Thanks for the tips! -----Original Message----- From: IBM Mainframe Assembler List <ASSEMBLER-LIST@LISTSERV.UGA.EDU> On Behalf Of Charles Mills Sent: Thursday, March 30, 2023 9:45 AM To: ASSEMBLER-LIST@LISTSERV.UGA.EDU Subject: Re: [EXTERNAL] Re: alternative to USAGE statement?
And you need to be careful to code AH 12,AFLENG-DFHAFCB(,12) Note comma And not AH 12,AFLENG-DFHAFCB(12) Note missing comma The first uses R12 as a base register; the second uses R12 as an index register off of a base of 0. They will execute and produce the same results in *most* cases with two caveats: 1. In the old days using an index register slowed things down by a cycle or so. I don't know in the brave new world of pipelines. 2. If you are in Access Register mode -- and you probably are not -- they will likely produce different results, because the former uses AR12 and the latter does not. The comma is critical in storage-storage instructions: CLC 0(12),=C'FOO' Does not do what it appears to do at all. It compares 12 bytes starting at absolute address 0 to 'FOO' plus 9 unspecified bytes. (Note the thread here about inadvertent references to low "core.") CLC MYDSECTFIELD,=C'FOO' does not have that pitfall. Charles -----Original Message----- From: IBM Mainframe Assembler List [mailto:ASSEMBLER-LIST@LISTSERV.UGA.EDU] On Behalf Of Swarbrick, Frank Sent: Thursday, March 30, 2023 12:37 AM To: ASSEMBLER-LIST@LISTSERV.UGA.EDU Subject: Re: [EXTERNAL] Re: alternative to USAGE statement? Well, the version without USING (not USAGE, of course), was not obvious at all to me until a few days ago, after 20 years of seeing it and not understanding it... Now that I understand it, though, I do find it quite readable. And I think I agree with your personal rule. The information contained in this electronic communication and any document attached hereto or transmitted herewith is confidential and intended for the exclusive use of the individual or entity named above. If the reader of this message is not the intended recipient or the employee or agent responsible for delivering it to the intended recipient, you are hereby notified that any examination, use, dissemination, distribution or copying of this communication or any part thereof is strictly prohibited. If you have received this communication in error, please immediately notify the sender by reply e-mail and destroy this communication. Thank you.
