Alec Nevala-Lee

Thoughts on art, creativity, and the writing life.

Joe Armstrong’s Law of Debugging

with one comment

Joe Armstrong

Then there’s—I don’t know if I read it somewhere or if I invented it myself—Joe’s Law of Debugging, which is that all errors will be plus/minus three statements of the place where you last changed the program. When I worked at the Swedish Space Corporation my boss was a hardware guy. We were up at Esrange, the rocket-launching site and satellite-tracking station in the north. And one time he was banging his head, debugging some bug in the hardware, plugging in oscilloscopes, and changing things. And I said, “Oh, can I help?” And he said, “No Joe, you can’t help here—this is hardware.” And I said, “Yeah, but it must be like software—the bug will be pretty near the last change you made to the hardware.” And he went, “I changed a capacitor. You’re a genius!” He’d replaced one capacitor with a bigger capacitor and he unsoldered it and put the original one back and it worked. It’s the same everywhere. You fix your car and it goes wrong—it’s the last thing you did. You changed something—you just have to remember what it was. It’s true with everything.

—Joe Armstrong, developer of Erlang, in Coders at Work by Peter Seibel

Written by nevalalee

September 14, 2013 at 9:50 am

One Response

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  1. Reblogged this on sooyookang28 and commented:
    MY LIKE

    sooyookang28

    September 16, 2013 at 8:29 pm


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