CBT Tape

CBT Tape is an open library of free software distribution for the IBM mainframe Multiple Virtual Storage (MVS) and OS/390 and z/OS operating system environments that continues to evolve to meet today’s modern needs.

The roots of the open source movement trace back to SHARE but much of that initial collaboration came together with the CBT (Connecticut Bank and Trust) Tape in 1975.  Arnold Casinghino established the CBT Tape when people started using Multiple Virtual Storage (MVS). At that time, there were a few “user forums” for communities to discuss software challenges and improvements. Arnold adopted that open mentality and worked with the hundreds of contributors to continually update the tape through 321 versions over 15 years. The reins were handed over to Sam Golob, who has helped cultivate contributions and update the CBT Tape for the last 30 years. 

CBT Tape is an open library of free software distribution for the IBM mainframe Multiple Virtual Storage (MVS) and OS/390 and z/OS operating system environments, that continues to grow and get updated. With each iteration of these tapes, more new and ingenious tools and examples became available. As a part of the Open Mainframe Community, CBT Tape benefits from a broader ecosystem that will raise awareness for this extensive library and introduce it to a new generation.

All updates, codes and news can be found on the CBT Tape community website – http://www.cbttape.org/


What is tape?

There are many kinds of magnetic media.  Mainframe magnetic data tapes have long been the home of the CBT Tape because this was the format used to store large amounts of information off-line and to move it from site to site.  However, today, the CBT Tape is distributed in the real world from the website:  www.cbttape.org.

Why do you still create tapes?

We distribute tapes from our website.  CBT Tape is still distributed and released using a version system patterned from the tape model, for several reasons.  The “release number” of a “tape” provides a consistent reference for everyone around the world.  If you are told that utility xyz from File 555 will solve your problem and it was added at CBT tape V421 then you instantly know if you have it and where to get it. But practically speaking, you should try to get your utilities from the latest “tape version”, unless you’re running an antiquated version of MVS, and you need an old version of the utility.


The tape/version distribution provides persistence that a simple on-line download area does not.  The tape was copied (usually several hundred of any given version were circulated worldwide) and distributed widely so that it is unlikely it would ever be completely lost if something were to happen to the people who are currently maintaining the tape and the web site.  The tape format along with a system we use for making updates allows us to master a new tape at a friendly site using limited DASD.