My professor made this claim... 
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 My professor made this claim...




Sat, 12 May 2001 03:00:00 GMT  
 My professor made this claim...
I'm missing something here... Last time I checked, X'30' was the printable ASCII

Quote:


> > A-I are C1-C9 in EBCDIC because they are punched as 12-1 through 12-9.

> I would like to add a minor point, which is probably clear to most readers, but
> for folks like me it takes a little study to see the point.

> The derrivation of the EBCDIC encodings from Hollerith card encodings, explains
> not only the assignments of values, but it explains the gaps in the alphabetic
> sequence.

> The Hollerith cards are primitive, if we consider hexadecimal orthogonality as
> the indicator of modernism.  The 80-column Hollerith code table reflects the
> physical reality of the adding machines that the tabulating machinery was
> intended to replace.

> The very best example I ever saw of this phenomena was a ceramic vase from
> ancient Geeece that was formed in a shape and surfase that mimicked the older
> bronze vases with dummy fittings (almost like nuts and bolts) around the top
> rim. Maybe people trusted this more, or were comforted by the familiarity.

> The Hollerith codes for the numerics are exact analogs to the key selections of
> an old adding machine that had columns and rows of numbers
> The analog is exact.

> The alphabetics are an extension of this symetric table. On the quasi decimal
> cards (not on the binary machines), the C-9 is followed by D-1. On an adding
> machine with columns of numbers it is not necessary to punch zero (not even
> intermediate zero); because the function of zero as a place holder is not
> needed in hardware where the place is fixed spatially. And although D9 would
> seem to follow E1, it is worth noting that Z being at the bottom reflects a
> table that was built from the bottom of the row/column matrix of quasi-decimal
> values. It is as though it was a big adding machine style typewriter. The
> 'lower keys' would be easier to get to, so stack an incomplete column from the
> bottom (comparable to a 'pop- up' menu as opposed to a 'pull-down' menu).

> The Hollerith cards and machinery were used to compile a U.S. census that was
> running very late managed by only traditional methods. The method used replaced
> adding machines that are just about depicted in the code set.

> Although ASCI breaks free of the syncopated encoding partly, it is not free of
> artifacts from the past.  The numerics start at x'31', not at x'30', and are
> followed by special character filler, so that the alphabetics start in the next
> column. And the cipher-A is not x'40' but is x'41'. The alphas could have as
> easily been placed at x'40', and still been able to exploit logical operations
> to transform to/from lower/upper case.

> To a very small extent, and in a really faint way, the placement of cipher-A at
> x'41' in _ASCII_ still echoes the non-entry of zero on fixed column arithmetic
> machinery of the 19-th century.

> Best Wishes,

> Robert Rayhawk




Sat, 12 May 2001 03:00:00 GMT  
 My professor made this claim...
My statement that the ASCII numerics start at x'31' needs correction. The
cipher zero is, of course, x'30'. But the alphaberics do not start at x'40',
they start at x'41'.


easily been placed starting at x'40' rather than x'41'.

Had the alphabetics merely been placed just after the numerics (say, starting
at x'3A'), then the capital letters would have spanned portions of two columns,
making it harder to enable logical operations to convert upper to lower case.

By starting at or near the top of the next column, the span was reduced to two
columns. So why not just start at x'40'.  My point is that there is a faint
residual artifact, that represents skipping zero, or establishing codes on a
basis of one rather than zero as the origin, Which is visible in both EBCDIC
and ASCII code assignments for the alphabetics.

In ASCII the origin of the pattern is sufficiently obscure as to be nearly
invisible. But the fact is there, hex 4-0 was skipped. (I don't mean that it
was not assigned to something, it was just skpped for the alphabetics). In
EBCDIC, the skipping is much more apparent. And on the Hollerith cards, the
layout of the punch image is directly analogous to the old row and column
adding machinery.

As you look at the ASCII code it seems like a stretch that this explanation
would be applicable. And no doubt readers of this newsgroup might feel there
are better ways to spend their reading time.  But for me the important thing to
explain about the distracting discontinuous EBCIDIC code assignments is not the
filled portion but the gaps in the alphabetics.  It is important because it
records the passing of the machinery that had the fixed position rows and
columns of numbers on the front interface.

Another interesting thing about ASCII is that the special characters that
preceed the numerics correspond in sequence to the shifted numeric keys values
of a standard typerwriter.

Atleast in part.  For the truth is that there was only a general standard. On a

instead a double quote.  And although there might have been competing keyboard
standards, there were certainly no shift-hex-A thru shift-hex-F.  So had
competing standards pushed the at sign out of the area x'20' thru x'29', there
was room left that would have allowed the at sign to occur as a cipher lower in
ordinality than cipher-A, and still not prevent cipher-A from commencing the
alphabetics at position x'40'.

So anyway, the ASCII asignment of the special characters does record a sequence
that is similar to popular typewriters of the time (the shifted numerics).  

The EBCDIC assignment of those special characters is not at all like the
typewriter.  It also has gaps (the special cipher sequence).

The code sets are records of the machines of the times.  It is also possible
that the difference in the EBCDIC and ASCII assignments reflect the historical
fact of the obtaining of the QWERTY keyboard de facto standardization.  The
Hollerith codes are older, and reflect a time when other machine standards were
considered the proper orientation for sequencing the codes. When ASCII was
chiselled out, the QWERTY keyboard (with its fairly standard assignment of
shifted numerics) was considered the proper orientation.

The thing I am after here is to deal with the fact that some people think that
the EBCDIC code is somehow deficient or derrived from poor planning.  That is
not what the sequence shows. The sequence shows history. That knowledge, I
think, can improve motivation.

The graphical layout of the EBCDIC
table also informs programmers of specific opportunities. For example, in
EBCDIC, if a cipher's lower nibble is zero you can be certain that it is not
alphabetic. If the lower portion is greater than x'9', it is not alphabetic.
(That would leave elimination of 'E1' as the only thing further to determine
alphabetic or not).  

Perhaps that three step process is neither the fastest path for assembly
programs or hardware.  But the EBCDIC table is logical and refects a clear
physical reality.

The correspondence of ASCII special ciphers is clear enough to shifted
numerics.  The skipping of x'40' as the origin for the alphabetics, requires
some further explanation. I think the precedence of prior codes (Hollerith)
helps in that explanation. But the echo is faint for sure. But it looks like a
tradition of skip zero, and use a one basis.

Best  Wishes,

Robert Rayhawk



Sat, 12 May 2001 03:00:00 GMT  
 
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