Indeed. The deeply alien nature of MVS and its descendants is fascinating. It's not only a difference in commands, but also the underlying concepts that don't map cleanly to concepts we got used to in Unix and Windows that causes a lot of confusion. For instance, a TSO user being unable to log in from different terminals at the same time confused me a lot until someone told me TSO users are not the same as Unix users. Also, a VM is not the same as a VMWare VM.
That, and datasets, which are not really hierarchical.
Yes there's a hierarchy (with . as a separator), but it's more naming convention than a description of the underlying filesystem. You can create projects.foo.code.bar without having any entity (like a Unix directory) for projects.foo first.
MCP, the only OS older than z/OS in active maintenance, even more alien than IBM’s, does more or less the same. It had at one time a hierarchical file system, but at some point they decided it was pointless and adopted a naming convention instead.
I was trying to get around it on SimH, with the B5500 version. Definitely deserves the name.
