Welcome to my site! I’ve been coding IBM mainframe assembly language since the late 1970’s. Over the years I’ve taught thousands of programmers, both in a university setting and as a corporate trainer for Fortune 500 companies, how to write assembler programs. Perhaps I can help you, too.
What you will find here:

  • A wealth of written material covering System/z assembler concepts
  • A freeware object code interpreter called VizibleZ that I developed as a tool for teaching assembler language
  • A video course (under development) that will teach you how to code in assembler
  • A weekly blog about all things Assembler

Dr. David E. Woolbright

5 thoughts on “Welcome”

  1. Mr. Wizard

    I was a wondering why, the object module to be loaded into Visible/Z must be in readable ASCII. In z390 everything is in EBCDIC and the files must be Converted/loaded after processing them into ASCII readable format.

    Has anybody noticed the z390 HLASM is exactly like the mainframe format
    and load and object format are maintained as in System/Z

    It would be KOOL to just load a z390 file as is

    James Francis Cray

    1. Dumping an object module directly into VizibleZ was my initial thought, but after using VisibleZ in the classroom, I found it helpful to be able to write code snippets in class to illustrate one or two instructions at a time. The easiest way to do this from a PC, was to use a text editor and type in the object code I created on the fly. I found this to be a good exercise for students, too. It made them think clearly about base/displacements. It would be possible to add a feature for reading object modules into memory directly. If it would be helpful, let me know.

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