My increasingly failure-prone long-term memory thought that I had heard or read somewhere long ago that this was true. Upon Googling, I have found this discussion of PDP's vs. IBM's bit numbering schemes: http://onlamp.com/pub/a/onlamp/2007/02/22/open-formats-open-source.html
I may have heard this story long ago and conflated "PDP's engineers" with "all hardware engineers everywhere." I regret my earlier comments on this topic. But reading about the little- and big-endian ways of numbering bits is very interesting. Bill Fairchild Programmer Rocket Software 408 Chamberlain Park Lane • Franklin, TN 37069-2526 • USA t: +1.617.614.4503 • e: [email protected] • w: www.rocketsoftware.com -----Original Message----- From: IBM Mainframe Discussion List [mailto:[email protected]] On Behalf Of Tom Marchant Sent: Wednesday, September 19, 2012 11:22 AM To: [email protected] Subject: Re: Is there a correspondence between 64-bit IBM mainframes and PoOps editions levels? On Wed, 19 Sep 2012 14:25:11 +0000, Bill Fairchild wrote: >It could be a lot worse. Hardware engineers number the bits in a byte >in the opposite manner that we software techies do; i.e., bit 0 >(hardware) = bit 7 (software), etc. Do they really? I know that the documentation for some architectures have the bits numbered with 0 being the low-order bit. Programmers working on those architectures typically number the bits the same way. AFAICT, everything to do with IBM mainframes has bit 0 as the high-order bit. I know that this was true of the Amdahl engineering documents. -- Tom Marchant ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
