SAV. MELLOR
Retired, Previously Application Programming, Systems Programming, Project
Management at Rolls Royce and Various roles at Amdahl.

Company—
Previously Rolls Royce, Derby, UK and Amdahl (UK)

Years in IT—
48 including 10 in retirement—you never really quit!

My first mainframe job—
In 1966, I joined Rolls Royce (the aero engines, not the cars, so no free samples!) as an application programmer on their brand new S360/50, running OS/360 PCP. Rolls Royce had chosen to adopt the then new PL/1 language for all commercial application work. For the PL/1 fans, this was the Level F compiler that had only Stream I/O; Record I/O was a couple of releases away. My first job was as part of a team translating a production scheduling system (ERP in today’s terminology) from the full to capacity IBM 7074 to the new S/360. 7074 Autocoder to PL/1 is not an easy translation, to say the least.

After a few years in system development, I moved to the software group, where I was responsible for the language support, PL/1 for commercial and a mixture of PL/1 and Fortran for Engineering.

In the mid 1970s, I moved on to a more hardware base when we decided to install an IBM 3850 Mass Storage System, initially a B3, upgrading to a twin A4 and adding a separate A3 system—we liked these machines!

After a spell in more general project management, I decided that my interest lay more in IT than in aero engines and joined a mainframe manufacturer, Amdahl and we’ll leave it at that, since this is an IBM forum.

My favorite mainframe attribute—
As the “Highlander” says, “There can be only one” and that one for me has to be Architectural Compatibility. As above, my first role was converting a major system from an old machine to the next incompatible generation. This was the second time Rolls Royce had done this, the previous time was from an IBM 650 to the 7074. I truly believe that if this had been allowed to go on, there would have been a point where conversion of old systems would have taken longer than the life of the new machine.

With the System/360, IBM made a commitment that providing programs were written in problem state, in accordance with the Principles of Operation and contained no model dependent or timing dependent features, they would guarantee that the same program would run unchanged on all subsequent versions of the S/360 architecture machines and their derivatives. This commitment has been kept through the intervening 50 years to today’s zEnterprise systems, a great achievement.

My favorite mainframe memory—
There are just too many but, leaving aside my time with Amdahl, I’ll mention just two.

The first was successfully developing a VM/370 CMS virtual machine to drive the 3850 MSS directly for systems programming purposes, despite IBM saying it couldn’t be done. We didn’t understand “couldn’t” at Rolls Royce!

The second was the privilege of heading up one of the best OS systems programming groups in the world.
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