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I understand that POSIX is a set of standards for a system interface.

I understand the RISC and CISC define a set of standard commands for a CPU.

To me, that sounds like the same thing. How are POSIX and RISC different/related?

Thanks in advance!

J Seabolt
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I understand that POSIX is a set of standards for a system interface.

More or less. It's a set of standards for the services an operating system provides, spanning parts of the kernel interface, standard libraries, and standard user utilities.

I understand the RISC and CISC define a set of standard commands for a CPU.

No. RISC and CISC they don't define anything, they describe. There are dozens of different instruction set families for CPUs, each one defined by a manufacturer or an industry group. For the sake of theoretical discussion, we sometimes call some of them RISC and some of them CISC.

To me, that sounds like the same thing. How are POSIX and RISC different/related?

They're not the same thing. It's not an apples to apples comparison. It's not even apples and oranges. It's more like apples and alpacas. They describe completely different things in completely different domains. Their commonality is "they have something to do with computers".

hobbs
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  • So there are different implementations of RISC and CISC. They are not standard. They are just a families of similar approaches to writing instructions. Does POSIX not define the interface? To me, that sounds very similar. – J Seabolt May 18 '21 at 16:18
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    @JSeabolt RISC & CISC are just families of CPUs (kind of machine instructions). POSIX is a programming interface to the OS at very much more abstract level (C for POSIX). Interface is a word used in many contexts. – Jean-Baptiste Yunès May 19 '21 at 11:02
  • @Jean-BaptisteYunès thank you for the polite, helpful answer – J Seabolt May 19 '21 at 17:23