It wasn't, so any C application that is more than a toy hello world with stdio, pings back into POSIX for any kind of meaningful work, that wants to stay cross platform.
Basically it the the C runtime library, that wasn't part of ISO.
I use JVM, .NET, Web and C++, not caring if the runtimes are bare metal or running on top of an OS, type 1 hypervisor, or whatever.
If you're downloading a JVM binary, you're missing out on the build step. It's C dependent, friend. How do you think that VM interfaces with the OS? Go on. Try it. ldd the java executable.
It's libc all the way down. C itself is a sort of "VM" specification utilized to create the tools to run the tools to build the tools that make other high level languages possible.
Unless you create something entirely custom in platform specific assembly, you're running on C at some level.
I'm not sure what you're trying to say. The Portable Operating System Interface (POSIX) is specified in an ISO standard, and basically specifies what a UNIX operating system's programmable interfaces are.
https://en.wikipedia.org/wiki/POSIX
POSIX also specifies stuff like "awk must be made available". Is that what you think the C programming language specifies?
POSIX is an IEEE standard (example [1]). POSIX defines the Operating System API. You can see the C implementation of this API here[2].
> so any C application that is more than a toy hello world with stdio, pings back into POSIX for any kind of meaningful work
Simply calling printf relies on writing to a file descriptor. A "Hello world" application on linux uses posix. ANY hello world application uses posix. Even your Java Hello world App will call into the posix APIs. `System.out.println` isn't magic. It calls into the C posix implementation.
If you want to do anything in any language (write to files, create threads, allocate memory, network communication), you need to go through the OS. POSIX is what defines that OS interface.
> I use JVM, .NET, Web and C++, not caring if the runtimes are bare metal or running on top of an OS, type 1 hypervisor, or whatever.
So you use POSIX, you just don't think about it.