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Subject: Re: Checking for Undefined
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Date: 2006-05-27T14:29:31+00:00
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"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.)