The Linux kernel, which is the core of the operating system that enables computers to function, is written in the C programming language rather than C++, despite the prevalence of the latter in the computing industry.
This is due to the fact that the C programming language is simpler and closer to the machine level, making it more efficient and secure, and for these reasons, it has been the preferred choice for creating a stable kernel.
The open-source nature of Linux also means that many developers can work on the codebase simultaneously, so using a language that is faster and easier to collaborate on makes more sense.
On the other hand, C++ has dynamically typed objects, a feature not present in C that provides a more efficient way to manage memory but makes it harder to debug as errors tend to be reported at runtime.
C is also a stricter language, which helps mitigate potential issues as the code is compiled at runtime, making C programmers more aware of potential pitfalls and in general, it is easier to learn the intimate details of the machine with C.