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From: Gordon Sande <g.sande@worldnet.att.net>
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Subject: Re: Checking for Undefined
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Date: Sat, 27 May 2006 15:10:33 GMT
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Date: 2006-05-27T15:10:33+00:00
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On 2006-05-27 11:29:31 -0300, "robin" <robin_v@bigpond.com> said:

> "Gordon Sande" <g.sande@worldnet.att.net> wrote in message
> news:2006052514574816807-gsande@worldnetattnet...
> 
>> The original WatFor for IBM/7040 used a hardware hack. They set bad parity
>> but since they were a load and go system they had a symbol table around
>> and did the lookup for you. When WatFor moved to IBM/360 the feature was so
>> popular that they had to work hard to reproduce the feature.
> 
> It wouldn't have been "hard".
> It only required the initialization of variables
> with a certain value, e.g., for integers, -2**31
> and for float, -HUGE(1.0) etc.
> (An unlikely but feasible alternative :  a bit map.)

The hardware no longer did it for free!