OpenVMS vs. Unix

http://www3.sympatico.ca/n.rieck/docs/vms_vs_unix.html

by ddelony • 16 years ago

6 1 16 years ago

www3.sympatico.ca

bediger• 16 years ago

Perhaps the most un-biased comparison I've ever seen. It even includes a bit about different VMS filesystems, a neglected topic.

But I think this misses a lot of key points. You cannot compare operating systems without comparing a few key points:

1. What is a "process" (a.k.a "task", or "job") on this system? In traditional Unix, a process was an address space, a thread of control (the schedulable unit, another key comparison point), a signal mask, a (set of) signal handler(s), a UID, and effective UID, a group ID, and a set of file descriptors, and maybe some other stuff like priority. What's the equivalent in VMS? Nobody ever charts that out.

2. What's the lifecycle of a program? That's not the same as the lifecycle of a process in VMS, if I understand correctly. Contrast and compare. Extra points for complete explanation of starting a process (fork/exec vs CREATE$PROCESS or whatever VMS has).

3. What's the on-disk format of an executable file? How does the OS decide if it can execute a file? How does the OS decide to interpret a file (#!/usr/bin/env perl) or directly execute it?

4. How does a process do I/O? Synchronous or asynch? Are different classes of devices treated differently?

5. Does a file have a "type"? What, precisely does the "type" mean? On-disk format (fixed length records for example, or stream-of-bytes) or "a document's owner"?

OpenVMS vs. Unix

Related Stories