Telefunken TR4 and TR440, which had two tag bits for each 48 bit word of storage. The bits where represented in the registers, too.
The meaning was 0 - binary floating point 1 - binary fixed point 2 - instructions 3 - other, like decimal or char Some instructions, like Load (in German: B = Bringe) worked different for fixed point and floating point, for example. If you tried to do a binary fixed arithmetic instruction on a word with tag (Typenkennung) = 2 or 3, a special kind of ABEND occured (Typenkennungs-Alarm). So it was good practice to initialize all dynamic storage with Typenkennung = 2 or 3. But you could modify machine instructions as in every other architecture, but only with the correct instructions. Modification was normally not done in storage, but when fetching the instruction, a modificator value from the previous instructions was (optionally) added. And there was even an instruction like EX on 360 to execute instructions at arbitrary places in storage, and these instruction also were allowed to have Typenkennung 0 or 1. Instructions normally were placed in read-only storage. Kind regards Bernd Am Sonntag, 10. September 2006 14:09 schrieben Sie: > On 9 Sep 2006 22:02:52 -0700, in bit.listserv.ibm-main you wrote: > >In <[EMAIL PROTECTED]>, on 09/08/2006 > > > > at 06:11 PM, Bernd Oppolzer <[EMAIL PROTECTED]> said: > >>BTW, on older machines (not IBM) there were concepts like storage > >>tags, which allowed to detect the use of uninitialized variables > >>even for binary values. I don't understand why these concepts never > >>reached the market. > > > >They did: Burroughs, now part of Unisys. RCA. Probably others as well. > > What models and was it other than just data and instruction? ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
