Edward Jaffe is correct. In general, for arbitrary multiple-precision arithmetic, do no with-borrow on the lowEST-order element and do with-borrow on the highER-order elements There is a lucid, very full discussion of multiple-precision arithmetic in Donald Knuth, The art of computer programming, volume 2, seminumerical algorithms [any edition, including the cheap European paperback one if you can find it].
Numbering the BYTES of an STCKE value in zero-origin fashion from left to right, bytes 14 and 15 contain the programmable-field value. Do not include it in your calculations. Do include byte 0; after 23:58:43 on 2042 September 17 you will need it. On 1/9/12, Edward Jaffe <[email protected]> wrote: > On 1/9/2012 1:40 PM, Steve Comstock wrote: >> Here's what I'm thinking: >> >> LMG R2,R4,datetimen - put datetime into R2/R3 >> (use 64 bits in each reg) >> and put datetimes into R4/R5 >> (use 64 bits in each reg) >> SLBGR R3,R5 >> SLBGR R2,R4 > > You're not supposed to use a logical subtract 'with borrow' on the low-order > part. You use it only on the high-order part--AFTER doing a logical subtract > 'without borrow' on the low-order part. > > -- > Edward E Jaffe > Phoenix Software International, Inc > 831 Parkview Drive North > El Segundo, CA 90245 > 310-338-0400 x318 > [email protected] > http://www.phoenixsoftware.com/ > -- John Gilmore, Ashland, MA 01721 - USA
