How Does An Operating System Introduces The C Language To Write The Kernel

Does this introduction occurs at the NTLDR stage because it must be introduce, I mean isn't the Kernel written in C? I thought a computers only "known-bef开发者_开发问答ore" programming language was Assembly Language that is hard coded at the Microcode of the Processor?

The first operating systems were all written in assembly. The C Language was created because its first use case was the creation of UNIX. A C compiler was written to handle this code and produce the assembly that the system understands (compiler was written in assembly of course). The effect snowballs from there. We now have a more powerful system to write code so we can of course write better compilers and better software with a more high level approach and let the compiler do the work for us.

As far as Windows is concerned it was a rewrite of an operating system called QDOS which was written in C.

Sidenote: Operating systems still require assembly code to function as there are many hardware independent pieces of information required (for example CR2 read on page fault on x86). Bootloaders and BIOS (older ones) are written in assembly because they are very specific to the hardware and are required to setup things such as interrupts and the stack pointer.

C is a compiled language, as opposed to an interpreted language. C programs as well as the C runtime library are compiled into machine code, so they don't need any kind of runtime environment such as an interpreter or virtual machine to be loaded in order to execute.

The entry point of a compiled program (including a kernel) will call into its runtime library and perform any initialization required before executing the program, but this is all machine code.