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From: ForthNet@willett.pgh.pa.us (ForthNet articles from GEnie)
Newsgroups: comp.lang.forth
Subject: Input/Output
Message-ID: <2942.UUL1.3#5129@willett.pgh.pa.us>
Date: 30 Jun 91 20:12:02 GMT
Organization: (n.) to be organized.  But that's not important right now.
Lines: 30

Category 10,  Topic 23
Message 11        Sat Jun 29, 1991
L.ZETTEL                     at 21:25 EDT
 
This is one committee member's private, unofficial assesment of  where BASIS17
stands with regard to the material in message 8:

BCD has been specifically disallowed.  The relevant section of  5.3.1 now
reads:

" This standard allows one's complement, two's complement, or  sign-magnitude
representations.  In these systems arithmetic zero  is represented as the
value of a single cell with all bits clear.  This  enumeration of allowed
number representations specifies a  correspondence between numbers and bit
masks."

And that is why it was done.  The problem is that in twos  complement the
binary representation of ten is  ... 0000 1010 .  In  BCD it is (I believe) 
... 0001 0000 .  There is NO WAY the  customary hacks for constructing masks
with arithmetic could work  the same way in both systems.  They _will_ work in
one's  complement as long as the sign bit is not set (i. e., arithmetic is 
done on positive values only).  Nobody seems to be sure about  signed-
magnitude, but that is looked on as pretty much only of  academic interest.
                                         -LenZ-

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