Re: non-ASCII environment
On Fri, 9 Apr 2010 17:57:04 -0400 (EDT), John Hasler wrote:
> Stephen Powell writes:
>> Yes, Hercules is an IBM mainframe emulator. But the problem is
>> licensing. There are some *very old* releases of IBM operating
>> systems that have passed into the public domain that you can run on
>> the Hercules emulator.
>> These are circa 1975 or so, which is about 35 years ago. An example
>> is VM/SP Release 6.
Oops! I meant to say VM/370 Release 6, not VM/SP Release 6. VM/SP
Release 6 is still proprietary.
-----
These are some of the issues that someone writing portable code
for ASCII vs. EBCDIC implementations needs to worry about.
(1) Collating sequence. In ASCII, the collating sequence is numbers
(0-9), followed by uppercase letters (A-Z), followed by lowercase
letters (a-z). Special characters are mixed throughout. In EBCDIC,
the collating sequence is lowercase letters (a-z), followed by
uppercase letters (A-Z), followed by numbers (0-9). So records
sorted alphabetically sort in a different order.
(2) Assumptions of continuity. In ASCII, the codes a-z and A-Z
are contiguous, with no codes in between. In EBCDIC, there are
six non-contiguous ranges, a-i, j-r, s-z, A-I, J-R, S-Z. Most
of the codes in between are non-printable characters, but not
all. For example, ~ sorts above r and below s, } sorts above I
and below J, and \ sorts above R and below S.
(3) Hidden assumptions about control codes. A program may, for
example, assume that X'0A' is a line feed and hard code it
somewhere. In ASCII, that is true. But in EBCDIC, a line feed
is X'25'.
(4) 7-bit assumptions. In U.S. standard ASCII, all the printable
characters are between the hex values of X'00'-X'7F'. Codes
above X'7F' are not standard codes. Historically, these indicate
the combination of the "Meta" key with a regular code. In
EBCDIC, the codes are sprinkled throughout the entire range of
X'00' through X'FF', with the numeric symbol 9 having the highest
code of any normal printable character (X'F9').
This is not an exhaustive list, but it gives you an idea
of what to watch for. Although the
following table has a few mistakes, this link will give you
an idea of ASCII vs. EBCDIC codes.
http://www.natural-innovations.com/computing/asciiebcdic.html
--
.''`. Stephen Powell <zlinuxman@wowway.com>
: :' :
`. `'`
`-
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