> Back in the olde daze, (not sure whether it is still true), loading a > register from an address not aligned would cause an abend, or poor > performance.
The change came with the byte oriented operand feature of the 360/85, and only applied to unprivileged instructions. If your code depended onnn getting a program interrupt with an IC of 6 then you had to rewrite it; there was no way to turn the feature off. AFAIK there is still a performance penalty, and there is also the issue of software that imposes its own alignment requirements. -- Shmuel (Seymour J.) Metz http://mason.gmu.edu/~smetz3 ________________________________________ From: IBM Mainframe Discussion List [IBM-MAIN@LISTSERV.UA.EDU] on behalf of Rupert Reynolds [rreyno...@cix.co.uk] Sent: Saturday, July 4, 2020 5:34 PM To: IBM-MAIN@LISTSERV.UA.EDU Subject: Re: Assembler question The question on my mind is "What did you want to achieve?" If you wanted an aligned fullword for OW0007AC then you need to decide whether to align REPORT07 2 bytes after a fullword boundary (precede it with CNOP 2,4 from memory) or whether you want slack bytes in the record. Back in the olde daze, (not sure whether it is still true), loading a register from an address not aligned would cause an abend, or poor performance. Rupert On Sat., Jul. 4, 2020, 21:27 Joe Monk, <joemon...@gmail.com> wrote: > So in REPORT07, you have: 0CL274. This will not reserve any storage, > because the multiplier is zero. (7FE). > > In the next variable, you have XL2. This is hex, length 2. Notice the > location counter is at exactly the same place at REPORT07. (7FE). > > In the next variable you have XL2 again. This is hex, length 2. Notice the > location counter has now increased by 2 (800). > > In the next variable, you have a Fullword. A fullword cannot start on a > halfword boundary (802), so the assembler bumps the location counter to the > next fullword (804). > > Same thing for your next two variables. > > Joe > > On Sat, Jul 4, 2020 at 2:48 PM Nguyen Dt <ndt....@gmail.com> wrote: > > > Dear lister, > > I am learning assembler on my own, i have something strange that i can't > > explain , please help me to understand > > > > Here is a section of my code : > > > > 608 DBLWORD DS D DBLE WORD > > > > 609 PATTERN6 DC X'402020202120' > > 610 * > > > > 611 REPORTO7 DS 0CL274 > > > > 612 OW0007DB DS XL2 > > > > 613 OW0007OB DS XL2 > > > > 614 OW0007AC DS F > > > > 615 OW0007NP DS H > > > > 616 OW0007PT DS F > > > > 617 OW0007PF DS CL256 > > > > 618 * > > > > > > > > And here is the listing at compilation > > > > 0007FE 611 REPORTO7 DS 0CL274 > > > > 0007FE 612 OW0007DB DS XL2 > > > > 000800 613 OW0007OB DS XL2 > > > > 000804 614 OW0007AC DS F > > > > 000808 615 OW0007NP DS H > > > > 00080C 616 OW0007PT DS F > > > > > > > > I don't undestand why OW0007OB is 2 bytes , but on the left it is > > considered as 4 bytes long , the same for QW0007NP > > I read something with alignment obut it seems to concern constants , and > > this is not constant ? > > > > > > Thank you for clarification > > > > > > ---------------------------------------------------------------------- > > For IBM-MAIN subscribe / signoff / archive access instructions, > > send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN > > > > ---------------------------------------------------------------------- > For IBM-MAIN subscribe / signoff / archive access instructions, > send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN > ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
