Month: November 2024

Take a few minutes to review an idea rather than an instruction today. In this article I discuss how to code prewritten IBM macros in Standard, List, and Execute formats, and why you might want to. The article comes with a program if you want to experiment with these ideas.

Here is the grande version of the instruction we reviewed last week: CRB. Read about it here.  Watch it happen in Visiblez here. Have a great weekend!

Get two instructions in one with Compare Registers and Branch (CRB). And this instruction is related to others you can easily pick up. Read about CRB here, and watch the Visiblez video here.

One thing that’s great about learning IBM assembler is that if you master one instruction, you often learn a handful of others by association. That’s the case with AGSI – Add Grande Storage Immediate, which is related to ASI. The G in AGSI suggests a register might be involved, but don’t be fooled. Both operands are in storage. The first operand is eight bytes – the size of a grande register,the second operand is a single immediate constant that occupies the second byte of the instruction. Get the details here. Watch the instruction in action with Visiblez here.

Dear Reader,

I’m not punctilious. I wish I were. It is a goal. The recent writeup of ASI contained a paragraph that didn’t make a bit of sense – too much copying and not enough thought. I’ve corrrected it and vow to do better. Apologies.

David

This little instruction comes with two surprises. I’ll tell you about one: It allows us to add two binary fields without a register! We could always add two packed fields without a register, but now we can do that with 2’s complement fields in memory. You’ll have to watch the ASI video to learn the other surprise.

So, have a cup of coffee, and review this humble but interesting little instruction.

Read about ASI here. Watch the Visiblez video here.

I’m creating new articles on my website in alphabetical order, and I’m on the A’s. There are numerous add instructions to choose from. Today’s instruction is AGF and is similar to AGI which we have already reviewed. You can find the writeup here, and you can watch the instruction in action using Visiblez here.