I've noticed a curious pattern to process identifier numbers on the z/OS system I'm working on (uname reports it as OS/390), they're either 1-4 digits long or 8 digits long but never in between. The high PIDs are a little over 16777216, 33554432 or 50331648.

So I dumped a bunch of them and printed them out in binary, they appear to fit this mask:


Is there a reason why process ids would use only 14 bits of an address space of 32, and/or what the big gap in the middle is all about?

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