Category: IBM Champion

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A place for everything, and everything in its place. In assembler, that means that the things we define require proper alignment. This short paper discusses alignment for code and data, and how to get it.

I’ve added an introductory section on debugging to the main page. Currently, there are four videos and four abending programs that cover abends S0C1, S0C4, and two versions of S0C7. You will have to add some JCL for your system. I’ve included the data sets the programs process. I will add some more videos for other abends later.

Multiply Grande (MG) is the sister instruction of Multiply(M) and produces produces 128-bit products in an even/odd register pair. Ususally the result we are looking for is in the single, odd, grande (64-bits) register. That presents a problem: How do we convert a 64-bit product in a grande register to packed-decimal? It’s not obvious and requires a bit of mathematical know-how. This article shows you the assembler code that will do the conversion, and points to an explanation.

It’s been a few weeks since I’ve posted. Life intervenes occasionally. This post is for a Multiply (Fullword) instruction which has an RXY-a instruction format providing a long displacement. This instruction is well worth a look, if you consistently reach for (M) when multiplying fullwords. You can find the short article for MFY here.

Ready to tackle programs that can reach above the bar? As they say in Red Stick, There is beaucoup storage there waiting for you. In this video, you will learn how to call a subroutine that switches to 64-bit addressing to create 10 megabytes of storage above the bar. Think of what you can do with that amount of storage – Read an entire file into memory – build a data structure for all of your records. Besides the video, there is a working main program and a subroutine you can use to get started. 

These are easy to pick up – handy, too, if you want to write 64-bit addressing programs. If you are changing addressing modes from 31 to 64, say, you have some 31-bit addresses that need to be expanded to 64-bit. Well, these are the instructions you need. Read about them here and here.

This week I am in lovely Vilnius with my son before starting a week of assembler training. I’ll post some pictures below. The castle is in Trakai, a short drive outside the city. The bust is of Frank Zappa, Rock on Vilnius!

On a different note, Amit Sharma was kind enough to interview me for his wonderful Tech Sharmit podcast.You can listen to the interview here. You can catch Amit on YouTube here. Thanks again, Amit!

There is still time to register for the free virtual conference. Starts soon. Read about it here: https://ibmzday.bemyapp.com

Multiply Single (MS) provides another way to multiply binary integers using a single register. Read about it here.