It's the correct definition and I don't know of anyone familiar with OS design that would claim C doesn't have a runtime. It very much does. So does C++. Every language does, except assembly.
It may feel like C doesn't have a runtime if you're only familiar with UNIX, because the C runtime is guaranteed to come with the OS there whereas other language runtimes are optional and thus more visible. But every language has a runtime.
It may feel like C doesn't have a runtime if you're only familiar with UNIX, because the C runtime is guaranteed to come with the OS there whereas other language runtimes are optional and thus more visible. But every language has a runtime.