On Oct 29, 2008, at 16:32, Mike Walter wrote:
That X2D conversion works "as expected" in rexx. E.g. FFFF = 65535 But with SPECS X2D, FFFF = -127 Obviously, it's respecting the high order bit. High astonishment factor.
FSVO "respecting". There are cultural norms that ought to be paid greater respect: o We come from a background of 2's complement hardware. In 2's complement, FFFF = -1 is a plausible conversion. FFFF = -127 is not. o We come from a background of Rexx. The Rexx convention, FFFF = 65535 is plausible. FFFF = -127 is not. o I haven't checked the doc. If X2D is limited to 2 hex digits, the processor ought to have reported an error on a 4-digit value. Apparently the processor takes the high-order bit as a sign and 7 other bits (but which 7?) as a magnitude. Sign-magnitude representation is traditional elswhere, but not among descendants of the IBM 360. Rationale? -- gil
