Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.lang.c > #6569

Re: bdiff

Show all headers | View raw

In article <00mvv69r0ignorrcegh7au2k9sbldjij26@4ax.com>,
Robert Wessel  <robertwessel2@yahoo.com> wrote:
> On 20 Jun 2011 19:14:33 GMT, blmblm@myrealbox.com
> <blmblm.myrealbox@gmail.com> wrote:
> 
> >In article <isrgpj$4qq$1@speranza.aioe.org>,
> >Alan Curry <pacman@kosh.dhis.org> wrote:
> 
> >
> >> The dinosaurs were a rowdy bunch, and they fought over how to properly store
> >> text on non-typewriter-like media (like tapes and disks), but they were all
> >> able to understand the typewriter-like ASCII-with-CRLF format. It was the
> >> universal text representation. And it was incorporated into FTP as the
> >> standard format for transmission of text files.
> >
> >I just made a quick attempt to confirm my recollections about
> >whether the IBM 360/370 architecture included support for ASCII,
> >and -- it's kind of interesting that the Wikipedia articles say
> >that the 360 architecture included some features intended to
> >support ASCII (which had not been finalized), but that these were
> >not used, or not used widely, and the 370 architecture dropped at
> >least some of them.  I wonder whether there was some consternation
> >when it became desirable to support FTP, it being ASCII-based.
> 
> 
> 
> S/360 included a mode bit that altered the behavior of a handful of
> instructions that were sensitive to the character set. This was mostly
> the decimal instructions which encoded the sign in a nibble of the
> least significant byte.  For example, in unpacked ("display") form,
> the decimal digits were 0xf0-0xf9 in EBCDIC.  Thus +123 could be
> encoded as 0xf1, 0xf2, 0xf3.  A -123 would be encoded 0xf1, xf2, 0xd3.
> (Several other values were valid for the sign as well.)  So obviously
> the instructions that converted between unpacked to packed format were
> sensitive to the character set.
> 
> In any event, it was a modest behavior change to a few instructions.
> 
> And ASCII wasn't really cooked by the time IBM started development of
> the OS's, so they ended up sticking with EBCDIC.
> 
> That mode bit was reused to enable "Extended Control" mode on the
> S/370, which instead changed to format of the PSW and a few other
> things (like some of the fixed location in low-core), that was a
> prerequisite to enabling virtual memory.  So ASCII mode went entirely
> away with the S/370.
> 
> In the last ~15 years the ISA has grown a number of instructions
> designed to ease the processing of ASCII data.  Unicode too, as well
> as instructions for converting to/from little-endian, and things like
> C-style strings.

Thanks for filling in some of the details!  That all sounds pretty
consistent with what the Wikipedia articles say, for what that's 
worth.  Interesting stuff -- though possibly more so to those of who
actually remember those days.

-- 
B. L. Massingill
ObDisclaimer:  I don't speak for my employers; they return the favor.

Back to comp.lang.c | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

variable-length strings Uno <Uno@example.invalid> - 2011-06-01 03:36 -0600
  Re: variable-length strings ccc31807 <cartercc@gmail.com> - 2011-06-01 07:13 -0700
    Re: variable-length strings Uno <Uno@example.invalid> - 2011-06-02 10:54 -0600
  Re: variable-length strings "George Mpouras" <nospam.gravitalsun@hotmail.com.nospam> - 2011-06-01 17:01 +0300
  Re: variable-length strings "Peter J. Holzer" <hjp-usenet2@hjp.at> - 2011-06-02 15:33 +0200
  Re: variable-length strings "Peter J. Holzer" <hjp-usenet2@hjp.at> - 2011-06-02 15:44 +0200
    Re: bdiff Uno <Uno@example.invalid> - 2011-06-08 21:59 -0600
      Re: bdiff Ian Collins <ian-news@hotmail.com> - 2011-06-09 16:08 +1200
        Re: bdiff Uno <Uno@example.invalid> - 2011-06-08 22:20 -0600
          Re: bdiff Uno <Uno@example.invalid> - 2011-06-09 02:57 -0600
            Re: bdiff Janis Papanagnou <janis_papanagnou@hotmail.com> - 2011-06-09 11:10 +0200
              Re: bdiff Uno <Uno@example.invalid> - 2011-06-09 13:19 -0600
                Re: bdiff James Waldby <not@valid.invalid> - 2011-06-09 19:32 +0000
                Re: bdiff Angel <angel+news@spamcop.net> - 2011-06-09 19:32 +0000
                Re: bdiff Uno <Uno@example.invalid> - 2011-06-09 15:28 -0600
                Re: bdiff blp@cs.stanford.edu (Ben Pfaff) - 2011-06-09 12:33 -0700
                Re: bdiff Uno <Uno@example.invalid> - 2011-06-09 15:15 -0600
                Re: bdiff pacman@kosh.dhis.org (Alan Curry) - 2011-06-09 22:17 +0000
                Re: bdiff blmblm@myrealbox.com <blmblm.myrealbox@gmail.com> - 2011-06-20 19:14 +0000
                Re: bdiff Robert Wessel <robertwessel2@yahoo.com> - 2011-06-20 18:43 -0500
                Re: bdiff blmblm@myrealbox.com <blmblm.myrealbox@gmail.com> - 2011-06-21 20:39 +0000
                Re: bdiff Joe Wright <joewwright@comcast.net> - 2011-06-21 18:38 -0400
                Re: bdiff Robert Wessel <robertwessel2@yahoo.com> - 2011-06-21 18:11 -0500
                Re: bdiff Michael Press <rubrum@pacbell.net> - 2011-06-22 15:51 -0700
                Re: bdiff Stephen Sprunk <stephen@sprunk.org> - 2011-06-21 07:49 -0500
                Re: bdiff blmblm@myrealbox.com <blmblm.myrealbox@gmail.com> - 2011-06-21 20:40 +0000
                Re: bdiff superpollo <superpollo@tznvy.pbz> - 2011-06-22 09:59 +0200
                Re: bdiff blmblm@myrealbox.com <blmblm.myrealbox@gmail.com> - 2011-06-22 19:57 +0000
                Re: bdiff superpollo <superpollo@tznvy.pbz> - 2011-06-23 21:16 +0200
                Re: bdiff blmblm@myrealbox.com <blmblm.myrealbox@gmail.com> - 2011-06-24 19:36 +0000
                Re: bdiff superpollo <superpollo@tznvy.pbz> - 2011-06-24 22:48 +0200
                Re: bdiff blmblm@myrealbox.com <blmblm.myrealbox@gmail.com> - 2011-06-24 21:17 +0000
                Re: bdiff Robert Wessel <robertwessel2@yahoo.com> - 2011-06-24 17:20 -0500
                Re: bdiff blmblm@myrealbox.com <blmblm.myrealbox@gmail.com> - 2011-06-22 19:55 +0000
                Re: bdiff Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-06-21 21:40 -0400
                Re: bdiff Azazel <azazel@remove.azazel.net> - 2011-06-22 09:06 -0500
                Re: bdiff Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-06-22 16:47 +0100
                Re: bdiff Stephen Sprunk <stephen@sprunk.org> - 2011-06-22 11:23 -0500
                Re: bdiff Ike Naar <ike@sverige.freeshell.org> - 2011-06-09 21:37 +0000
            Re: bdiff bonomi@host122.r-bonomi.com (Robert Bonomi) - 2011-06-19 06:10 -0500
      Re: bdiff Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-06-09 07:13 -0400
        Re: bdiff Uno <Uno@example.invalid> - 2011-06-09 13:30 -0600
          Re: bdiff Keith Thompson <kst-u@mib.org> - 2011-06-09 13:29 -0700
            Re: bdiff Uno <merrilljensen@q.com> - 2011-06-09 21:11 -0700
              Re: bdiff "Morris Keesan" <mkeesan@post.harvard.edu> - 2011-06-09 23:58 -0400
                Re: bdiff Uno <Uno@example.invalid> - 2011-06-12 00:47 -0600
                Re: bdiff Angel <angel+news@spamcop.net> - 2011-06-12 07:53 +0000
                Re: bdiff Shao Miller <sha0.miller@gmail.com> - 2011-06-12 12:02 -0500
                Re: bdiff Keith Thompson <kst-u@mib.org> - 2011-06-12 01:24 -0700
                Re: bdiff Shao Miller <sha0.miller@gmail.com> - 2011-06-12 12:18 -0500

csiph-web