Yes, so "only" in 99.9% of the cases, including all that matter most...

pjmlp · on June 28, 2012

So lets see:

- all the OS written before C ever existed, some still in use, even if in legacy deployments

- Symbian (written in C++)

- Mac OS X (is a mix of C++ and C)

- Windows is moving to C++ as the default systems language

- Native Oberon (Oberon)

- Lilitth (Modula-2)

- Spin (Modula-3)

- BeOS/Haiku (Written in C++)

- House (Haskell)

- MarteOS (Ada)

- IBM's OS/400 system (Written originally in Modula-2 and PL/MI)

- Singularity (Written in C# and C++)

- Lisp OS (Assembly and Lisp)

- Smalltalk Machines (Assembly and Smalltalk)

- Forth based OS for embedded systems

So one cannot expect that an OS will be always written in C.

quesera · on June 28, 2012

C++ is C with libraries to hide some stuff and add others. Removing C++ OSes from your list, I'd say that you're down to a vanishingly small percent of deployed systems. So yes, knowing C is important.

And I have never met a single person who knows any of your remaining languages who isn't at last passably familiar with C. I've never asked, but I don't think any of them would call their C knowledge unimportant or not useful.

batista · on June 29, 2012

You're seriously mentioning Lilith, Spin, Singularity, Lisp OS, MarteOS, Smalltalk machines et al to challenge the 99.9% thing?

OS X and Windows have some C++ (mostly wrappers) but otherwise are C.

pjmlp · on June 29, 2012

Yes, because even if they aren't that much used they do exist.

OS X drivers are written in C++, they are not wrappers over C.

http://developer.apple.com/library/mac/#documentation/device...

In Windows all the new APIs since Windows Vista are mostly COM (C++) based, including the new Userspace Driver Framework.

With Windows 8 this will increase, as Microsoft is moving to have C++ as their official systems language, by introducing WinRT as the new subsystem, and dropping support for anything besides C89.

Just because C is used a lot, you cannot say that all (even 99,9%) operating systems use it.

Actually I failed to mention the amount of operating systems that you may have running on your watch, vcr, radio, microwave, etc, which summed together are much more that the OS X, Windows, Linux base.