 1.04

Posted on May 7, 2007 by Eric

lcdtest wasn’t working properly with German keyboard layouts.  It was using keysyms from SDL key events, and those only indicate what the unshifted key legend is.  The fix was to enable the optional SDL key event Unicode mapping, and switch … Continue reading →

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Nonpareil status

Posted on December 9, 2006 by Eric

Several people have inquired about the status of Nonpareil, so it’s time for an update. There are major changes in progress that are mostly “under the hood.” The released versions of Nonpareil install KML, image, and ROM files in a … Continue reading →

Posted in Calculators, Nonpareil | 1 Comment