Re: how to create unsigned hexadecimal initial value

[rjd@xxxxxxxxxx]

On 08/24/2000 at 12:32:29 AM, "Peter Dow" <pdow@earthlink.net> wrote:

     What's the difference between H"80000000" in Gene's initial post and
X'80000000' that everyone else used? Is there some significance to using H
and " instead of X and '? Are they supposed to be equivalent?


H'80000000' is a numeric literal.  More specifically, it has the attributes
of a signed integer.

X'80000000' is a character literal.  It has the attributes of a character
type.

Given the following declaration of FLAG,

  DCL DD FLAG AUTO BIN(4) UNSGND;

we've observed several behaviors which can be explained in terms of the
integer vs character attributes of the literal values:

DCL DD FLAG AUTO BIN(4) UNSGND INIT(H"80000000");
  -- fails at compile time because the assembler recognizes that the
initial value is negative (recall that H-literals are signed).

DCL DD FLAG BIN(4) UNSGND AUTO INIT(X'80000000');
  -- works because the initialization of automatic data is implemented
using "copy bytes"-like instructions, which ignore numeric atrributes of
the data.

CPYNV FLAG, H"80000000";
  -- fails at runtime with binary overflow (mch1210).  The exception occurs
when the signed integer value (-2147483648) is converted to unsigned in
preparation for the store to FLAG.

CPYNV FLAG, X'80000000';
  -- fails at compile time because operand 2 has character attributes
instead of numeric attributes

CPYBLA FLAG, X'80000000';
  -- works because CPYBLA ignores the numeric attributes of the receiver

CPYNV FLAG, 2147483648;
  -- works because an unsigned literal is specified

DCL DD FLAG AUTO BIN(4) UNSGND INIT(2147483648);
  -- works because an unsigned literal is specified


Bob Donovan
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