After learning of the existence of XDAP in one of Dr. Rannie's SHARE presentations, I tried it out when I got home from SHARE. I found that XDAP is much, much easier to use than all the various pieces which must be interconnected correctly in order to use EXCP. XDAP is a macro which expands into code that builds a channel program and an IOB, then does an EXCP followed immediately by a WAIT. If you don't need to overlap any other processing in between the EXCP and the WAIT. then you can use XDAP, but you will still need an OPENed DCB and a DD statement. Its main drawback, in my opinion, is that only a small subset of all possible CCW commands are supported. But one can easily modify the macro's expansion and add code to build a much more sophisticated CCW chain. It's not quick and dirty, but it is quick and simple.
Bill Fairchild ----- Original Message ----- From: "David L. Craig" <[email protected]> To: [email protected] Sent: Monday, December 9, 2013 8:35:25 PM Subject: Re: "hexadecimal"? On 13Dec09:1528-0500, Gerhard Postpischil wrote: > On 12/9/2013 2:56 PM, Skip Robinson wrote: > > 2) That's a shame. Every programmer can benefit from familiarity > with the hardware - write a test program using EXCP to read a > multi-volume tape, or use XDAP to read a multi-volume DASD data set > with unknown block sizes. I remember Dr. Rannie talking about teaching Intro To Channel Programming using XDAP, not EXCP, so the students wouldn't have to worry about IOBs. He was challenged to come up with any other reason for using XDAP over EXCP. Of course, "real" MVS programmers use STARTIO (unless they cannot get their code into an APF library, of course). ;-) -- <not cent from sell> May the LORD God bless you exceedingly abundantly! Dave_Craig______________________________________________ "So the universe is not quite as you thought it was. You'd better rearrange your beliefs, then. Because you certainly can't rearrange the universe." __--from_Nightfall_by_Asimov/Silverberg_________________ ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
