Is it true that for programs written in C, the general assembly code?

Question

I read this by saying that

For example, for programs written primarily in C, parts that are in assembly language are usually used to optimize processor performance.

I have never seen a program written primarily in C, which also contains assembly code, at least not directly, like the source code. Just their Linux kernel example.

Is this statement true, and if so, how could it optimize processor performance?

Not just C code just translated into assembly code by the compiler?

Answer 1

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Answer 2

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