When you enter a program, R15 points to the first byte of PROGNAME. You usually have a USING R15,PROGNAME. If you are going to be calling OS functions or programs, you will copy R15 to another register (often R12), issue a USING R12,PROGNAME and DROP R15,PROGNAME. So when using a label within 4K of PROGNAME, the assembler will use the USING register, and compute the offset from PROGNAME.
On Sun, Sep 18, 2022 at 8:12 AM Bob Bridges <robhbrid...@gmail.com> wrote: > > Twenty years ago I wrote a few programs for Excel, and didn't see what all > the fuss was about: "object-oriented" didn't seem very different from > traditional programming that I'd been doing for 25 years. (At the same time > I was frequently infuriated at the message "...does not support this property > or method", exactly because I ~didn't~ understand what was different about OO > coding.) > > Eventually a VBA programmer advised me a bit more, and I'm now an enthusiast, > about OO at least. Not so much about the Visual flavors of Basic itself, but > it was my introduction to OO and it is at least available on all Windows > machines and in all MS Office apps, which is handy. > > What confuses me (so far) is the concept of addressability in HLASM. Every > time I make a stab at writing my first assembler program I get a little > closer, but I'm still not there yet. In other assemblers I got quite > familiar with indirect and offset addressing - it isn't that - but what > exactly happens with the USING instruction still eludes me. > > --- > Bob Bridges, robhbrid...@gmail.com, cell 336 382-7313 > > /* Revenge can be bitter-sweet. But if you sit back and watch, karma can be > pure entertainment. -found on Facebook 2015 */ > > -----Original Message----- > From: IBM Mainframe Discussion List <IBM-MAIN@LISTSERV.UA.EDU> On Behalf Of > Tom Brennan > Sent: Sunday, September 18, 2022 00:59 > > As for programming, I seem to do better starting at the bottom, with > instructions, registers, PSW bits and such, and moving up from there. Higher > level languages and especially Object Oriented code tend to confuse me. > > ---------------------------------------------------------------------- > For IBM-MAIN subscribe / signoff / archive access instructions, > send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN -- Mike A Schwab, Springfield IL USA Where do Forest Rangers go to get away from it all? ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
