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You seem to know a lot about the system, thanks for sharing. Do you have any idea the reasoning behind the no nested libraries & objects can only have a 10(?) l

You seem to know a lot about the system, thanks for sharing. Do you have any idea the reasoning behind the no nested libraries & objects can only have a 10(?) letter name?

skissane 4y ago
Some of it is backward compatibility with earlier systems - S/36 and S/38 had roughly similar limitations. It is a design decision that dates back to the 1970s, and in the time they made it, they were hardly the only system to have made such a decision. Back then, truly hierarchical file systems were still a new idea - Unix was popularising it, Unix got the idea from Multics - it was primarily associated with research/academic systems and hadn’t yet spread much to commercial ones, which is where they were situating the product. On the other hand, S/38 adopted other highly novel research ideas, so why not this one? Another factor is the UI: 5250 and 3270 block terminals work really well with fixed width fields, they don’t have good support for arbitrary length ones. Fields can’t be scrolled - if the field has a maximum value length of 255 bytes, it has to take up that many bytes on the screen. That is likely a factor which discouraged them from longer names and multi-level hierarchy. OTOH, MVS datasets have max 44 character names. They are pseudo-hierarchical, with 4 levels of “qualifiers” then a name, each max 8 characters, separated by dots. So I don’t know why they didn’t do something closer to MVS-maybe they thought “we are not a mainframe we are midrange machines that’s overkill for us” The 8 or 10 character limit wasn’t uncommon for the 1970s. In those days, most Unix filesystems had a 14 character limit which is only a bit better. They could have enhanced the core system to support nested libraries and longer library and object names. It would have caused backward compatibly issues for older apps but there are workarounds for that, like Windows having both short names (8.3) and long names for files; they could have some system to make nested libraries look like unnested ones on an app-by-app basis. They decided never to make those investments-they decided to just slap a POSIX filesystem on the side and leave the core alone.
- sillywalk 4y ago
  That was my guess - the Green Screen thing, though I didn't know the fields couldn't scroll. It just seemed like with everything else sort of 'overkill' - 128bit address space - it would've been sort of an arbitrary amount. Thanks again for the info
  - skissane 4y ago
    > It just seemed like with everything else sort of 'overkill' - 128bit address space - it would've been sort of an arbitrary amount. It is kind of bizarre how they overkilled / went bleeding-edge in some areas but held back in others. It makes for a strange, retrofuturistic system

You seem to know a lot about the system, thanks for sharing. Do you have any idea the reasoning behind the no nested libraries & objects can only have a 10(?) letter name?

skissane 4y ago

Some of it is backward compatibility with earlier systems - S/36 and S/38 had roughly similar limitations. It is a design decision that dates back to the 1970s, and in the time they made it, they were hardly the only system to have made such a decision. Back then, truly hierarchical file systems were still a new idea - Unix was popularising it, Unix got the idea from Multics - it was primarily associated with research/academic systems and hadn’t yet spread much to commercial ones, which is where they were situating the product. On the other hand, S/38 adopted other highly novel research ideas, so why not this one? Another factor is the UI: 5250 and 3270 block terminals work really well with fixed width fields, they don’t have good support for arbitrary length ones. Fields can’t be scrolled - if the field has a maximum value length of 255 bytes, it has to take up that many bytes on the screen. That is likely a factor which discouraged them from longer names and multi-level hierarchy. OTOH, MVS datasets have max 44 character names. They are pseudo-hierarchical, with 4 levels of “qualifiers” then a name, each max 8 characters, separated by dots. So I don’t know why they didn’t do something closer to MVS-maybe they thought “we are not a mainframe we are midrange machines that’s overkill for us” The 8 or 10 character limit wasn’t uncommon for the 1970s. In those days, most Unix filesystems had a 14 character limit which is only a bit better. They could have enhanced the core system to support nested libraries and longer library and object names. It would have caused backward compatibly issues for older apps but there are workarounds for that, like Windows having both short names (8.3) and long names for files; they could have some system to make nested libraries look like unnested ones on an app-by-app basis. They decided never to make those investments-they decided to just slap a POSIX filesystem on the side and leave the core alone.

sillywalk 4y ago
That was my guess - the Green Screen thing, though I didn't know the fields couldn't scroll. It just seemed like with everything else sort of 'overkill' - 128bit address space - it would've been sort of an arbitrary amount. Thanks again for the info
- skissane 4y ago
  > It just seemed like with everything else sort of 'overkill' - 128bit address space - it would've been sort of an arbitrary amount. It is kind of bizarre how they overkilled / went bleeding-edge in some areas but held back in others. It makes for a strange, retrofuturistic system